Time goes by... fast

It's been about a year since we last updated this blog. It's incredible how much time we need to do things, and how it's difficult to get some. Or maybe it's me aging.
Anyway. After building the "demo" can bus, we were hoping that the process of validation of our scanner should be easier. We were wrong. Not only the scanner doesn't work yet, but we faced some unexpected problems that "the pure theory" has not foreseen. The theory says "if you get a packet, you have found the right speed". Yes... but we get many packets at many different speeds, overflows, wrong packets, bursts incompatible with speed settings.... AAAARGH!!!!
We gave up for some time, but now it's revenge time.
The third PIC (PIC18F4685) is coming, and this will let us have a working bus that we know, with known speed and known packets, and we will build a CANscanner that we can test and tune on it.

The battle has begun!

BZZZAAP!!!

Hi ALL!! After a long, long time we are back! Holidays, work and H1N1 (well... not really, only ordinary flu :-) ) have delayed our serious work, but yesterday we restarted it. As you can see...

some ruffled wires were connected to the EODB port. This is not really the first time that we interface our circuit to the car, but the last try was a failure. After some changes (both in code and wires) we do it again.

Results:

not many, really. We detect correctly the start of trasmission on the bus: when we turn on the ignition switch our circuit start receiving packets. Unfortunately the PIC module signals "overflow" status on CAN receiver, so we haven't received nothing meaningful. We hope we have guessed right the bus transmission speed, but we have to investigate further.

We did some exeriments on receiving packets (echoing on serial port, binking led...) to locate the problem, but the available time runs out quickly. But there will be the second round. :-)

Looking in the photos (sorry about the quality, the pictures are taken with a cellular phone in the dark, so noise is clearly visible) you can see the wires connecting EOBD in the hole above the shift lever and the circuit. The grey cable (a chunk of CAT5) on the right is connected to the serial port of laptop (not shown), you can see it a little better on the above photo. The dark box with leds turned on is PICkit2, the PIC programmer (also connected to laptop). We were doing real-time debugging of firmware :-)

That's all folks! We will be back as soon as possible, to continue this first part of the project. Stay tuned!