i.MX6UL dev board: no external CAN messages, loopback ok

[cts]

I have an i.MX6UL dev board, booted, set up, all good.

Connecting CAN1H with CAN2H and CAN2L with CAN2L i can cansend/candump my CAN frames just fine, eg. what I send out on one CAN bus I can receive on the other. The connection is just two wires on the CAN connector J1202.

Now I'd like to send real CAN messages from another device to the dev board. Therefore I have set up two Arduino nanos, each equipped with an mcp2515 CAN transceiver. Sending frames from one to the other works just fine.

Sending frames from one Arduino/mcp2515 combo to the dev board does not work, no messages come through.

Serial parameters are set and fixed to 125kbps on all devices. I suspect wrong logic levels as my oscilloscope shows me vastly different levels (ie. in the two-digit millivolt range on the dev board)...

Do I need an external transceiver for the dev board?

Thank you,

 Christian.

[eriksmits]

According to the Schematic you shouldn't need and external transceiver. It's fitted with 2x MC34901WEF transceivers and also a 120ohm termination resistor on each bus. I would recommend trying with a PEAK CAN device or something similar to test with.

Make sure also the GNDs are connected. CAN bus is differential but only has a limited common mode rejection range so it's good to connect the GNDs also.

Can I ask what connector you used to connect to J1201? There is no information on the Mating connector for this and NXP does not seem to seem a cable. I can only see its a WF1250801200 connector from Shenzen Atom but there's no information on the cable mount connector to mate this.

I don't want to have to solder direct to the PCB, although the unfitted common mode chokes do offer good solder pads if I need to do this.

[Pavel]

Check CAN bus connection between your boards. Draw attention on CAN GND between your boards.

See the following pages:

http://canlab.cz/pages/download/CAN-Wiring.pdf

 

http://www.interfacebus.com/Can_Bus_Connector_Pinout.html

 

http://cms-emu-slicetest.web.cern.ch/cms-emu-slicetest/904/Documentation/Manuals/CAN%20Bus%20Interfa...

Have a great day,
Pavel Chubakov

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