Thread: Raspberry Pi - Virtual Sensors for Car Computers

Originally Posted by ADecker

The 97-04 and some 05 are not CAN Bus ( There is LIMITED CAN Communication for the ABS Module and other random bits like the radio for some odd reason)

I was afraid of that. Looking at this post http://www.grandprixforums.net/threa...pin-out-needed I did not see the Hi/Low for CAN. Looking at thumbnail 2 it had VSS Hi/Low. I was assuming vehicle speed would be a range and that might be a CAN. I have not found a BCM pin out yet, maybe because 97 does not have one! Without probing we don't learn. :-)

Originally Posted by ADecker

they are VPW and the deep level communication is based on J1850-VPW.

Option #1

AE J1850 VPW (Variable Pulse Width at 10.4/41.6 Kpbs, single wire) Pin 2: BUS+ signal Idle bus level is low High signal voltage level: +7V (min/max 6.25 to 8.00) Low signal voltage level: 0V (min/max 0.00 to 1.50) Up to 12 message bytes, excluding frame delimiters Bit Timing; "1" Bit: Signal low for 128uS or high for 64uS "0" Bit: Signal low for 64uS or high for 128uS Start-Of-Frame: Signal high for 200uS

Option #2

ISO 15765 CAN (250kbit/sec or 500kbit/sec) Pin 6: CAN high (CANH) Pin 14: CAN low (CANL) Dominant or active bus state: CANH driven high while CANL driven low Recessive or idle bus state: CANH and CANL signals are not driven CANH signal voltage level: 3.5V (min/max 2.75 to 4.50) CANL signal voltage level: 1.5V (min/max 0.5 to 2.25)

I have not looked at my DLC yet to see what pins are available. Sounds like I going to see option one and not two. :-(
On one hand that is ok because the papers say something about not all CAN are exposed at the DLC. They also said for example the PCM is built from a lot of ECU's in one box. The CAN bus maybe internal. Again :-(

Originally Posted by ADecker

GM and other manufactures have deep level integration abilities and can and will place commands that they do not publicly document for things like documentation or flashing to the PCM.

Hence the reverse engineering. :-)

Originally Posted by ADecker

a better chip to use is the STN1110

Interesting, I may have to digest this a bit. The interesting thing on the MCP2515 is it had a version that is "SPI" standard. The new Raspberry PI kernel has "SPI" integrated into it, and there are python examples already existing. Not sure how much latency would be added by using the "ST" commands. The specs on the processor sound interesting.

Originally Posted by ADecker

Again I ask what are you trying to accomplish?

Just to learn, and hack around. Not sure what I can accomplish yet without knowing what I can do. If I did not ask, I would not have known about the STN1110 option.
Maybe the ultimate goal would be to have a Raspberry PI, touch screen LCD stack, in my 97 GP, that could display/control various functions. Maybe even be able to create a "Ad Hock" wan to phone app to remote control and get sensors reading. I mean that is way, way, way down the path. I have several pieces to go before that. It just feels like they are there if can be strung together. I have a remote start kit that uses relays for the remote start and doors. I could use the PI to control relays if can not be done through existing communications.
This is just learning what can be done.