OVMS# obdii can1 request device 735 7b5 1003
735[7b5] 1003: Response:
00 32 01 f4                                     | .2..            
I (64032248) webserver: HTTP POST /api/execute
I (64032258) webcommand: HttpCommandStream[0x3f8b5268]: 3499932 bytes free, executing: obdii can1 request device 735 7b5 2701
OVMS# obdii can1 request device 735 7b5 2701
735[7b5] 2701: Response:
3a 07 4e 87                                     | :.N.            

On 25 Oct 2021, at 12:46, Michael Balzer <dexter@expeedo.de> wrote:

Shane,

not sure why you don't use the OBD request command for this instead of manual frame assembly.

However, regarding writes to PIDs:

- You may need another session type. Most cars now won't accept 03 as a session with PID write access, but expect some custom session type to allow that. The NRC 7F means "serviceNotSupportedInActiveSession" (btw: the OBD command translates the most common NRCs for you), which is a hint you need another session.

- You normally don't need tester presence if you send the request shortly after the session init. Most devices will keep a session logged in for at least 60 seconds, custom session types may expire faster. Use a script if in doubt, or start a tester presence signal using the "re obd tester" subcommand.

- I doubt you do, but if (!) you really need security access (request 27), that will normally work differently. See section 9.4 in the ISO document: you need to create a key from the seed given by the server. So you need to know how to calculate the key, which normally involves some non-obvious encryption method. You may be able to derive the method from looking at CAN logs of a service device gaining access.

I would try other session types first.

Hint: you can use a script to walk through a range of session types and try the write after each one.

See: https://docs.openvehicles.com/en/latest/userguide/scripting.html#ovmsvehicle → OvmsVehicle.ObdRequest(arguments)

Be aware that's a synchronous call, so don't let the loop run for longer than 60 seconds to avoid the watchdog.

Regards,
Michael


Am 25.10.21 um 11:06 schrieb Shane @ Kilve Engineering:

Hi all,

Can anyone give me some help trying to write data to the TPMS ecu?

I can read for example FL tyre using
can can1 tx standard 735 03 22 e0 10 00 00 00 00 (FL id e010 FR e020 etc.)
And get back 07 62 e0 10 80 2d b9 d4

I have confirmed that the tyre id is "80 2d b9 d4” with a tmps reader wireless at the wheel

I have then done a session control with
can can1 tx standard 735 02 10 03 00 00 00 00 00
And get back 06 50 03 00 32 01 f4 00
So that looks ok ?

So I then try
can can1 tx standard 735 07 2e e0 10 40 ea 85 ce (the new id)
And get back 03 7f 2e 7f

So ive tried issuing
can can1 tx standard 735 02 27 01 00 00 00 00 00

But get no response??


any pointers?
p.s. do I also need to be sending tester present to the ecu? Or does the fact im doing a session control take care of this?


Regards
Shane
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