GPS & Sensor Telemetry

Formula SAE

Ryan Langley

2104584

HPV Sensor Suite

Thomas Cross

2107294

HPV Super Series

• Human Powered Vehicle

• Multiple riders per vehicle

• Endurance races

• Manual lap timing

Project Aims

• Sensor suite onboard vehicle

• Location, speed and lap times

• Data logging

• Display data to pit crew

Pit Module•Graphical User Interface

•View real-time data

•Log/display lap times

•Data communications

Vehicle Module•GPS + Accelerometer

•Speed display

•Data logging

•Data communications

GUI

Firmware

Hardware

GUI

Firmware

Hardware

RF Module

Reverse Polarity & Overvoltage Protection

Switched-Mode Power Supply (5V)

Linear Regulator(3.3V)

Liquid Crystal Display

Microcontroller

SD Card

Microcontroller

I2CUART

UART I2C SPI

Input Power

GPS Module Accelerometer

RF Module

Reverse Polarity & Overvoltage Protection

Switched-Mode Power Supply (5V)

Linear Regulator(3.3V)

Liquid Crystal Display

Microcontroller

SD Card

Microcontroller

I2CUART

UART I2C SPI

Input Power

GPS Module Accelerometer

Circuit Protection

• Reverse polarity protection

• Overvoltage protection

• Transient suppression

RF Module

Reverse Polarity & Overvoltage Protection

Switched-Mode Power Supply (5V)

Linear Regulator(3.3V)

Liquid Crystal Display

Microcontroller

SD Card

Microcontroller

I2CUART

UART I2C SPI

Input Power

GPS Module Accelerometer

Power Supply

• 3.3V and 5V rails– Linear regulator for each rail – 5V SMPS powering 3.3V linear regulator– SMPS for each rail– 3.3V @ 0.1A– 5V @ 0.9A

  Ploss (W) Efficiency Cost($AU)

2 x Linear 7.17 40.3% $3.30

1 x SMPS1 x Linear

1.42 77.3% $9.41

2 x SMPS 1.21 80% $15.52

RF Module

Reverse Polarity & Overvoltage Protection

Switched-Mode Power Supply (5V)

Linear Regulator(3.3V)

Liquid Crystal Display

Microcontroller

SD Card

Microcontroller

I2CUART

UART I2C SPI

Input Power

GPS Module Accelerometer

Inputs

• GPS Module– Updates at 10Hz– UART - NMEA Data and checksum– 2.5m location accuracy

• Accelerometer– MMA8451Q– 3-Axis– I2C

RF Module

Reverse Polarity & Overvoltage Protection

Switched-Mode Power Supply (5V)

Linear Regulator(3.3V)

Liquid Crystal Display

Microcontroller

SD Card

Microcontroller

I2CUART

UART I2C SPI

Input Power

GPS Module Accelerometer

Outputs

• RF Module - RFD900– UART– 40km LOS

• LCD– I2C– Displays data to rider

• SD Card– SPI– microSD

RF Module

Reverse Polarity & Overvoltage Protection

Switched-Mode Power Supply (5V)

Linear Regulator(3.3V)

Liquid Crystal Display

Microcontroller

SD Card

Microcontroller

I2CUART

UART I2C SPI

Input Power

GPS Module Accelerometer

Microcontroller

• 2 x UART - GPS & RF Module

• 1 x SPI - SD Card (SPI Mode)

• 1 x I2C - Accelerometer, LCD

• PIC18F46K22– 2 x UART, 2 x SPI/I2C– 64KB Program Memory– 64MHz oscillator

AccelerometerSD Card

GPS

Protection Circuitry

5V SMPS

3.3V LinearRegulator

Programming Header

GUI

Firmware

Hardware

GUI

Firmware

Hardware

Formula SAE

• Design & build race car

• Students of all disciplines

• Annual competition

• Flinders’ first year

GPS Telemetry Project

• Basis for sensor addition

• Build car and driver feedback

• Improve performance of team

Firmware Goals

• Configure sensors

• Read in, send and process data

• Log data

• Handle errors

• All in real time – or close to

GPS

• Configure UART peripheral

• Configure GPS module

• Receive NMEA data

• Process & Send data

Configure UART

• 1 start – 8 data – 1 stop – no parity

• 115,200 baud

• Interrupt based

• Ring buffer

TAIL

HEAD

$ G P R M C

Configure UART

GPS

• Configure UART peripheral

• Configure GPS module

• Receive NMEA data

• Process & Send data

Configure GPS Module

• Send only GPRMC and GPGSA– Lat & long– Date & time– Speed, heading– Precision

• Configure baud to 115,200

• Send data at 10 Hz

GPS

• Configure UART peripheral

• Configure GPS module

• Receive NMEA data

• Process & Send data

Receive NMEA Data

$

\n

GPS_msg_flag

N

YY

N

Receive ISR

GPS

• Configure UART peripheral

• Configure GPS module

• Receive NMEA data

• Process & Send data

Process & Send Data

• Pull msg from RX buffer

M C … \n$ G P R 0

N

NY

Y

Accelerometer

• Configure I2C peripheral

• Configure Accelerometer module

• Obtain data

Configure I2C

• 400 kHz speed

• Set as Master device

• Generic code

Accelerometer

• Configure I2C peripheral

• Configure Accelerometer module

• Obtain data

Configure Accelerometer

• Read latest data (not FIFO)

• 8G, 4G, or 2G mode

• 8-bit resolution

Accelerometer

• Configure I2C peripheral

• Configure Accelerometer module

• Obtain data

Obtain data

• Read the values at 10 Hz

• Use ‘get’ functions to access

X, Y, and Z values.

The Main Loop

The Results

The Results

ACC IN

RFD OUT

GPS IN

Data Logging

• Easy to use

• Windows compatible file system

• Different files for GPS and ACC data

SD_Card.hSD_Card.c

Data Logging

SPI.hSPI.c

FatFsFiles

Main Loop

diskio.hdiskio.c

SD_Card.hSD_Card.c

diskio.hdiskio.c

SPI.hSPI.c

FatFsFiles

Main Loop

SD Card

• Provides high-level logging functions– Create/open files– Log ACC data– Log GPS data– Save files

SD_Card.hSD_Card.c

SPI.hSPI.c

FatFsFiles

diskio.hdiskio.c

Main Loop

FatFs

• Generic FAT File System Module

• Designed for embedded systems

• 3rd party open source

• Platform independent

SD_Card.hSD_Card.c

SPI.hSPI.c

FatFsFiles

diskio.hdiskio.c

Main Loop

Disk IO

• Provides low-level disk IO functions– Initialize– Read– Write– Disk Status

SD_Card.hSD_Card.c

SPI.hSPI.c

FatFsFiles

diskio.hdiskio.c

Main Loop

SPI

• Portable SPI peripheral code

• Various initialization options

• Byte transmit, receive and exchange

Logging Result

GUI

Firmware

Hardware

GUI

Firmware

Hardware

Yes

No

Get Message TypeValid Message Header?No

Yes

New Message Received?

Yes

Valid Message?

Extract Message Data

No

Update Lap/Race Timer

10 Hz

Plot GPS Location Display Acceleration

Lap Detected?

Log Lap Time

Yes

Re

se

t

Receiving Data

• Scan until new message is received

• Check for valid header e.g. “$GPRMC…”

• Check for correct length and checksum

• Extract message data– Lat & long– Date & time– Speed, heading

Update GUI

• Update lap/race counter every 0.1s

• Plot most recent GPS location

• Display accelerometer data

• Display heading/speed

Lap Detection

• Check if travel line crosses finish line

• Log lap time and display on graph/table

• Reset lap timer

GUI

Summary

• Designed generic hardware

• Data processing and transmission

• Display real-time data on user interface

• Autonomously log lap times