Corvette CCM Reverse Engineering Anyone?

[NomakeWan]

Probably not an issue though - it will still unlock without vats, though it sounds like the reman pin is disabling vats.

This would make sense; you wouldn't want VATS getting in the way at a remanufacturing facility, or on the factory floor. VATS is for a car, which a new/reman CCM is not a part of.

I'd go further with my help but I'm about 2 hours away from a generic arduino logger proof-of-concept that I hope will help NomakeWan immensely. Already have a "fast forward to first valid message" routine. New thread upcoming on that one.

This is what I have on that:

0 
10 59 00 00 00 00 97 
n7 
40 57 00 00 69 
n12 
10 59 00 00 00 00 97 
n19 
40 57 00 00 69 
n24 
10 59 00 00 00 00 97 
n31 
40 57 00 00 69 
n36 
10 59 00 00 00 00 97 
n43 
40 57 00 00 69 
n48 
10 59 00 00 00 00 97 
n55 
40 57 00 00 69 
n60 
10 59 00 00 00 00 97 
n67 
40 57 00 00 69 
n72 
10 59 00 00 00 00 97 
n79 
40 57 00 00 69 
n84 
10 59 00 00 00 00 97 
n91 
40 57 00 00 69 
n96 
10 59 00 00 00 00 97 
n103 
40 57 00 00 69 
n108 
10 59 00 00 00 00 97 
n115 
40 57 00 00 69 
n120 
10 59 00 00 00 00 97 
n127 
40 57 00 00 69 
n-124 
0 
10 59 00 00 00 00 97

This is with the micro finding the first valid message via checksum validation. The only issue I have to fix is that my input buffer is a 255 byte ringbuffer and the message pump isn't correctly handling the wraparound from 255 to 0 (yet).

I see what you're doing here. Pretty neat. Yes, the issue I had had on the original EEHack idle logs is that while it would display a gap time, there was never any gap time between actual messages (that is, there was never a gap between $10, $40 and $41 messages, only after those messages). This shows the actual gap timing. Whether n is nanoseconds or microseconds, it appears to average around 9. Very neat.

I apologize for not responding yesterday. Another race day meant I was out of commission. But I'm back so today I'll be experimenting more with the Arduino to see what's going on. To clarify again, when I mentioned that "the Arduino transmission doesn't appear on the line," I wasn't referring to plugging the Arduino TX directly in. That kills the line completely, which is a different problem (as steveo points out, the Arduino TX idling high is killing the line entirely). The problem I was having was that when I connected the TX line to the bus using a transistor array (which is a rough emulation of the CMOS open drain buffer setup GM uses), that transmission never appeared on the bus. EEHack recorded all the $10 and $40 messages without issue, so the line was live, but the transmissions never appeared.

I do not recall if I did idle logging with the Arduino connected via a diode. I did test the ultra-basic circuit (4.7k resistor between RX and bus, IN914A resistor between TX and bus with stripe towards TX) and the CCM still wasn't happy, but I do not recall if I actually did an idle log with EEHack while it was in that configuration. I will do just that today.