electric-field contact-less sensing...
TRANSCRIPT
MC33794 (Electric-Field Sensing IC)
freescale.com
APPEFIELDRM Rev. 009/2006
Designer Reference ManualElectric-Field Contact-less Sensing System
Electric-Field Contact-less Sensing System, Rev. 0
2 Freescale Semiconductor
Electric-Field Contact-less Sensing SystemDesigner Reference Manual
by: Jozef Prokopovic Freescale Czech Systems Laboratories Roznov pod Radhostem, Czech Republic
To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify that you have the latest information available, refer to http://www.freescale.com.The following revision history table summarizes changes contained in this document. For your convenience, the page number designators have been linked to the appropriate location.
Revision History
Date RevisionLevel Description Page
Number(s)
09/2006 0 Initial release 52
Table of Contents
Chapter 1 Introduction
1.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3 About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 2 Theory
2.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2 E-Field Sensing: An Alternative Solution to Control Panel Applications . . . . . . . . . . . . . . . . . . 112.3 Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Chapter 3 System Concept
3.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2 System Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.3 Application Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Chapter 4 Hardware
4.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.2 System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.3 Application schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4 Hardware design considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4.1 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4.2 E-Field Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4.3 Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.4.4 Serial Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.4.5 Op-Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.4.6 MSDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.4.7 H-Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.4.8 Buzzer circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.4.9 Jumpers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.4.10 Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 5 Software
5.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.2 Software Design Consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
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5.3 Main Data Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.4 Firmware Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355.6 FreeMASTER Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Chapter 6 Application Setup
6.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376.2 Setting Up the Demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376.3 Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.4 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.5 Modes of E-Field Demonstrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.5.1 Touch Pad (Keyboard) Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396.5.2 Slider Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406.5.3 Water Pump Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406.5.4 Water Slider Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416.6 Demo System Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416.7 Starting the Demo System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426.7.1 Step 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426.7.2 Step 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436.7.3 Step 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446.8 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Appendix A. E-Field Contactless Sensing Demonstrator
Schematics
Appendix B. E-Field Contactless Sensing Demonstrator
Bill of Material
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List of Figures
Figure 1-1 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Figure 1-2 E-Field Contactless Sensing Demonstrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Figure 2-1 Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 3-1 Water Column. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Figure 3-2 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Figure 3-3 Minimizing fringing fields with SHIELD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Figure 4-1 SPI communication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Figure 4-2 H-Bridge circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Figure 4-3 Default jumpers configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Figure 4-4 Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Figure 5-1 State Diagram - General Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Figure 5-2 Main Data Flow Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Figure 5-3 Touch Pad Mode Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Figure 5-4 Slider Mode Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Figure 5-5 Water Pump Mode Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Figure 5-6 Water Slider Mode Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Figure 5-7 TIM Overflow Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Figure 5-8 FreeMASTER Software Control Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Figure 6-1 E-Field (Touch Pad Board, Water Level Board) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Figure 6-2 E-Field demo (TPB connected with WLB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Figure 6-3 Mode Selection Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Figure 6-4 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Figure 6-5 Slider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Figure 6-6 Pump Up (Down) Button. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Figure 6-7 Water Slider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Figure 6-8 Main Window of FreeMASTER Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Figure 6-9 Options Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Figure 6-10 Open Project Window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Figure A-1 Schematics “A” of Touch Pad Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-2Figure A-2 Schematic “B“ of Touch Pad Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3Figure A-3 Schematic of Water Level Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-4
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List of TablesTable 4-1 Electrode Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Table 4-2 Truth Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Table 4-3 Jumpers Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Table 4-4 J3 (J1) connector of TPB (WLB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 4-5 J4 (J2) connector of TPB (WLB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 4-6 J2 connector of TPB (DB9 female) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 5-1 Main, Initialization, FreeMASTER Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Table 5-2 Calibrate Electrodes, Read Values, Read Electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Table 5-3 Read Delta, Verify Electrodes, Display Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Table 5-4 Bar Graph, Water Bar Graph, Water Slider Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Table 5-5 Rotate Up, Rotate Down, Stop Rotate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Table 5-6 Beep On, Beep Off, Auto Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Table 5-7 SendSPI, SendpSPI, Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Table 5-8 GetTick, Beeper, Count . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Table 5-9 Slider, Water Slider, Measure Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Table 5-10 Water Level, Verify Key, Verify Mode Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Chapter 1 Introduction
1.1 Contents
1.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3 About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.2 Introduction
This reference manual describes the design and features of an Electric-Field Contact-less Sensing System based on Freescale’s MC33794 (Electronic Field Imaging Device).
The MC33794 is intended for cost-sensitive applications where non-contact sensing of objects is desired. When connected to external electrodes, an electric field is created. The MC33794 is intended to detect objects in this electric field. The IC generates a low-frequency sine wave, adjustable by using an external resistor, and is optimized for 120 kHz. The sine wave has very low harmonic content to reduce harmonic interference.
The MC33794 also contains support circuits for a microcontroller unit (MCU) to allow the construction of a two-chip E-field system.
MC33794 features
• Supports up to nine Electrodes and two References or Electrodes
• Shield Driver for Driving Remote Electrodes Through Coaxial Cables
• +5.0 VDC Regulator to Power External Circuit
• ISO-9141 Physical Layer Interface
• Lamp Driver Output
• Watchdog and Power-ON Reset Timer
• Critical Internal Nodes Scaled and Selectable for Measurement
• High-Purity Sine Wave Generator Tunable with External Resistor
• Response Time Tunable with External Capacitor
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Introduction
Typical Applications
• Appliance Control Panels and Touch Sensors
• Linear and Rotational Sliders
• Spill Over Flow Sensing Measurement
• Refrigeration Frost Sensing
• Industrial Control and Safety Systems Security
• Proximity Detection
• Touch Screens
• Liquid Level Sensing
The Electric-Field Contact-less Sensing System is based on this MC33794 device. This application is controlled by a low cost 8-bit microcontroller, the MC68HC908QB8. This E-Field demonstrator detects human touch through glass and measures the level of water in a water column. An illustration of the system configuration is shown in Figure 1-1 System Configuration.
The Electric-Field Contact-less Sensing System has the following features:
• Detecting human touch (Touchpad, Slider) and water level detection (Water pump, Water slider) using Freescale MC33794 E-Field sensor
• Freescale MC68HC908QB8 8-bit microcontroller
• Freescale MC33993 MSDI (Multiple Switch Detection Interface) – driving LEDs– interfaces directly with the microcontroller using SPI protocol
• Freescale MC33886 H-Bridge used as a water pump motor driver
• Connection with PC via RS232
• Option of installing a Dual Op-Amp to amplify weak E-Field signals
• 7-segment numeric LED display, LED Bar-Graph
• Input supply voltage +12V DC / 2A
• Audio Buzzer
Figure 1-2 Electric-Field Contact-less Sensing System shows the board layout with description of the components.
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About this Manual
Figure 1-1. System Configuration
1.3 About this Manual
Key information can be located at the following location in this manual:
• Setup instructions are found in Chapter 6 Application Setup
• Pin-by-pin descriptions are contained in Tables 4-4 to 4-6
• For those interested in the reference design aspects of the board’s circuitry, a description is provided in Chapter 5 Software
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About this Manual
Figure 1-2. Electric-Field Contact-less Sensing System
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Chapter 2 Theory
2.1 Contents
2.2 E-Field Sensing: An Alternative Solution to Control Panel Applications . . 112.3 Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 E-Field Sensing: An Alternative Solution to Control Panel Applications
Human touch can be a useful tool. Control panels, appliances, heavy machinery, toys, lighting controls, and anything that has a mechanical switch or push button requires some sort of human interaction to operate. Traditionally, push buttons are made from mechanical switches and/or multi-layer resistive touch pads that can deteriorate and become less dependable over time. This is because most of these switches require physical displacement and pressure, and are susceptible to wear-out, contact bounce, corrosion and arcing.
The MC34940/MC33794 Electric Field Imaging devices from Freescale offers an alternative to mechanical push buttons for control panel applications. The MC34940/MC33794 Integrated Circuits (IC) contain the circuitry necessary to generate a low level electric field and measure the field loading caused by objects moving into or out of the field. It is ideal for applications that require non-contact sensing, proximity detection, and three-dimensional e-field imaging. The ICs integrate support for a microcontroller and seven to nine electrodes, which can be used independently to determine the size or location of an object in a weak electric field.
With the MC34940/MC33794, membrane switches and resistive touch pads can be replaced by an array of touch pads consisting of conductive electrodes embedded beneath an insulating surface. Since it has the capability of sensing touch and proximity through the insulating sur-face, without direct electrical contact with the electrode metal, problems of wear, contamination, and corrosion are eliminated.
Furthermore, one of the MC34940/MC33794 key features that surpasses simple capacitive-based sensors is its on-board shield driver. Touch pads do not have to be combined and located in one centralized location. With proper shielding, coaxial cables or PCB layers can be used to connect remote touch pads up to a few meters away, while obtaining measurements as accurately as if the touch pads were directly connected to the IC. The MC34940/MC33794 does this by driving a signal on the shield of the coax, or a PCB trace, which closely follows the signal conductor voltage. The current which flows through the electric field between two conductors is proportional to the voltage difference between them. With little or no voltage difference, there is little or no current flow between the electrode conductor and the shielding trace or coax shield.
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Principle of Operation
2.3 Principle of Operation
The MC33794 is intended for use in detecting objects using an electric field. The IC generates a low radio frequency sine wave. The frequency is set by an external resistor and is optimized for 120 kHz. The sine wave has very low harmonic content to reduce potential interference at higher harmonically related frequencies. The internal generator produces a nominal 5.0 V peak-to-peak output that is passed through an internal resistor of about 22 kΩ. An internal multiplexer routes the signal to one of 11 terminals under the control of the ABCD input terminals. A receiver multiplexer simultaneously connected to the selected electrode routes its signal to a detector, which converts the sine wave to a DC level. This DC level is filtered by an external capacitor and is multiplied and offset to increase sensitivity. All of the unselected electrode outputs are grounded by the device. The amplitude and phase of the sinusoidal wave at the electrode are affected by objects in proximity. A “capacitor” is formed between the driving electrode and the object, each forming a “plate” that holds the electric charge. The voltage measured is an inverse function of the capacitance between the electrode being measured, the surrounding electrodes, and other objects in the electric field surrounding that electrode. Increasing capacitance results in decreasing voltage. The value of the series resistor (22kΩ) was chosen to provide a near linear relationship at 120 kHz over a range of 10pF to 70pF. While exploring applications using E-Field products, it is always useful to approach the problem using the capacitor model.
Figure 2-1. Principle of Operation
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Chapter 3 System Concept
3.1 Contents
3.2 System Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 System Specification
The main goal of this demo board is to present features of the MC33794 E-Field sensor product. It is an application dedicated to sense human touch and liquid level. Every button and slider senses human touch and proximity. Water level is measured in the water column by copper electrodes fixed on the column from the outside.
Figure 3-1. Water Column
Non-Metallic Container(Water Column)
Conductive Bands(Copper Electrodes)
Liquid(Water)
E-Field
Non-Metallic Container(Water Column)
Conductive Bands(Copper Electrodes)
Liquid(Water)
E-Field
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 13
Application Description
This demo consists of two main boards: Touch Pad Board and Water Level Board. Interfacing is implemented through connectors. There is also the option of installing a Dual Op-Amp to amplify weak E-Field signals if required.
The E-Field demonstrator can work in 4 modes: Touch Pad, Slider, Water Pump and Water Slider.
A mode selection electrode is used to switch the demo to another mode.
The FreeMASTER GUI is used to bring a visual demonstration of electrode behavior during the sensing of human touch or water level.
3.3 Application Description
Figure 3-2 shows a block diagram of the application.
Figure 3-2. Block Diagram
The main application consists of Freescale ICs such as
• MC33794 Electric Field Sensing Device
• MC68HC908QB8 8-bit Microcontroller (8K FLASH)
HC908QB88-bit MCU
MC33794E-field
Electrode select (A,B,C,D)
LEVEL
E-fieldelectrodes
PWM/direction
SPI
+5V Vdd
+12Vpowersupply
FreeMASTERRS232 PC connection
MMC33886H-bridge
Water pump motor
Shield
MC33993MSDI
. . . . . .
LED’s Display
Buzzer
Dual Op-Amp
FreeMASTER
SW for SCI
HC908QB88-bit MCU
MC33794E-field
Electrode select (A,B,C,D)
LEVEL
E-fieldelectrodes
PWM/direction
SPI
+5V Vdd
+12Vpowersupply
FreeMASTERRS232 PC connection
MMC33886H-bridge
Water pump motor
Shield
MC33993MSDI
. . . . . .
MC33993MSDI
. . . . . .
LED’s Display
Buzzer
Dual Op-Amp
FreeMASTER
SW for SCI
Electric-Field Contact-less Sensing System, Rev. 0
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Application Description
• MC33993 Multiple Switch Detection Interface
• MC33886 H-Bridge
MC33794 is intended for sensing the electric field generated near the electrodes. This application uses nine electrodes (buttons and conductive bands) and one reference electrode (mode selection button). A second reference electrode pin is connected through a capacitor to the ground. Just one of these electrodes can be selected at a time for measurement. All of the other unselected electrodes are grounded by an internal switch, apart from the reference electrodes. Fringing fields were reduced by placing a copper layer connected to the SHIELD pin at the bottom and around the electrodes at the top of the PCB (Figure 3-3).
Figure 3-3. Minimizing fringing fields with SHIELD
The detected, amplified and offset representation of the signal voltage on the selected electrode is connected through the LEVEL pin to the MCU A/D convertor. Pins A, B, C, D are 5V logic pins controlled from the MCU, intended to select appropriate electrodes. The converted value is stored, read and displayed by the FreeMASTER SW using serial communication (RS232).
The application is powered by +12V DC. The power supply of +5V DC for the MCU and other devices is provided by the MC33794’s +5.0V DC internal voltage regulator (Vcc).
The MSDI device (MC33993) drives the LEDs and the 7 segment display and is controlled by SPI commands from the MCU through SPI communication protocol. The LEDs and display are connected directly to the MSDI SG or SP pins.
The MC33886 is a monolithic H-Bridge. In this application it is used as a controller of the water pump DC motor. The MCU generates 6.25kHz PWM signal to drive the MC33886. The PWM duty cycle is decreased or increased by the MCU to provide the desired speed for pumping the water.
In addition, a visualization of several variables via computer has been implemented. FreeMAS-TER software is used for the purpose of graphical visualization, communicated via SCI protocol. The FreeMASTER SCI software is also implemented in the MCU to allow communication between the application and the PC. The communication speed is 57600Baud.
Button
Copper Plates connected to SHIELD pin
Button
Copper Plates connected to SHIELD pin
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 15
Chapter 4 Hardware
4.1 Contents
4.2 System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.3 Application schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4 Hardware design considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.4.1 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4.2 E-Field Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.4.3 Microcontroller. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.4.4 Serial Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.4.5 Op-Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.4.6 MSDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.4.7 H-Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.4.8 Buzzer circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.4.9 Jumpers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.4.10 Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2 System Overview
The demo consists of two boards - TOUCH PAD BOARD (TPB) and WATER LEVEL BOARD (WLB). The boards are attached to each other. Refer to Figure 6-1 and Figure 6-2.
The TPB contains:
• E-Field chip (MC33794)
• MCU (HC908QB8)
• RS232 connection (MAX202, DB9 female)
• Dual Op-Amp (LM358 - optional)
• Power supply jack (+12 VDC)
• Buzzer circuitry
• Buttons (keyboard, slider, mode selection button)
The WLB contains:
• Water column with copper electrodes
• H-Bridge (MC33886)
• MSDI (MC33993)
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Application schematics
• Water slider
• LED Bar, 7 segment LED Display
For a block diagram, refer to Figure 3-2.
4.3 Application schematics
Figure A-1and Figure A-2 are schematics of the Touch Pad Board. Figure A-3 is a schematic of the Water Level Board.
4.4 Hardware design considerations
4.4.1 Power Supply
The board is powered by a +12 VDC external supply through jack J1 on the Touch Pad Board. An internal voltage regulator in the E-Field IC provides +5.0V DC for remaining circuits.
4.4.2 E-Field Sensor
MC33794 is powered by a +12 VDC from an external power supply. The +12V DC applied to the VPWR pin is converted into the regulated voltages needed to operate the part. It is also converted into +5.0V DC to power the MCU and external devices.
The level detected from output pin LEVEL is connected directly to the MCU A/D convertor, optionally through the Dual Op-Amplifier.
A specific electrode is selected by the A, B, C, D pins Table 4-1, which are controlled from the MCU.
Table 4-1. Electrode Selection
PIN/SIGNAL D C B A
Source(internal) 0 0 0 0
E1 0 0 0 1
E2 0 0 1 0
E3 0 0 1 1
E4 0 1 0 0
E5 0 1 0 1
E6 0 1 1 0
E7 0 1 1 1
E8 1 0 0 0
E9 1 0 0 1
REF_A 1 0 1 0
REF_B 1 0 1 1
Internal OSC 1 1 0 0
Internal OSC after 22kΩ 1 1 0 1
Internal Ground 1 1 1 0
Reserved 1 1 1 1
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Hardware design considerations
Resistor R2 determines the operating frequency of the oscillator. R2 = 39kΩ to provide an operating frequency = 120kHz.
Electrodes (E1- E9) are used as single button electrodes on the Touch Pad Board. The slider on the Touch Pad Board is made from electrodes E6 and E7. The slider on the Water Level Board is made from E8 and E9. Five conductive bands on the water column are connected as electrodes E1- E5. The SHIELD pin is connected to the shield copper layer and is also tied to connector J3 for Water Level Board purposes. REF_A pin is used as a single (Mode Selection) electrode to switch between all modes. To avoid REF_B pin floating, this pin is connected through C19 to ground.
The VCC pin provides +5.0V DC for the remaining circuits. C4 and C5 are connected to this pin to provide a stabilized voltage.
4.4.3 Microcontroller
The system is based on an MC68HC908QB8, 8-bit, low cost microcontroller, powered by a +5V DC from the E-Field sensor. The MCU selects each specific E-Field channel, reads output from the E-Field sensor and takes appropriate action. It also sends commands to the MSDI to drive LEDs, toggle the Buzzer ON or OFF, handle interfacing with the H-Bridge (driving the water pump), and performs serial communication with the implemented FreeMASTER software via RS232.
As soon as the MCU is programmed with the serial bootloader, the MCU memory can be modified in-circuit via the serial port (see AN2295/D Developer’s Serial Bootloader for M68HC08 and HCS08 MCUs).
Detected levels are fed from the E-Field to the MCU A/D channel. This A/D converter works in 10-bit resolution mode.
The PWM output from the microcontroller, combined with direction signals, drives the water pump motor through the H-Bridge.
No external crystal or oscillator is required, as the MCU runs on an internal oscillator.
Pins PTA 0, PTA1, PTA4, PTA5 select each specific E-Field channel (see Table 4-1) PTA0 = A, PTA1 = B, PTA4 = C, PTA5 = D.
4.4.4 Serial Communication
Serial communication uses the ESCI module of the QB8 microcontroller, a MAX202 and a DB9 connector. The E-Field demonstrator application implements software serial communication and FreeMASTER (formerly known as PC Master) code in order to demonstrate the sensing process. Serial communication is fully controlled by the implemented FreeMASTER software. The details are given in the separate Freescale Application notes (see AN2395 - PC Master Software Usage and AN2471 - PC Master Software Communication Protocol Specification).
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Hardware design considerations
4.4.5 Op-Amp
The Touch Pad Board includes footprints for Op-Amp components. This amplifier was considered to provide higher sensitivity to the signal read by the MCU A/D convertor. Measured results have shown that this Op-Amp is not necessary in this application.
4.4.6 MSDI
The 33993 Multiple Switch Detection Interface is designed to detect the closing and opening of up to 22 switch contacts. The switch status, either open or closed, is transferred to the microprocessor unit (MCU) through a serial peripheral interface (SPI).
Figure 4-1. SPI communication
In this particular application, the MSDI drives LEDs D1- D14 and the seven segment display DIS1. D1 - D14 are connected to SG pins and DIS1 is connected to SP pins (SP pins are switched to the battery, SG pins are switched to the ground). In this application we use the internal configurable current sources. 2mA current sources are used for the LEDs, and 16mA current sources are used for DIS1.
The MSDI communicates with the MCU using just a three wire (MOSI, SCLK and CSB) SPI because no feedback from the MSDI is required (Figure 4-1).
4.4.7 H-Bridge
Freescale’s MC33886 is a monolithic H-Bridge ideal for DC-motor and bi-directional thrust solenoid control. The 33886 is able to control continuous inductive DC load currents up to 5.0A. The water pump motor used in the E-Field demo is a 3.0A load. Output loads can be pulse width modulated (PWM-ed) at frequencies up to 10kHz.
The H-Bridge can operate in several modes but we are using just two of them (Table 4-2):
• Forward
• Reverse
HC08QB8 SPI master
MOSI
SCLK
CSB
SPI Shift register
MC33993 MSDI SPI slave
MOSI
SCLK
CSB
SPI Shift register
HC08QB8 SPI master
MOSI
SCLK
CSB
SPI Shift register
MC33993 MSDI SPI slave
MOSI
SCLK
CSB
SPI Shift register
Electric-Field Contact-less Sensing System, Rev. 0
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Hardware design considerations
The DC motor is connected through the OUT1 and OUT2 terminals to the internal power MOSFET H-Bridge of the IC. IN1(direction) and IN2 (PWM signal) are input control terminals used to control OUT1 and OUT2 (see Figure 4-2).
Figure 4-2. H-Bridge circuitry
4.4.8 Buzzer circuitry
The buzzer is controlled directly by a GPIO pin of the MCU (PTB7). A MOSFET transistor is used to switch the buzzer ON or OFF.
4.4.9 Jumpers
The configuration jumpers in the E-Field demonstrator are JP1 and JP2.
JP1 selects between two values of LP_CAP (Low-Pass Filter Capacitor), 10nF or 1nF. A capacitor on this pin forms a low pass filter with the internal series resistance from the detector to this pin. This pin can be used to determine the detected level before amplification or offset is
Table 4-2. Truth Table
Device StateInput Conditions
Fault Status Flag
Output States
D1 D2 IN1 IN2 FS OUT1 OUT2
Forward L H H L H H L
Reverse L H L H H L H
HC08QB8MC33886H-Bridge
DCmotor
OUT1
OUT2FSD1D2+5V
IN1
IN2TCH2
PTA3direction
PWM (6.25kHz)
HC08QB8MC33886H-BridgeMC33886H-Bridge
DCmotorDC
motor
OUT1
OUT2FSD1D2+5V
IN1
IN2TCH2
PTA3direction
PWM (6.25kHz)
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Hardware design considerations
applied. A 10 nF capacitor connected to this pin is recommended. More capacitance will increase the response time unnecessarily.
JP2 selects whether the input to the MCU A/D convertor is fed directly from the MC33794 output pin LEVEL or if the output signal is first amplified by the op-amp. The op-amp is not populated in this revision of the board, therefore JP2 in position 2-3 has no meaning.
Figure 4-3. Default jumpers configuration
4.4.10 Connectors
The Touch Pad Board (TPB) and Water Level Board (WLB) are connected together with connectors J3, J4 on the TPB (Figure A-1, Figure A-2), and J1, J2 on the WLB (Figure A-3). J3 on the TPB matches up with J1 on the WLB. J4 on the TPB matches up with J2 on the WLB.
Electrode signals and Shield signal are grouped together on the J3 connector of the TPB and the J1 connector of the WLB. SPI signals, H-Bridge control signals, power supply and GND are
Table 4-3. Jumpers Configuration
Jumper Position Description
JP1 1-2C7 (1nF) connected to
LP_CAP pin
JP1 2-3C8 (10nF) connected to
LP_CAP pindefault
JP2 1-2LEVEL pin connected
directly to MCUdefault
JP2 2-3LEVEL pin connected
through Op-Amp to MCU
1 3
1
2JP1
3 2
JP2
1 3
1
2JP1
3 2
JP2
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Freescale Semiconductor 21
Hardware design considerations
grouped on the J4 connector of the TPB and on the J2 connector of the WLB. Pin assignments are shown in Figure 4-4 Connectors.
Figure 4-4. Connectors
1 23 45 67 89 10
14131211
19
15 161817
212022
23 242625
Shield
ShieldShield
ShieldShield
Shield
Shield
Electrode 9
Electrode 5Electrode 8
Electrode 3Electrode 4
Electrode 1Electrode 2
J3 connector of TPBJ1 connector of WLB
1 23 45 67 89 10
14131211
19
15 161817
212022
23 242625
GND
J4 connector of TPBJ2 connector of WLB
MOSICSB
+5V
PTA3PTB6/TCH2
SCLK
+5V
+12V
1
2
3
4
5
6
7
8
9GND
RXD
TXD
J2 connector of TPBDB9 female
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Hardware design considerations
Pin descriptions are listed in Table 4-4, Table 4-5, Table 4-6.
Table 4-4. J3 (J1) connector of TPB (WLB)
Pin#
Signal Name Description
1-6, 8, 10, 12, 14, 16, 18, 20-26
SHIELDShield Driver. These pins are connected to a shield plate to
cancel fringing fields.
7, 9, 11, 13, 15, 17
Electrode 9,....., Electrode 1
Electrode Connections. These are the electrode terminals.
Table 4-5. J4 (J2) connector of TPB (WLB)
Pin#
Signal Name Description
1 SCLK Serial Clock. SPI control clock input pin.
3 MOSI SPI Slave In. SPI control data input pin from MCU to 33993
5 CSBChip Select. SPI control chip selects the input pin from MCU to 33993. Logic 0 allows data to be transferred in.
7 PTA3Direction pin. Determines direction of the DC motor.
(MCU -> H-Bridge)
9 PTB6/TCH2PWM signal pin. Determines speed of the DC motor.
(MCU -> H-Bridge)
11, 13 +5V +5.0V DC power supply
15, 17, 19, 21, 23, 25
+12V +12.0V DC power supply
2, 4, 6, 8, 10, 12, 14, 16, 18, 20,
22, 24, 26GND Ground
Table 4-6. J2 connector of TPB (DB9 female)
Pin#
Signal Name Description
2 TXD Transmit SCI Data
3 RXD Receive SCI Data
5 GND Ground
1, 4, 6, 7, 8, 9 NC Not connected
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 23
Chapter 5 Software
5.1 Contents
5.2 Software Design Consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.3 Main Data Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.4 Firmware Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355.6 FreeMASTER Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.2 Software Design Consideration
Electrode value reading is done by the MCU, by selecting the appropriate channel lines (Table 4-1) and then reading the value on the MCU A/D module. Differences from calibrated values represent changes in the electrode field, meaning the electrode might have been influenced by human touch or water level presence.
The application gives feedback to the user through the on board display, LEDs and a buzzer. The board can also be connected to the PC via an SCI port. On board Display and LEDs are managed using an MSDI device (4.4.6). SCI communication is handled by the implemented FreeMASTER Software.
5.3 Main Data Flow Chart
The general software diagram incorporates the main routine (Main) entered from reset and the interrupt service routines. The general overview of the control algorithm is described in Figure 5-1.
The main routine initializes the MCU, MSDI device and the FreeMASTER software, starts the TIM counter, enable interrupts, performs a delay to let things settle, reads the calibration values, tests the Buzzer and then it enters an endless loop. The endless loop contains four working modules (Touch pad, Slider, Water Pump, Water Slider). The Mode key is tested in every cycle and according to its state, the working modes are switched inside the infinite loop.
Working modes are described in flow charts from Figure 5-3 to Figure 5-6.
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Main Data Flow Chart
Figure 5-1. State Diagram - General Overview
The SCI interrupt services the FreeMASTER communications between the PC and MCU. The Timer Overflow interrupt handles the time delay for the Buzzer (refer to page 35).
Reset
Initialization
Main loopE-Field service
SCI interrupt
done
done
FreeMASTER
Timer Overflow interrupt
INTERRUPTS
Handle delay for Buzzer
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Freescale Semiconductor 25
Main Data Flow Chart
Figure 5-2. Main Data Flow Chart
RESET
Initialization
Start TIM counterTSTOP bit = 0
FreeMASTER initialization
Enable Interrupts
300ms delaydisplay show (0-F)
turn off LED Bar 1000ms delay
Read and store calibration electrode values
Buzzer test
Touch Pad modeSlider mode
Water Pump modeWater Slider mode
Touch Pad mode
mode key pressed
Slider mode
yes
no
mode key pressed no
yes
Water Pump mode
mode key pressed no
yes
Water Pump mode
mode key pressed no
yes
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Main Data Flow Chart
Figure 5-3. Touch Pad Mode Flow Chart
Touch Pad Mode
Delete 7 segment display
Turn on Touch pad LED
mode key pressedyes
Read electrode values
no
Turn on Buzzer for 10mS
Read delta values
Switch to Slider ModeFind the three highest
Autocalibration
Check pressed key
Display pressed keyShow maximum delta value
delta values
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Main Data Flow Chart
Figure 5-4. Slider Mode Flow Chart
Slider Mode
Delete 7 segment display
Turn on Slider LED
mode key pressedyes
Read electrode values
no
Turn on Buzzer for 10mS
Read delta values
Switch to Water Pump ModeFind the three highest
Autocalibration
Detect slider touch and display finger position on the
LED Bar
delta values
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Main Data Flow Chart
Figure 5-5. Water Pump Mode Flow Chart
Water Pump Mode
Delete 7 segment displayTurn on Water Pump LED
mode key pressedyes
Read electrode values
noTurn on Buzzer for 10mS
Read delta values
Switch to Water Slider Mode
Find the three highest
Check pressed key
delta_values7 = pump up buttondelta_values8 = pump down button
delta_values7 > PUMP_THRESHOLDno
yesdelta_values0 = highest conductive band
&&delta_values0 <DELTA_MAX
Stop Motoryes
noPump water up
pump up button pressed
delta_values8>
PUMP_THRESHOLD
delta_values7 - delta_values8>
DELTA_NEIGHBOUR
yes
no
Stop Motor
Pump water out
pump down button pressed
Display the actual water level
pump up or pump down
button pressed
on the LED Bar
delta values, Autocalibration
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Main Data Flow Chart
Figure 5-6. Water Slider Mode Flow Chart
Water Slider Mode
Delete 7 segment displayTurn on Water Slider LED
mode key pressedyes
Read electrode values
noTurn on Buzzer for 10mS
Read delta values
Switch to Touch Pad Mode
Find the three highest
required_level > actual_level
no
yes
&&delta_values0 < DELTA_MAX
yes
no
required_level ≠ 100
yes
no
Stop Motor
Pump water out
Display the actual water level
Get required and actual levels
slider touched
required_level < actual_level&&
delta_values4 > MIN_LEVEL
tmp_level > actual_level&&
delta_values0 < DELTA_MAX
Pump water up Pump water up
yes
no
tmp_level < actual_level&&
delta_values4 > MIN_LEVEL
Pump water out
yes
Stop Motor
no
slider position > measured level
delta_values0 - highest conductive banddelta_values4 - lowest conductive band
slider position < measured level
required position > measured level
required position > measured level
delta values, Autocalibration
on the LED Bar
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Firmware Functional Description
5.4 Firmware Functional Description
Table 5-1. Main, Initialization, FreeMASTER Initialization
Table 5-2. Calibrate Electrodes, Read Values, Read Electrode
Table 5-3. Read Delta, Verify Electrodes, Display Data
Module: main.c main.c freemaster_protocol.c
Function: main InitPorts FMSTR_Init
Syntax: void main(void) void InitPorts(void) void FMSTR_Init(void)
Parameters: none none none
Return: none none none
Description:
Initializes MCU, MSDI and FreeMASTER. Gets the calibration values, scans electrodes, and takes appropriate action.
Initializes MCU (oscillator, GPIO, Timer, ADC, SPI, SCI) and external MSDI device.
FreeMASTER driver initialization (initialize communication and start listening for commands).
Module: main.c main.c main.c
Function: CalibrateElectrodes ReadValues ReadElectrode
Syntax: void CalibrateElectrodes(void) void ReadValues(void)void ReadElectrode(unsigned char)
Parameters: none none channel (MC33794 channel)
Return: none none none
Description:
Reads each electrode value (takes 16 samples and averages the result) and stores it in the electrode’s calibration register.
Scans all electrodes from 1 to NUMBER_OF_ELECTRODES using function ReadElectrode().
Reads the selected channel and places the result into RAM.
Module: main.c main.c main.c
Function: ReadDelta VerifyElectrodes DisplayData
Syntax: void ReadDelta(void) void VerifyElectrodes(void) void DisplayData(unsigned char)
Parameters: none none pressed_key (pressed button)
Return: none none none
Description:
Measures the difference between the current electrode value and the calibration value and stores it as the delta value in RAM. Measures the total sum of delta values.
Finds the three highest delta values .
Displays the pressed key on the 7 segment display using MSDI and a beep is generated when a button is pressed.
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Firmware Functional Description
Table 5-4. Bar Graph, Water Bar Graph, Water Slider Graph
Table 5-5. Rotate Up, Rotate Down, Stop Rotate
Table 5-6. Beep On, Beep Off, Auto Calibration
Module: main.c main.c main.c
Function: BarGraph WaterBarGraph WaterSliderGraph
Syntax: void BarGraph(unsigned char)void WaterBarGraph(unsigned int)
void WaterBarGraph(unsigned int)
Parameters: led (maximum delta value)wbar_delta (total sum of delta values)
wslider_delta
Return: none none none
Description:Routine to handle the LED Bar in Touch Pad mode. The maximum delta value is displayed.
Routine to handle the LED Bar in Water Pump mode. Displays wbar_delta.
Routine to handle the LED Bar in Water Slider mode. Displays wslider_delta.
Module: main.c main.c main.c
Function: RotateUp RotateDown StopRotate
Syntax: void RotateUp(void) void RotateDown(unsigned char) void StopRotate(void)
Parameters: none speed none
Return: none none none
Description:
Generates PWM signal for the H-Bridge to drive the DC motor (pumps water into the water tube).
Generates PWM signal for the H-Bridge to drive the DC motor (pumps water out of the water tube).
Stops the DC motor.
Module: main.c main.c main.c
Function: BeepOn BeepOff AutoCalibration
Syntax: void BeepOn(void) void BeepOff(void) void AutoCalibration(void)
Parameters: none none none
Return: none none none
Description: BeepOn - turn on the buzzer (PTB_PTB7 = 1)
BeepOff - turn off the buzzer (PTB_PTB7 = 0)
Tests conditions and calls the CalibrateElectrodes() function when needed.
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32 Freescale Semiconductor
Firmware Functional Description
Table 5-7. SendSPI, SendpSPI, Delay
Table 5-8. GetTick, Beeper, Count
Table 5-9. Slider, Water Slider, Measure Water
Module: communications.c communications.c delay.c
Function: SendSPI SendpSPI Delay
Syntax: void SendSPI(void) void SendpSPI(char *) void Delay(unsigned int)
Parameters: none pbuff delay_count
Return: none none none
Description:Sends out 24 bits contained in the MSDI array to the SPI port.
Pointered version of SendSPI.Function to wait for the desired time.
Module: delay.c delay.c delay.c
Function: GetTick Beeper Count
Syntax: unsigned int GetTick(void) void Beeper(unsigned int) void Count(void)
Parameters: none delay_beep none
Return: ret_val none none
Description:Reads and returns tick as ret_val (tick is incremented on every TIM overflow).
Turns on the Buzzer for the desired time using BeepOn().
Extra display show on the 7 segment display to let things settle at the start.
Module: slider.c slider.c slider.c
Function: Slider WaterSlider MeasureWater
Syntax:void Slider(unsigned int, unsigned int)
unsigned int WaterSlider(unsigned int, unsigned int)
unsigned int MeasureWater(unsigned int)
Parameters: u_val6, u_val7 u_val8, u_val9 u_val_delta
Return: none wdeltaled tmp_measure
Description:
Detects touch via the slider electrodes (E6 and E7), calculates slider value and displays the result on LED Bar.
Detects touch via the water slider electrodes (E8 and E9), calculates and returns the wdeltaled value.
Measures the current level of water and returns that level converted to the water slider range.
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 33
Firmware Functional Description
Table 5-10. Water Level, Verify Key, Verify Mode Key
Module: slider.c verify.c verify.c
Function: WaterLevel VerifyKey VerifyModeKey
Syntax: unsigned int WaterLevel(void) unsigned char VerifyKey(void) unsigned char VerifyModeKey()
Parameters: none none none
Return:delta_values[4] (5th electrode delta value)
key_number[] (index of pressed key)orNO_KEY_PRESSED
MODE_KEY_PRESSEDorNO_KEY_PRESSED
Description:
Reads and returns the value of electrode E5 (lowest band on the water tube). Used for pumping water out of the tube between modes (from Water pump to Water slider, and from Water Slider to Touch pad mode)
Returns the index of a pressed key if detected, otherwise returns 0.
Returns MODE_KEY_PRESSED if mode key is pressed, otherwise returns 0.
Electric-Field Contact-less Sensing System, Rev. 0
34 Freescale Semiconductor
Interrupts
5.5 Interrupts
This application uses a TIM (Timer Interface Module) Overflow Interrupt Figure 5-7. The TOF (TIM Overflow Flag) bit is set when the counter reaches the modulo value programmed in the TIM counter modulo registers.
This interrupt is generated every 160µs. The variable tick, which is used for time delay, is incremented on every TIM Overflow interrupt. Also, the variable beep is tested in this interrupt routine and according to it’s state the Buzzer is turned off or not.
The SCI interrupt service routine is used to provide communication with the PC. It is fully handled by the implemented FreeMASTER sotware.
Figure 5-7. TIM Overflow Interrupt
TIM Overflow Interrupt
clear TOF
tick++
beep ≠ 0 no
return
yes
beep
beep == 0no
Turn off Buzzer
yes
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 35
FreeMASTER Software
5.6 FreeMASTER Software
The FreeMASTER software was designed to provide an application debugging, diagnostic and demonstration tool for the development of algorithms and applications. It runs on a PC connected to the controller board via an RS232 serial cable. A small program resident in the MCU communicates with the FreeMASTER software to parse commands, return status information to the PC, and to process control information from the PC. FreeMASTER software, executing on a PC, uses part of Microsoft Internet Explorer as the user interface.
The baud rate of the SCI communication for this application is 57600 baud.
A detailed description of the FreeMASTER software is provided in the dedicated FreeMASTER for Embedded Applications documentation.
The FreeMASTER software Control Page is illustrated in Figure 5-8.
Figure 5-8. FreeMASTER Software Control Page
Electric-Field Contact-less Sensing System, Rev. 0
36 Freescale Semiconductor
Chapter 6 Application Setup
6.1 Contents
6.2 Setting Up the Demo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376.3 Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.4 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.5 Modes of E-Field Demonstrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.6 Demo System Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416.7 Starting the Demo System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426.8 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.2 Setting Up the Demo
This E-Field Demo consists of two main parts, the Touch Pad Board (TPB) and Water Level Board (WLB) Figure 6-1. The first step is to connect these two PCBs with each other, using connectors J3, J4 on the TPB, and J1, J2 on the WLB.
Figure 6-1. E-Field (Touch Pad Board, Water Level Board)
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 37
Power Supply
Figure 6-2. E-Field demo (TPB connected with WLB)
6.3 Power Supply
A DC power connector is provided on the E-Field Touch Pad Board to connect a power supply (a +12V DC switching power supply is provided with the demo). The central terminal of the power connector is positive and should be connected to +12V DC, and the second terminal should be connected to ground.
The +12V DC power supply is connected with a main outlet power cord.
6.4 Communication
On board firmware allows communication with a PC using the FreeMASTER Graphical User Interface. To use it, connect a serial cable from a communication port on your PC to the DB9 (RS232) connector on the Touch Pad Board. The female end of the cable connects to the PC and the male end to the board. The communication speed is 57600 Baud.
6.5 Modes of E-Field Demonstrator
The E-Field demo can work in four modes: Touch Pad, Slider, Water Pump, Water Slider. This application starts in Touch pad mode after it is turned on. The Mode Selection Button is used to switch the demo to the next mode. The current mode is displayed on the Water Level Board LEDs D1 - D4.
Electric-Field Contact-less Sensing System, Rev. 0
38 Freescale Semiconductor
Modes of E-Field Demonstrator
Figure 6-3. Mode Selection Button
6.5.1 Touch Pad (Keyboard) Mode
This mode senses the nine electrodes arranged on the Touch Pad Board. They work as a standard keypad. After a touch is detected, the pad number will be shown on the seven segment LED display (DIS1), and on the LED Bar (LEDs D5 - D14) you will see the maximum delta value according to the proximity of the finger.
Figure 6-4. Keyboard
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 39
Modes of E-Field Demonstrator
6.5.2 Slider Mode
This mode senses the Slider electrode, which is placed on the Touch Pad Board between the keypad and the mode selection electrode. Moving a finger along the slider, you will see the position of finger on the LED Bar. It is best to move the finger in the center of the slider to correctly activate the electrodes.
Figure 6-5. Slider
6.5.3 Water Pump Mode
In this mode, you pump water from the bottle to the Water Bar on the Water Level Board. To control the water pump, use the two electrodes: Pump Up button and Pump Down button, placed on the keyboard. The level of the water in the column is displayed on the LED Bar and the number of the electrode which is flooded is shown on the display (DIS1).
Touch and hold a finger on the Pump Up (Down) button, and the motor will pump water up (out) to the moment when the Pump Up (Down) button is released. These buttons are active only when you touch them.
If the application is switched to another mode and there is still some amount of water in the Water Bar, the water is pumped out and then, the mode changes.
Figure 6-6. Pump Up (Down) Button
Electric-Field Contact-less Sensing System, Rev. 0
40 Freescale Semiconductor
Demo System Setup
6.5.4 Water Slider Mode
Moving the finger along the Water Slider, water will be pumped up or out of the Water Bar. The Water Slider is placed on the Water Level Board near to the Water Bar. Water is pumped to the position of the finger on the Water Slider. Even if you release the Water Slider, water will flow to the last required level.
The level of water in the column is displayed on the LED Bar, and the number of electrode flooded is shown on the display (DIS1).
If the application is switched to another mode and there is still some amount of water in the Water Bar, then the water is pumped out and, after that, the mode will change.
Figure 6-7. Water Slider
NOTE: Using modes where the water is pumped, the bottle should be approximately at the same level as the demo application, otherwise the pump is not able to pump the water.
6.6 Demo System Setup
The following actions and cabling must be completed before the E-Field Demonstrator is started:
• connect the Touch Pad Board (connectors J3, J4) and the Water Level Board (connectors J1, J2)
• fill the plastic bottle with water and put one end of the water pump hose into the bottle
• connect the E-Field demonstrator with a serial cable to the host PC using the DB9 modem connector on the Touch Pad Board
• connect the +12V DC power supply to the power connector on the Touch Pad Board
• turn the demo on by switch SW1 (the application starts with a display show from 0 to F, then starts a calibration of the electrodes)
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 41
Starting the Demo System
NOTE: Do not touch electrodes during the calibration. The E-Field demonstrator is ready after the first beep.
This demo has an implemented autocalibration function. Where the buzzer makes a beep with no touching of the demo, it means that the electrodes were calibrated.
The completed demo is shown in Figure 6-2.
6.7 Starting the Demo System
In order to run FreeMASTER on your computer, run the installation file ”fmaster12-38.exe” from the FreeMASTER/freemaster_install directory on the enclosed CD.
Once you have installed the FreeMASTER software, finished the cabling and connected the power supply, turned the demo on with switch SW1, you can start the FreeMASTER program.
6.7.1 Step 1
Start the FreeMASTER program by selecting the Windows menu sequence
Start -> Programs -> FreeMaster 1.2
When the program starts, the screen displays the main application window. If there is no project currently loaded, the window displays a welcome page, as shown in Figure 6-8.
Figure 6-8. Main Window of FreeMASTER Software
Electric-Field Contact-less Sensing System, Rev. 0
42 Freescale Semiconductor
Starting the Demo System
The application window consists of three panes: Project Tree, Detail View and Variable Watch.
The Project Tree pane contains a logical tree structure of the application being monitored/controlled. Users can add project sub-blocks, Scope, and Recorder definitions to the project block, in a logical structure, to form a Project Tree. This pane provides a point-and-click selection of defined Project Tree elements.
The Detail View pane dynamically changes its contents depending on an item selected in the Project Tree. You can find detailed information about this pane in the FreeMASTER Software User Manual.
The Variable Watch pane contains a list of variables assigned to the watch. It displays the current variable values and allows you to change them (if enabled in the variable definition).
All the information related to one application is stored in a single project file with the extension ".pmp".
6.7.2 Step 2
Setup the communication for RS232.
If you are running the FreeMASTER software for the first time, you must setup the communication port and communication speed for the PC. The speed of the demo must be set to 57600 bauds.
Open the Options window by selecting the FreeMASTER software menu sequence:
Project -> Options
Select the appropriate COMx port and set up the speed to 57600 baud. See Figure 6-9.
Figure 6-9. Options Window
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 43
Starting the Demo System
6.7.3 Step 3
Open the FreeMASTER software project from the enclosed CD.
You can open a project by selecting the FreeMASTER software menu sequence:
File -> Open Project -> E-Field.pmp
See Figure 6-10.
Figure 6-10. Open Project Window
If the project opened successfully, new information will be displayed on the screen. See Figure 5-8. The system works as follows: The FreeMASTER software communicates with the embedded application via a well-defined communication protocol. This protocol allows the PC application to issue commands and to read or modify the embedded application variables. All commands and variables used in the FreeMASTER software project must be specified within the project.
Electric-Field Contact-less Sensing System, Rev. 0
44 Freescale Semiconductor
References
6.8 References
1. MC908QB8 data sheet
2. MC33794 data sheet
3. MC33993 data sheet
4. MC33886 data sheet
5. KIT33794DWBEVM - E-Field Imaging Device Evaluation Kit
6. Freescale Reference Manual - Touch Panel System Using the MC33794 E-Field Sensor
7. Freescale AN1985 - Touch Panel Applications Using MC34940/MC33794 E-Field ICs
8. Freescale AN2295 - Developer’s Serial Bootloader for M68HC08 and HCS08 MCUs
9. Freescale AN2395 - PC Master Software Usage
10. Freescale AN2471 - PC Master Software Communication Protocol Specification
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor 45
Appendix A Electric-Field Contact-less Sensing System Schematics
Electric-Field Contact-less Sensing System, Rev. 0
A1 Freescale Semiconductor
Freescale S
emiconductor
A2
LEVELADC3
SCKMOSICSBPTA3PTB6
LEVEL AMP
+12V
+5V
A1A0
+12V
+5V
J4
HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
J4
HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
1 23 4
657 89 10
11 1213 1415 1617 1819 2021 2223 2425 26
JP2
HEADER 3
JP2
HEADER 3
123
Electric-F
ield C
on
tact-less Sen
sing
System
, Rev. 0
Figure A-1. Schematics “A” of Touch Pad Board
R1OUTT1IN
ADC3
PTB6
PTA3
SCKMOSI
CSBR1OUTT1IN
PTB7
PTB7+5V
+5V
+5V
GNDA
GNDA
GNDA
GNDAGNDA
+12V
PTPT
PTA4PTA5
+12V
LEVEL
OFFSET Adjustment
GAIN Adjustment
+
R910KR910K
J2
CON/CANNON9
J2
CON/CANNON9
594837261
C28 4.7uFC28 4.7uF
C24 100nFC24 100nF
Q1MMBF170Q1MMBF170
C23 100nFC23 100nF
R131MR131M
C2710nFC2710nF
U1
MC68HC908QB8DW
U1
MC68HC908QB8DW
Vdd1
PTB7/TCH32
PTB6/TCH23
PTA5/OSC1/AD3/KBI54
PTA4/OSC2/AD2/KBI45
PTB5/Tx/AD96
PTA3/RST/KBI38PTB4/Rx/AD87
PTA2/IRQ/KBI2/TCLK 9PTB3/SS/AD7 10
PTB2/MISO/AD6 11PTA1/AD1/TCH1/KBI1 12PTA0/AD0/TCH0/KBI0 13
PTB1/MOSI/AD5 14PTB0/SCK/AD4 15
Vss 16
+
-
U4-1
LM358
+
-
U4-1
LM358
3
21
84 D2
BZV55C5V1D2BZV55C5V1
+
-
U4-2
LM358
+
-
U4-2
LM358
5
67
R710KR710K
C20 10nFC20 10nF
R3120R3120
R11100KR11100K
1 3
2
C22 100nFC22 100nF
R52.2KR52.2K
U3
MAX202CSE
U3
MAX202CSE
C1+1
V+2
C1-3
C2+4
Vcc 16
T1OUT 14GND 15
R1In 13
C2-5
V-6
T2OUT7
R2IN8
R1OUT 12
T1IN 11
T2IN 10
R2OUT 9
C25 100nFC25 100nF
R1010KR1010K
R810KR810K
R6680R6680
C26
100nF
C26
100nF
R12100KR12100K
13
2
R42.2KR42.2K
BZ1
Buzzer
BZ1
Buzzer
C211uFC211uF
A3
Freescale S
emiconductor
SHIELDSHIELD
1
E3E3
1
SliderSlider
1 2
E4E4
1
E1E1
1
E8E8
1
J3HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
J3HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
1 23 4
657 89 10
11 1213 1415 1617 1819 2021 2223 2425 26
E9E9
1
REF_AREF_A
1
E6E6
1
E7E7
1
E5E5
1
E2E2
1
Electric-F
ield C
on
tact-less Sen
sing
System
, Rev. 0
Figure A-2. Schematic “B“ of Touch Pad Board
+5V
+5V
GNDA
GNDAGND
+12V
PTA0PTA1PTA4PTA5
+12V +5V
LEVEL
OFF
ON
U2
MC33794DWB
U2
MC33794DWB
RST1WD_IN2
NC13
NC25
LAMP_GND4
LAMP_OUT6
NC37
LAMP_SENSE8LAMP_MON9
DIS_SHIELD10
D11C12B13A14
SIGNAL15
LEVEL16
PWR_MON17
LP_CAP18
R_OSC19
NC420 NC5 21NC6 22NC7 23
CLK 24
VDD_MON 25VDD 26VPWR27
VCC 28
AGND29
SHIELD 30
NC8 31
GND32
NC9 33NC10 34
TEST35
E1 36
E2 37
E3 38
E4 39
E5 40
E6 41
E7 42
E8 43
E9 44
REF_A 45
REF_B 46
ISO_OUT 47
NC11 48NC12 49NC13 50
ISO_IN 51
NC14 52
ISO-9141 53LAMP_CTRL54
R147KR147K
R239KR239K
C71nFC71nF
C410nFC410nF
JP1
HEADER 3
JP1
HEADER 3
123
C17 10nFC17 10nF
C18 10nFC18 10nF
C210nFC210nF
GC1GROUND CONNECTION
GC1GROUND CONNECTION
C110uFC110uF
C64.7uFC64.7uF
C15 10nFC15 10nF
C14 10nFC14 10nF
C13 10nFC13 10nF
C12 10nFC12 10nF
SW1SwitchSW1
Switch
21
3
D11N4148D11N4148
C11 10nFC11 10nF
C19 56pFC19 56pF
C310nFC310nF
C10 10nFC10 10nFC8
10nFC8
10nF
J1+12V External power supplyJ1+12V External power supply
+V 1
-V1
2
-V23
C9 10nFC9 10nF
C54.7uFC54.7uF
C16 10nFC16 10nF
Freescale S
emiconductor
A4
SCKMOSICSBPTA3PTB6
+12V
+5V
Power ON
J2HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
J2HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
1 23 4
657 89 10
11 1213 1415 1617 1819 2021 2223 2425 26
R1560R1560
.
DIS1
HD-A103
.
DIS1
HD-A103
CA 3CA 8
DP 5G10F9E1D2C4B6A7nFnF
Electric-F
ield C
on
tact-less Sen
sing
System
, Rev. 0
Figure A-3. Schematic of Water Level Board
MOSISCKCSB
PTA3PTB6
D1D2D3D4D14D13D12
D5D6D7D8D9D10D11
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
+12V
+5V
+12V
+5V
+12V
+ C447uF
+ C447uF
C510uFC510uF
D3
RED
D3
RED
D7
RED
D7
RED
U1
MC33993DWB
U1
MC33993DWB
GND1
SI2
SCLK3
CS4
SP05
SP16
SP27
SP38
SG09
SG110
SG211
SG312
SG413
SG514
SG615
VPWR16 WAKE 17SG13 18SG12 19SG11 20SG10 21SG9 22SG8 23SG7 24SP4 25SP5 26SP6 27SP7 28INT 29
AMUX 30VDD 31
SO 32
SliderSlider
12
D5
RED
D5
RED
E3E3
1
C333nFC333nF
D4
RED
D4
RED
E5E5
1
SHIELDSHIELD
1
D9
RED
D9
RED
J1HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
J1HDR 13X2 SHRD.240" HEIGHT.365" OVERALL HEIGHT
1 23 4
657 89 10
11 1213 1415 1617 1819 2021 2223 2425 26
C110C110
U2
MC33886DH
U2
MC33886DH
PGND 9
PGND 10
PGND 11
PGND 12
AGND 1
OUT1 6
OUT1 7
OUT2 14
OUT2 15
V+ 4
V+ 5
V+ 16
FS2
IN13
IN219
DNC8
DNC20
D118
D213
CCP17
D2
RED
D2
RED
E2E2
1
C210nFC210nF
D8
RED
D8
RED
J3
CON/2screws
J3
CON/2screws
12
D12
RED
D12
RED
D10
RED
D10
RED
D6
RED
D6
RED
D11
RED
D11
RED
D13
RED
D13
RED
E4E4
1
E1E1
1
D1
RED
D1
RED
D14
RED
D14
RED
Appendix B Electric-Field Contact-less Sensing System Bill of Material
Touch Pad Board BOM
Reference Part Value Description Mfg. Mfg. Part No.
BZ1 3-16 V/ 6mA Buzzer any acceptable
C19 56 pF/ 50 VSMD Ceramic
Capacitor, 0805any acceptable
C7 1 nF/ 50 VSMD Ceramic
Capacitor, 0805TDK C2012X7R1H102K
C2, C3, C4, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C20, C27
10 nF/ 50 VSMD Ceramic
Capacitor, 0805 TDK C2012X7R1H103K
C22, C23, C24, C25, C26
100 nF/ 25 VSMD Ceramic
Capacitor, 0805TDK C2012X7R1H104K
C21 1 uF/ 16 VSMD Ceramic
Capacitor, 0805TDK C2012X7R1C105K
C5, C6, C28 2.2 uF/ 16 VSMD Ceramic
Capacitor, 0805TDK C2012X7R1C225K
C1 10 uF/ 16 V SMD Ceramic
Capacitor, 1210 TDK C3225X5R1C106M
D1 1N4148SMD Switching Diode,SOD-80C (minimelf)
any acceptable
D2 BZV55C5V15.1 V Zener Diode,
SOD-80C (minimelf)PHILIPS BZV55-C5V1
J1 PWR JackPower Jack type connector 2.1mm
Elekon K375A
J2 DB9/ female, 90°Connector (RS232/
9pin)
J3, J4Boardmount
SocketPCB socket 2x13 way 3M 8526-4500PL
JP1, JP2 1x3 Pin Header
Q1 MMBF170SMD MOSFET
N-channel transistor, SOT23
ONSEMI MMBF170LT1
R1 47K SMD Resistor, 0805 any acceptable
R2 39K SMD Resistor, 0805 any acceptable
R3 120 SMD Resistor, 0805 any acceptable
R4, R5 2.2K SMD Resistor, 0805 any acceptable
R6 680 SMD Resistor, 0805 any acceptable
R7, R8, R9, R10 10K SMD Resistor, 0805 any acceptable
R13 1M SMD Resistor, 0805 any acceptable
Electric-Field Contact-less Sensing System, Rev. 0
B1 Freescale Semiconductor
R11, R12 100KMulti turn cermet
trimmer (64Y)VISHAY/ Spectrol
594-64Y104
SW1 Switch Slide SPDT Top button APEM 25136NAH
U1MC68HC908QB
8DW8 bit Microcontroller FREESCALE MC908QB8CDWE
U2 MC33794 E-Field sensor chip FREESCALE MC33794DWB
U3 MAX202 RS232 chip Maxim-Dallas MAX202CSE
U4 LM358IC Dual OpAmp (surface mount)
ONSEMI LM358D
Water Level Board BOM
Reference Part Value Description Mfg. Mfg. Part No.
C1, C2 10 nF/ 50 VSMD Ceramic
Capacitor, 0805TDK C2012X7R1H103K
C3 33nF/ 50VSMD Ceramic
Capacitor, 0805any acceptable
C4 47uF/ 16VSurface Mount
Electrolytic capacitorany acceptable
C5 10 uF/ 16 VSMD Ceramic
Capacitor, 1210 TDK C3225X5R1C106M
D1 - D14 LED diodeRed SMD LED diode,
0805KINGBRIGHT KP-2012SURC
DIS1 LED displaySingle digit numeric
display (common anode)
KINGBRIGHT SA52-11EWA
J1, J22x13 way Header
Male PCB Mounting Header, 90°
EZK MLW26A
J3 CON/ 2screws 2 pin connector EZK CZM5/ 2
R1 560 SMD Resistor, 0805 any acceptable
U1 MC33993 MSDI Device FREESCALE MC33993DWB
U2 MC33886 H - Bridge FREESCALE MC33886DH
front windshield filling unit - APO 040.01, 12V DC, manufacturer: SEV
Touch Pad Board BOM
Reference Part Value Description Mfg. Mfg. Part No.
Electric-Field Contact-less Sensing System, Rev. 0
Freescale Semiconductor B2
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