Humble HubbleTeam 18

Tim Brown

Abstract

The proposed project is a self-aiming telescope. This telescope will obtain its global position and

the local time via GPS. It will then automatically orient itself to

point at a user selected target (star) using a variety of onboard

sensors.

Background: http://www.nasa.gov/images/content/708180main_hubble_lose_spiral_full_full.jpg

PSSCs• An ability to establish a coordinate system

based on the telescope's absolute global position via a GPS chipset, and relative orientation based on an accelerometer and electronic compass.

• An ability to compensate for combined variations in the Earth's gravitational and magnetic field, and variations in telescope geometry and mounting configurations via electronic user calibration.

PSSCs• An ability to retrieve celestial coordinates and

targets via Bluetooth from an external host.• An ability to automatically move and point the

telescope at the designated target using feedback loops from integrated motor encoders.

• An ability to allow the user to manually override the telescope's target coordinate using an onboard electronic control interface, and to display information regarding headings on an onboard LCD.

Software Design Considerations

• Flexibility in workload• Ability to manage multiple communications

protocols simultaneously• Maintain as much user functionality as

possible while waiting for sensor data• Capable of trig functions (or simulation) for

stellar target calculations

Software Design Decisions

• Completely Interrupt-driven code– Enables each communications interface to

demand attention when it needs it– Allows sensor initialization to take place “in the

background”– Allows the processor to pass into a low-power

“idle” state while not busy• Use look-up tables for trig calclulations

Memory Map• Executable code• Sine lookup tables• LCD character lookup table• Bluetooth message lookup table• Current position, Current Target, Automatic

Target, Manual Target• Button/encoder states.• Message Buffers for each communication protocol

Peripherals Used• I2C x2 – Sensor Breakout, Motor Encoders• UART x2 – Bluetooth, debugging serial port• SPI – GPS chip• PWM x2 – 2 motors• Timers x2 – Timed interrupts

Main Board

Auxiliary Board

7.2V NiMHBattery

V+ (7.2V Unregulated)

Vss (Ground)

Vss (Ground)Vdd (3.3V regulated)Vcc (5.0V regulated)Hold Power OnOn/Off InterruptV+ (7.2V Unregulated)Motor 1 – BrakeMotor 1 – PWMMotor EnableMotor 2 – BrakeMotor 2 – PWM

Header 111 wires

Breakout Board

Gyro, Compass, Accelerometer

SDA SCL

Vdd (3.3V regulated)Vss (Ground)

I2C Port 34 wires

GPS RXGPS TXGPS ON / OFFBluetooth RESETBluetooth CTSBluetooth RTSBluetooth RXDBluetooth TXD

Header 28 wires

VEX 269 MotorIn

tegr

ate

d En

code

rM

odul

e

Pan Assembly

VEX 269 MotorIn

tegr

ate

d En

code

rM

odul

e

Tilt Assembly

SDA SCLVcc (5V regulated)Vss (Ground)

I2C Port 24 wires

Motor 1 Leads

Motor 2Leads

PIC 24FJ64GB106μCICSP

Header

Hold Power OnOn/Off Interrupt

Motor 1 – BrakeMotor 1 – PWMMotor EnableMotor 2 – BrakeMotor 2 – PWM

GPS RXGPS TXGPS ON / OFFBluetooth RESETBluetooth CTSBluetooth RTSBluetooth RXDBluetooth TXD

Header 28 wires

SDA SCL

I2C Port 3

V+ (7.2V Unregulated)

Vss (Ground)

Header 111 wires

Vss (Ground)Vdd (3.3V regulated)Vcc (5.0V regulated)

Hold Power OnOn/Off Interrupt

V+ (7.2V Unregulated)Motor 1 – BrakeMotor 1 – PWM

Motor EnableMotor 2 – BrakeMotor 2 – PWM

GPS RXGPS TX

GPS ON / OFFBluetooth RESET

Bluetooth CTSBluetooth RTS

Bluetooth RXDBluetooth TXD

VoltageTranslator

SerialPort

Reset Button

Manual / Auto Button

RotaryEncoder 1

RotaryEncoder 2

RotaryEncoder 3

SDA SCLVdd (3.3V regulated)Vss (Ground)

Menu Button 1 Menu Button 2

/ 6 IO pins

/ 2 IO pins

PGE1

/3 Pins

SDA SCL

I2C Port 2

PWM Port 1&2

UART 1&2

SDA SCL

Vcc (5V regulated)Vss (Ground)

/ 2 interrupts

8 pin parallel

Shift Register LCD

DataClockShift

4 Pin UART

I2C Port 2

MainBoar

d

Software Design (Main Loop)

Init

Start

Wait for Interrupts (Idle)

End

Stop Interrupt

Shut Down Peripherals (GPS)

Wait 1 Second

Cut power to Voltage Converters

Init

Initialize Registers for Peripherals

Start GPS chip

Initialize LCD

Initialize Sensors

Init Bluetooth

Load Polaris as Target for

Calibration

End Init

Calibrate Interrupt

Move to Polaris

Allow user to correct position

via rotary encoders

Store encoder offsets

End Calibrate

Initialization and Calibration

Auto or Manual

Get Target From Bluetooth

Get Target From Manual

Update Motor speed + direction

Motor Interrupt

End Motor

UI Interrupt

Check Button States

De-bounce

Update Button Positions

Check Encoder States

Update Encoder Positions

End UI

Motors and UI

Communication Peripherals

Data EventInterrupt

Decode Message Type

Process Data

Invoke Appropriate Response

End Data Event

Questions?