Vida CEM swapping

jcdillin · Post by **jcdillin** » 09 Mar 2021, 05:18

MaxDenisov wrote: ↑09 Mar 2021, 05:09 @Vtl.
very good.
Well, I just need to patch my hands)
Do i need to make changes to schematics(is it correct)?

That schematic doesn't look right. the 2nd can port on a teensy 4 is Digital 0 and 1

You also need to run a line from the Highspeed CAN L line to digital 2

Post by **vtl** » 09 Mar 2021, 05:54

High-speed transceiver's RX pin to digital pin 2 works as well (plus you don't need a safety zener diode - and I've seen people using quite a barrel, which surely spoils signal's fronts).

MaxDenisov · Post by **MaxDenisov** » 09 Mar 2021, 06:23

Ok, made some corrections:

Post by **vtl** » 09 Mar 2021, 06:31

jcdillin wrote: ↑09 Mar 2021, 04:52 Well that's cool and frustrating at the same time

Did you run it without termination?

I'm using a teensy just like that with 2 external can transceivers, which the setup works great on the bench.

Verifying the process.

1. Attach teensy to ODB port
2. Wait for serial monitor to show text
3. turn key to pos II

Ran with termination.

1. Attach Teensy to OBD
2. Key in pos II
3. Press reset on Teensy

Make sure nothing else run alive on CAN. I, for example, forgot to unplug my volvo-ddd. Lots of cars, especially in Eastern Europe, have an aftermarket alert and start prevention systems installed - they may be interfering with the cracker on CAN-bus.

Post by **vtl** » 09 Mar 2021, 06:37

MaxDenisov wrote: ↑09 Mar 2021, 06:23 Ok, made some corrections:

Yes, more like that. I also put a DC-DC for 12v to 5v from the OBD port, just to make sure everything has enough power. Plus the wiring is thick'ish (CAT 5e) - somebody mentioned he had a problem with the signal integrity using thin wires.

jcdillin · Post by **jcdillin** » 09 Mar 2021, 08:15

OK, so I am making more progress.

So with Digital 2 directly connected to CAN HS L I'm getting all zeros for the responses.

If I connect digital 2 to the RX pin of the transceiver I'm getting fairly reliable results for bytes 0-1 but 3 keeps coming up with random numbers. At least it's getting closer.

Post by **vtl** » 09 Mar 2021, 08:16

Bump up SAMPLES?

MaxDenisov · Post by **MaxDenisov** » 09 Mar 2021, 09:11

vtl wrote: ↑08 Mar 2021, 21:44

can you please send picture from bottom side? it seems that your wiring a bit different from schematics

Post by **vtl** » 09 Mar 2021, 09:25

The wiring is bad here, I connected +5 from DC-DC to +3.3 on Teensy, plus the low-speed CAN has the L/H pair twisted

It was just an illustration that I finally was able to fight back my laziness and solder the cracker for the field test.

You previous scheme is what I have (+ step down DC-DC).

MaxDenisov · Post by **MaxDenisov** » 09 Mar 2021, 09:35

Ok. my next try is ready and will share results in a hour

Vida CEM swapping

Re: Vida CEM swapping