1. Formula SAE Ryan Langley 2104584
GPS & Sensor Telemetry
HPV Sensor Suite
Thomas Cross
Formula SAE
Ryan Langley

2. HPV Super Series Human Powered Vehicle Multiple riders per vehicle
Endurance races
Manual lap timing

3. Project Aims Sensor suite onboard vehicle
Location, speed and lap times
Data logging
Display data to pit crew

4. Vehicle Module
GPS + Accelerometer
Speed display
Data logging
Data communications
Pit Module
Graphical User Interface
View real-time data
Log/display lap times
Data communications

5. Hardware
Firmware
GUI

6. Hardware
Firmware
GUI

7. Reverse Polarity & Overvoltage Protection
Input Power
Reverse Polarity & Overvoltage Protection
Switched-Mode Power Supply (5V)
Linear Regulator
(3.3V)
GPS Module
Accelerometer
UART
I2C
Microcontroller
Microcontroller
UART
I2C
SPI
RF Module
Liquid Crystal Display
SD Card

8. Reverse Polarity & Overvoltage Protection
Input Power
Reverse Polarity & Overvoltage Protection
Switched-Mode Power Supply (5V)
Linear Regulator
(3.3V)
GPS Module
Accelerometer
UART
I2C
Microcontroller
Microcontroller
UART
I2C
SPI
RF Module
Liquid Crystal Display
SD Card

9. Circuit Protection Reverse polarity protection Overvoltage protection
Transient suppression

10. Reverse Polarity & Overvoltage Protection
Input Power
Reverse Polarity & Overvoltage Protection
Switched-Mode Power Supply (5V)
Linear Regulator
(3.3V)
GPS Module
Accelerometer
UART
I2C
Microcontroller
Microcontroller
UART
I2C
SPI
RF Module
Liquid Crystal Display
SD Card

11. Power Supply 3.3V and 5V rails Linear regulator for each rail
5V SMPS powering 3.3V linear regulator
SMPS for each rail
0.1A
5V @ 0.9A
Ploss (W)
Efficiency
Cost($AU)
2 x Linear
7.17
40.3%
$3.30
1 x SMPS
1 x Linear
1.42
77.3%
$9.41
2 x SMPS
1.21
80%
$15.52

12. Reverse Polarity & Overvoltage Protection
Input Power
Reverse Polarity & Overvoltage Protection
Switched-Mode Power Supply (5V)
Linear Regulator
(3.3V)
GPS Module
Accelerometer
UART
I2C
Microcontroller
Microcontroller
UART
I2C
SPI
RF Module
Liquid Crystal Display
SD Card

13. Inputs GPS Module Accelerometer Updates at 10Hz
UART - NMEA Data and checksum
2.5m location accuracy
Accelerometer
MMA8451Q
3-Axis
I2C

14. Reverse Polarity & Overvoltage Protection
Input Power
Reverse Polarity & Overvoltage Protection
Switched-Mode Power Supply (5V)
Linear Regulator
(3.3V)
GPS Module
Accelerometer
UART
I2C
Microcontroller
Microcontroller
UART
I2C
SPI
RF Module
Liquid Crystal Display
SD Card

15. Outputs LCD SD Card RF Module - RFD900 UART 40km LOS I2C
Displays data to rider
SD Card
SPI
microSD

16. Reverse Polarity & Overvoltage Protection
Input Power
Reverse Polarity & Overvoltage Protection
Switched-Mode Power Supply (5V)
Linear Regulator
(3.3V)
GPS Module
Accelerometer
UART
I2C
Microcontroller
Microcontroller
UART
I2C
SPI
RF Module
Liquid Crystal Display
SD Card

17. 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

18. Protection Circuitry
5V SMPS
GPS
Programming Header
3.3V Linear
Regulator
Accelerometer
SD Card

19. Hardware
Firmware
GUI

20. Hardware
Firmware
GUI

21. Formula SAE Design & build race car Students of all disciplines
Annual competition
Flinders’ first year

22. GPS Telemetry Project Basis for sensor addition
Build car and driver feedback
Improve performance of team

23. Firmware Goals Configure sensors Read in, send and process data
Log data
Handle errors
All in real time – or close to

24. GPS Configure UART peripheral Configure GPS module Receive NMEA data
Process & Send data

25. Configure UART 1 start – 8 data – 1 stop – no parity 115,200 baud
Interrupt based
Ring buffer
TAIL
HEAD $ G P R M C

26. Configure UART

27. GPS Configure UART peripheral Configure GPS module Receive NMEA data
Process & Send data

28. 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

29. GPS Configure UART peripheral Configure GPS module Receive NMEA data
Process & Send data

30. Receive NMEA Data $ \n GPS_msg_flag Receive ISR N N Y Y RXIF
Framing error?
Buffer overflow?
‘$’ or ‘\n’
Put in buffer
Exit
Flush buffer
Receive ISR N N Y Y $
GPS_msg_flag \n

31. GPS Configure UART peripheral Configure GPS module Receive NMEA data
Process & Send data

32. Process & Send Data Pull msg from RX buffer N Y Y N $ G P R M C … \n
Pull char from buffer
Is it ‘$’
Place in array
Is it ‘\n’
Place 0 in array
Check Checksum N Y Y N $ G P R M C … \n

33. Accelerometer Configure I2C peripheral Configure Accelerometer module
Obtain data

34. Configure I2C
400 kHz speed
Set as Master device
Generic code

35. Accelerometer Configure I2C peripheral Configure Accelerometer module
Obtain data

36. Configure Accelerometer
Read latest data (not FIFO)
8G, 4G, or 2G mode
8-bit resolution

37. Accelerometer Configure I2C peripheral Configure Accelerometer module
Obtain data

38. Obtain data Read the values at 10 Hz
Use ‘get’ functions to access X, Y, and Z values.

39. The Main Loop

40. The Results

41. The Results
ACC IN
RFD OUT
GPS IN

42. Data Logging Easy to use Windows compatible file system
Different files for GPS and ACC data

43. Data Logging Main Loop SD_Card.h SD_Card.c FatFs Files diskio.h
diskio.c
SPI.h
SPI.c

44. Main Loop
SD_Card.h
SD_Card.c
FatFs
Files
diskio.h
diskio.c
SPI.h
SPI.c

45. SD Card Provides high-level logging functions Create/open files
Log ACC data
Log GPS data
Save files

46. Main Loop
SD_Card.h
SD_Card.c
FatFs
Files
diskio.h
diskio.c
SPI.h
SPI.c

47. FatFs Generic FAT File System Module Designed for embedded systems
3rd party open source
Platform independent

48. Main Loop
SD_Card.h
SD_Card.c
FatFs
Files
diskio.h
diskio.c
SPI.h
SPI.c

49. Disk IO Provides low-level disk IO functions Initialize Read Write
Disk Status

50. Main Loop
SD_Card.h
SD_Card.c
FatFs
Files
diskio.h
diskio.c
SPI.h
SPI.c

51. SPI Portable SPI peripheral code Various initialization options
Byte transmit, receive and exchange

52. Logging Result

53. Hardware
Firmware
GUI

54. Hardware
Firmware
GUI

55. 10 Hz
New Message Received? No
Update Lap/Race Timer
Yes No
Valid Message Header?
Get Message Type
Plot GPS Location
Display Acceleration
Yes
Reset No
Valid Message?
Lap Detected?
Yes
Yes
Extract Message Data
Log Lap Time

56. 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

57. Update GUI Update lap/race counter every 0.1s
Plot most recent GPS location
Display accelerometer data
Display heading/speed

58. Lap Detection Check if travel line crosses finish line
Log lap time and display on graph/table
Reset lap timer

59. GUI

60. Summary Designed generic hardware Data processing and transmission
Display real-time data on user interface
Autonomously log lap times