I have created a CAN bus project with two ARDUINO UNO R4 minima that are connected to the VP230 (SN65HVD230DR) modules.
The project is fully operational while both UNO modules are powered via USB C.
As soon as I connect the VCC to the 12V power supply, communication between the UNO does not occur.
Serial monitor not show any errors.
As the power supply is disconnected from the 12V communication is restored.
I have tested all the voltages on the PCB. There are no short circuits.
While 12V power supply is connected, the oscillograph on RX and TX shows active data exchange, but the receiving module shows CAN.available() is 0.
Don't you have any tips on what else can I check?
I found a solution to my problem. After connecting the external power supply 12V to the ARDUINO 5V output, I found a 30mv "noise".
On two identical ARDUINO original modules, both the signal shape and amplitude are different.
I added additional electrolytic 100 µF condensers. This gave the effect, CAN bus worked with a slight delay. Then I also connected the capacitors to the 3.3V outputs, since the CAN TTL adapters are powered from 3.3V. As a result, CAN bus began to work normally.!
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