Stand alone trip computer / data logger project.

Developer topics relating to hardware that interfaces PCs to ECUs

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Stand alone trip computer / data logger project.

Postby Technics » Wed Sep 13, 2006 4:37 am


I've been working on an SSM protocol based trip computer/data logger based on an Atmel AVR microcontroller. (90S8535 at the moment and a mess of wires on breadboard, but it is talking. Moving to ATMEGA32 or ATMEGA128 shortly.) I have hooked up an LCD display and can read and display data from the ECU when the ignition is on and the engine isn't running but after I start the engine the connection seems to break and I can't seem to re-init. I'm trying this on my MY02 liberty RX. Any ideas as to why the ECU wont respond with the engine running. I suspect that it may be blocking the comms becuase the diagnostic jumper isn't connected?

In the long term I would like to be able to calculate fuel consumption, display stats and perhaps log data to an SD card. Any opinions, suggestions or random guesses would be appreciated at this point.
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Location: Brisneyland, Australia

Postby deLux » Mon Apr 21, 2008 11:13 am

For what car are you building this?
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Postby NSFW » Thu Apr 24, 2008 11:11 pm

That was posted almost 2 years ago. :) He did say he was testing with an 02 Liberty RX though.

In case the OP comes around again:

Is the AVR wired up to the OBD2 port, or are you using a 3rd-party OBD2 cable? I'm guessing it's electrical noise or something like that. I mean, the ECU still speaks SSM after the engine starts, so what else could it be?

You might try porting your code to the PC - abstract the raw I/O stuff away from the SSM stuff, and implement the I/O layer using asm on the AVR and C libraries on the PC - and then test your SSM code using a Tactrix cable or something similar. That should help determine whether the problem is in the software or the hardware.
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Re: Stand alone trip computer / data logger project.

Postby deLux » Fri Nov 27, 2009 7:16 am

I did something like this for my WM5 Smartphone.
It logs like RomRaider (and better)
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