pc1 usb to spi interface - aos products tech datasheets/9016sm01.pdfpc1 usb to spi interface date...

AOS TECHNOLOGY LIMITEDT. +44 (0)1664 567711F. +44 (0)1664 567712E. [email protected]

46 Pate RdMELTON MOWBRAYLE13 0RGUnited KingdomRegistration No. 3266182VAT No. 684 1011 56

INSTRUCTION MANUAL

PC1 USB TO SPI INTERFACE

Date 3/3/09Doc # 9016sm01Revision 2

9016sm01.doc AOS Technology LtdNot to be reproduced without permission of 18

REVISION TABLE

Date Revision Description3/3/09 1 General text changes.11/01/10 2 J3 pin description corrected


LIST OF CONTENTS

INSTRUCTION MANUAL............................................................................ 1PC1 USB TO SPI INTERFACE .................................................................. 1

REVISION TABLE..................................................................................... 2LIST OF CONTENTS ................................................................................. 3LIST OF TABLES...................................................................................... 4LIST OF figures....................................................................................... 41. INTRODUCTION ................................................................................ 51 FUNCTIONAL DESCRIPTION ................................................................ 62 PIN DESCRIPTIONS ........................................................................... 63 CONTROL INTERFACE ........................................................................ 8

3.1 Data Configuration.......................................................................... 93.2 Data Commands............................................................................10

3.2.1 WRITE contents of serial register to RDAC (A0)............................103.2.2 WRITE contents of serial register to RDAC (A1)............................103.2.3 SAVE contents of RDAC (A0) to EEMEM (A0)................................103.2.4 SAVE contents of RDAC (A1) to EEMEM (A1)................................11

4 SOFTWARE CONTROL........................................................................124.1 Users Own Software.......................................................................124.2 Comments on User Interfacing ........................................................12

5 AOS APPLICATION SOFTWARE ...........................................................135.1 Driver and Software Support ...........................................................135.2 Main Program Screen: Single Controller............................................13

5.2.1 Running the single user application for the first time ....................145.2.2 Running the application software................................................145.2.3 First steps in setting up the interface ..........................................155.2.4 Temperature Tab .....................................................................155.2.5 Setup Tab ...............................................................................155.2.6 Limits Tab ...............................................................................165.2.7 File Data Tab ...........................................................................16

5.3 Main Program Screen: Multiple Controller .........................................165.3.1 Running the Multi interface application for the first time................175.3.2 Running the Multi interface application software...........................175.3.3 First steps in setting up the multi interface..................................185.3.4 Using multiple boards ...............................................................18


LIST OF TABLES

Table 1 16 Bit Serial Data Word ............................................................... 9

LIST OF figures

Figure 1 Schematic of USB functional controls ............................................ 6Figure 2. Photograph of the PC1 controller board ........................................ 6Figure 3. Silkscreen of PC1 controller board................................................ 7Figure 4. Schematic of the SPI interface bus connections ............................. 9Figure 5. Main software screen ................................................................13Figure 6. Main software screen-Multi controller ..........................................16

AOS TECHNOLOGY LIMITEDT. +44 (0)1664 567711F. +44 (0)1664 567712E. [email protected]

46 Pate RdMELTON MOWBRAYLE13 0RGUnited KingdomRegistration No. 3266182VAT No. 684 1011 56

1. INTRODUCTION

The PC1 USB interface is a small piggyback-mounted printed circuit board(PCB) which has been designed to enable computer control of the AOSTechnology Ltd PC1 series peltier controllers.

The interface is based around an FTDI supplied DLP2232M dual UART interfacemodule that is configured to run a simple serial peripheral interface (SPI) bus.Connected to this bus in a daisy-chain fashion are four dual channel digitalpotentiometers. The majority of these controllable pots are used as potentialdividers in order to provide suitable control voltages to the PC1 peltiercontroller board. A spare potentiometer is left unassigned and can be used aseither a simple variable resistor or as part of an internal potential dividernetwork.

The temperature setpoint on the PC1 is controlled in the manual version usinga 13 turn miniature pot, this provides about 11bit of voltage resolution acrossthe control scale. The USB interface board uses a combination of three digitalpots in order to provide full 16 bit control of this voltage, a significantimprovement over the manual version. Chip ENABLE functions and the abilityto set the maximum current, both in a positive (cooling) and negative(heating) direction, as well as the maximum voltage that can be applied acrossthe peltier element can also be controlled using this interface.

Once the controller settings have been updated they can then be written/savedto the memory section on each of the digital pot chips. This default memoryvalue is retained even during power down and is the default value loaded whenthe chips are RESET or powered up. The memory retention period is stated at100 years and it can be written to over 100 thousand times.

Since the FTDI module is a dual channel UART, only one of which is utilised bythe SPI interface, connections to the other are provided by a series of on boardsolder pads. This allows the interface to be used to control the PC1 (or inalternative direct control applications) while providing an additional controlinterface. It is not the purpose of this document to explore the potentialapplications or outline the control possibilities of this additional interface anyfurther.


1 FUNCTIONAL DESCRIPTION

The SPI interface board is usually mounted directly below the PC1 series peltiercontroller board and interfaces directly via a series of header pins through thebottom of the PC1 board. Four corner board stand-offs provide additionalmechanical support and a means on mounting the controller to a substrate.

The schematic below indicates the various PC1 controller board functions thatcan be controlled via the SPI interface card.

Figure 1 Schematic of USB functional controls

2 PIN DESCRIPTIONS

Figure 2. Photograph of the PC1 controller board


Figure 3. Silkscreen of PC1 controller board

P6 PWR connector

Pin Description1 +Vcc2 0 volts

P5 TEC connector

Pin Description1 TEC +2 TEC -

P4 Interface connector

Pin Description1 Vcc2 0 volts3 Bufref4 Shutdn


J3 interface Jumper Connection

Pin Description1 Vmax set point voltage from potentiometer2 Vmax set point voltage input to controller3 Iset(+ve) set point voltage from potentiometer4 Iset(+ve) set point voltage input to controller5 Iset(-ve) set point voltage from potentiometer6 Iset(-ve) set point voltage input to controller7 Vsetpoint set point voltage from potentiometer8 Vsetpoint set point voltage input to controller

NB for PC1 standalone use, pins 1-2, 3-4, 5-6, 7-8 are bridgedFor PC1-USB, the pins in this connector MUST NOT BE BRIDGED. The set point voltage

inputs to the controller are provided by the USB board

J4 External control loop connector

Pin Description1 U3 pin12 U3 pin33 U4B pin1

J2 Control input connector

Pin Description1 Therm2 Shutdn3 Imon4 0 volts

3 CONTROL INTERFACE

As mentioned above the control interface consists of an SPI bus controllingfour daisy-chained, dual channel, 8 bit, digital pots. A schematic of the outlinesystem configuration can be seen in the diagram below.


Figure 4. Schematic of the SPI interface bus connections

The digital potentiometers must be addressed using either the SPI mode 0(CPOL=1, CPHA=0) or mode 1 (CPOL=1, CPHA=1) protocols. The LabViewdemonstration software supplied with this interface has been configured tooperate with a mode 0 protocol. Correct mode operation must be ensured forrobust interface operation especially if user based software is required.

3.1 Data Configuration

Data is written to the interface and clocked through all four chips using aneight byte control string. The write sequence is initiated by driving the chipselect pin low and synchronously clocking the data through the chips. Eachchip receiving two byte of information when the chip select line is drivenhigh.

The 16 bit serial data word which is latched into each chip at the end of thewrite sequence is formatted and consists of a control nibble, an addressnibble and a data byte.

Table 1 16 Bit Serial Data Word

While the chips are capable of operating in a number of different modes thebasic requirement of the interface consist of two functions;


• WRITE data to the appropriate RDAC register. Writing data to thisregister will update the digital pot setting. Each chip has two registers,each which must be written to individually.

• SAVE data to the appropriate EEMEM location. Initiating a save commandwill write the data currently held in the RDAC register to thecorresponding EEMEM location. The data held at this location is usedduring power up and reset to configure the digital potentiometers. Eachchip has two EEMEM locations, each which must be saved to individually.

Since it is only possible to write or save to one of digital pots at a time thentwo eight byte control strings must be used in order to fully address all thedigital pots on the interface. While it is possible to write/save to bank 0 onchip4 followed by bank 1 on chip 3 etc it is much easier if one complete bankis written to at a time. The supplied software operates in this manner,either writing or saving to all the bank 0 RDAC/EEMEM registers/locationsfollowed by all the bank1 RDAC/EEMEM registers/locations.

3.2 Data Commands

A full listing of the instruction commands associated with the digital potchips can be found in the AD5232 data sheet1. There are only four separatecommand codes used by this interface to update to the interface (RDAC) andsave it to the chip memory (EEMEM).

3.2.1 WRITE contents of serial register to RDAC (A0)

The Hex command B0XXH is used latch the 8 bit data byte XX into theRDAC register used to control the bank 0 pot position.

3.2.2 WRITE contents of serial register to RDAC (A1)

The Hex command B1XXH is used latch the 8 bit data byte XX into theRDAC register used to control the bank 1 pot position

3.2.3 SAVE contents of RDAC (A0) to EEMEM (A0)

The Hex command 20xxH is used save the RDAC (A0) data into the EEMEM(A0) memory location. N.B. in this case the contents of the lower byte areunimportant and hence ignored.

1 AD5232, Analog Devices, 8-bit Dual Nonvolatile Memory Digital Potentiometer


3.2.4 SAVE contents of RDAC (A1) to EEMEM (A1)

The Hex command 21xxH is used save the RDAC (A1) data into the EEMEM(A1) memory location. N.B. in this case the contents of the lower byte areunimportant and hence ignored.


4 SOFTWARE CONTROL

The heart of the USB to SPI interface module is a third generation USB dualUART module manufactured by DLP Design Inc and supplied by FTDI. FTDIprovides a royal free Virtual Com Port (VCP) driver that makes the peripheralports look like a standard COM port to the PC. Most existing softwareapplications should be able to interface with the Virtual Com Port simply byreconfiguring them to use the new ports created by the driver. Using the VCPdrivers, an application programmer would communicate with the device inexactly the same way as they would a regular PC COCM port – using theWindows API calls or a COM port library.

The FT2232C driver also incorporates the functions defined for the FTDI’s D2XXdrivers, allowing applications programmers to interface software directly to thedevice using a Windows DLL.

While there are a large number of different ways of communicating with thisUSB UART module it is not the purpose of this document to act as an all-encompassing software reference manual. In addition to the VCP and D2XXdrivers FTDI provide a series of LabView Vis that can be used to access all thefunctions of this module.

The software control applications provided with this interface use acombination of the more general FT_ series Vis and the more specific SPI_ Vis.Both series of drivers are provided on the CD.

4.1 Users Own Software

The FTDI website contains all the driver information and documentationrequired to produce a custom user interface. In addition the support pagesprovide information about using the DLL driver with C++.

4.2 Comments on User Interfacing

Although it is relatively simple process to write a custom user interfaceutilising the supplied resources it is important that the data sent across theinterface is correctly configured. Examination of the chip select, clock anddata line on a storage scope will provide a quick insight into the correctoperation of the interface. Given that the transfer speed across the interfacecan be significant it may be prudent to slow the clock rate in order to viewthe data successfully.


5 AOS APPLICATION SOFTWARE

The AOS application software consists of a built LabView application with itsown installer. Instruction for installing the software can be found in document9016sw01 provided in the attached CD.

5.1 Driver and Software Support

The D2XX driver used in the development of the LabView application Vis willsupport the following operating systems. The version used in thisdevelopment is version 2.04.06 available on the Drivers page of the FTDIwebsite.

• Windows Vista• Windows Vista x64• Windows XP• Windows XP x64• Windows 2000

5.2 Main Program Screen: Single Controller

Figure 5. Main software screen


This application is designed to control a single SPI interface moduleconnected to an AOS PC1 controller. If more than one SPI interface moduleis connected to the control PC then this is indicated in the announcementwindow of the application while the serial number of interface under controlis indicated below this, FT04CDDWA, in the above figure.

This application control interface consists of a number announcementwindows, control buttons and setup tabs.

5.2.1 Running the single user application for the first time

Although the SPI interface controller board is supplied with the TECcurrent and voltage limits set to zero, the control setpoint voltage set toits mid position and the controller disabled it is a good idea to confirmthese setting before connecting the interface to the PC1 controller board.This can be accomplished by leaving the TEC and thermistor unconnectedwhile running the application program. Details about the applicationcontrols can be found in the next section.

5.2.2 Running the application software

To start the controller and control application do the following;

• Connect the PC1 and USB interface boards together• Connect all appropriate connections to the PC1 board, PWR, TEC

connections and thermistor connections.• Connect the USB connector to the USB board and the PC ( N.B. the SPI

board obtains power from the PC1 board)• Select the PC1 single controller program from the main program menu.

It will automatically start. (The board will start up without thecontroller enabled as this is the saved state of the USB interface beforedispatch).

If you are unsure or the start up conditions are unknown it would be wiseto disable the controller manually by shorting pin 2 to pin 4 on the J2control input and then setting and updating/saving suitable limits settingsto the SPI board before removing the shorting pin and using theapplication.

The main screen consists of a number of control buttons placed verticallyalong the left hand side of the screen and some setup tabs that containthe setup data for the controller.

The Control buttons have the following function;


RESET: sets all control voltages to zero volts and sets the wiper on thespare potentiometer to one end of the scale.UPDATE: The PC1 USB interface is updated with the current settings(those outlined in the set up tabs). These setting are not held aftersubsequent power up.UPDATE from file: this button updates the PC1 USB interface from datapreviously saved to fileSAVE to file: saves the current setting to file.SAVE to PC1: saves the current settings to the PC1 USB memory. Ifpowered down and then re-energised then the last saved setting will bepresent on the interface.STOP: Stops the application. The previous setting will be held until powerdown. At subsequent power up the previously saved settings (not the lastupdated settings) will be present on the interface.

5.2.3 First steps in setting up the interface

There are a number of controller settings that MUST be implementedbefore turning on the controller in a real application. In order ofimportance these are;

• Set suitable TEC current and voltage limits. Failure to set suitablelimits may result in the controller overdriving the TEC element and thismay lead to component degradation or failure.

• Set suitable thermistor beta or Steinhart-Hart coefficients. Settingsuitable coefficient will enable accurate temperature indication, withinthe specifications of the fitting algorithm.

• Set a suitable temperature setpoint.• Enable or Disable the controller.

5.2.4 Temperature Tab

Settings on this tab allow the user to update the temperature and enablethe controller. N.B. the enable function is a logical OR with any directelectrical connections, the software control will therefore have no effect ifany other electrical connections dictate the pin enable functionality.

5.2.5 Setup Tab

Settings on this tab allow the user to set the thermistor parameters to beused for the temperature sensor. There are two options; Beta parametersand Steinhart Hart parameters. The subtab visible dictate the parametersused.

Typically these parameters can be obtained from the thermistormanufacturer or by experimentation.


5.2.6 Limits Tab

Settings on this tab allow the user to set the maximum voltage andcurrents that can be applied across and through the Peltier element.Settings allow for different current limits in both directions through theelement.

The value of the sense resistor (usually 50 millohms) is set here as is thenominal value of the spare potentiometer. N.B. the absolute value of thespare pot must be confirmed by measurement due to the substantialcomponent value variation. The sense resistor should not be changed asthis reflects the hardware value found on the PC1 controller board.

5.2.7 File Data Tab

This indicates the data saved to file.

5.3 Main Program Screen: Multiple Controller

Figure 6. Main software screen-Multi controller

This application is designed to control multiple SPI interface modulesconnected to AOS PC1 controller boards. The software above has beendesigned to accommodate upto four SPI interface boards at one time.


LabView code has also been provided should the user require the use morethan four interfaces. The software development has been left to the user inthis case.

This application control interface consists of a number announcementwindows, control buttons and setup tabs. Unlike the single controllersoftware detailed in section 5.2 this application does not allow the saving ofdata or its retrieval from data files. However, it is still possible to RESET,UPDATE and SAVE setup information to the control interface.

5.3.1 Running the Multi interface application for the first time

Although the SPI interface controller board is supplied with the TECcurrent and voltage limits set to zero, the control setpoint voltage set toits mid position and the controller disabled it is a good idea to confirmthese setting before connecting the interface to the PC1 controller board.This can be accomplished by leaving the TEC and thermistor unconnectedwhile running the application program. Details about the applicationcontrols can be found in the next section.

5.3.2 Running the Multi interface application software

To start the controller and control application do the following;

• Connect the PC1 and USB interface boards together• Connect all appropriate connections to the PC1 board, PWR, TEC

connections and thermistor connections.• Connect the USB connector to the USB board and the PC ( N.B. the SPI

board obtains power from the PC1 board)• Select the PC1 controller program from the main program menu. It will

automatically start. (The board will start up without the controllerenabled as this is the saved state of the USB interface before dispatch).

If you are unsure or the start up conditions are unknown it would be wiseto disable the controller manually by shorting pin 2 to pin 4 on the J2control input and then setting and updating/saving suitable limits settingsto the SPI board before removing the shorting pin and using theapplication.

The main screen consists of a number of control buttons placed verticallyalong the left hand side of the screen and some setup tabs that containthe setup data for the controller.

The Control buttons have the following function;


RESET: sets all control voltages to zero volts and sets the wiper on thespare potentiometer to one end of the scale.UPDATE: The PC1 USB interface is updated with the current settings(those outlined in the set up tabs). These setting are not held aftersubsequent power up.SAVE to PC1: saves the current settings to the PC1 USB memory. Ifpowered down and then re-energised then the last saved setting will bepresent on the interface.STOP: Stops the application. The previous setting will be held until powerdown. At subsequent power up the previously saved settings (not the lastupdated settings) will be present on the interface.

5.3.3 First steps in setting up the multi interface

There are a number of controller settings that MUST be implementedbefore turning on the controller in a real application. In order ofimportance these are;

• Set suitable TEC current and voltage limits. Failure to set suitablelimits may result in the controller overdriving the TEC element and thismay lead to component degradation or failure.

• Set suitable thermistor beta or Steinhart-Hart coefficients. Settingsuitable coefficient will enable accurate temperature indication, withinthe specifications of the fitting algorithm.

• Set a suitable temperature setpoint.• Enable or Disable the controller.

5.3.4 Using multiple boards

It is sometimes difficult to keep track of which set of control parametersrelate to which controller interface. It is advisable that the interface serialnumbers are noted in some way so that easy identification can beaccomplished.

pc1 usb to spi interface - aos products tech datasheets/9016sm01.pdfpc1 usb to spi interface date...

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