This document provides an overview of Gary "Chunky Ks" Briggs' work developing open source tools for logging and simulating On-Board Diagnostics (OBD) data from vehicles. It summarizes his OBDGPSLogger tool, which logs OBD and GPS data on Linux, OSX and other platforms, and his OBDSim tool, which simulates an ELM327-compatible OBD interface and vehicle data for testing purposes without a physical vehicle. It also provides background on the ELM327 chip and OBD protocol used to communicate with vehicles.

1. When the Rubber Hits the Road:
Making Your Computer Talk to Your Car
Gary “Chunky Ks” Briggs
<chunky@icculus.org>

2. Slides Overview
Me
OBDGPSLogger
ELM327 and OBDII
OBDSim
Demo

3. Me
Grew up & Studied in England
Offered job in LA doing random Linux stuff
Which ended up being print drivers for 6 years
Now I work at a research
nonprofit in Santa Monica
Mostly simulation and modeling
Really, this slide is so I have
somewhere to put this pic --->

4. OBDGPSLogger Genesis
Late 2009, I bought a car with an OBDII port
That's mighty tempting
Idealist requirements:
Linux, OSX. Windows maybe
Log data
No GUI. RasberryPi, SheevaPlug...
Log GPS as well as OBDII
Make pretty pictures

5. OBDGPSLogger Now
http://icculus.org/obdgpslogger
“It does exactly what it says on the tin. It logs
OBDII and GPS data on Linux, OSX and
others”
Mostly C, bits of C++
Open Source
Logs to SQLite
Hokey GUI

6. OBDGPSLogger in Google Earth

7. OBDGPSLogger, Still...
Reads only Mode $01 PIDs
Magically just works
Except I haven't patched in support for current gpsd
Google Earth output
There's a live version, too
Simple analysis stuff
Works with my bike...

8. ELM327 and OBDII
Originally invented at Elm Electronics,
http://elmelectronics.com/obdic.html#ELM327
Most of the high-quality manufacturers implement
their own chip firmware
The ELM327 datasheet taught me most of what I
know

9. ELM327 and OBDII, AT commands
Standard text-based serial protocol
I use PuTTY on Windows, screen(1) on Linux
ELM327 commands might look suspiciously
familiar to older members of the audience
ATZ for reset
ATE0/1 to turn echo on or off
Scantool.net have an additional “ST” command
set

10. ELM327 and OBDII, Getting Data
In short:
> 01 0D
41 0D 1F
>
“Show me mode $01, PID $0D” [vehicle speed]
41 => 0x40 | 0x01
0x40 = success, 0x01 = requested mode
0D => requested PID

11. OBDSim Genesis
Got bored of walking out to car with my laptop
Went looking for ELM327 & OBDII simulator
Idealist requirements:
Command-line
OBDGPSLogger log playback
Actually honors ELM327 commands
Multiple ECUs
Multi protocol support

12. OBDSim Now
http://icculus.org/obdgpslogger/obdsim.html
Pluggable data generators
Works with all OBDII tools I've tried
In the same source as OBDGPSLogger
Has way more users than OBDGPSLogger
Native Windows [MSYS] using com0com

13. OBDSim Supported AT commands
ATAT{0,1,2} – Adaptive timing Cvdddd – Calibrate battery voltage
ATD{0,1} – Display data bytes RV – Request battery voltage
ATL{0,1} – Linefeed ATD – Reset defaults
ATH{0,1} – Headers ATDP – Describe protocol
ATS{0,1} – Space separators ATDPN – Describe protocol by number
ATE{0,1} – Command echo ATI – Request device version id
ATSP[A]{0-9,A-C} – Set protocol ATZ – Reset device
ATST{n} – Set timeout ATWS – Warm start reset
@1, @2, @3 – Device identifier stuff EXIT – Exit OBDSim

14. OBDSim Demo
Launch on Linux, use “-c” to attach screen(1):
obdsim -c
ATZ, total reset
ATE{0,1}, ATS{0,1}, ATL{0,1}
As a developer, you'll turn them all off
For keyboard experimenting, turn them all on
ATI, @1, @2 for identifying device
Couple simple data requests [010D vss, 010C rpm]
ATH1, ATSP7 [CAN 29-bit 500], ATSP1 [J1850]

15. That's all, Folks