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Im using MCP25625 which is MCP2515+integrated MCP2551 and trying to send messages in a loop. For some reson I dont see any signal at all on CANH, CANL lines.

  • SPI communication works correctly
  • I use software reset procedure
  • There is clear 20Mhz sinewave from Crystal
  • There is TXCAN signal

At the moment there is nothing at all connected to CANL,CANH, just the probe.

I also tried to run in LOOPBACK mode and it works, but in the NORMAL modethere is nothing coming out.

Seems like transciever is broken? I changed 2 chips already, so it shouldnt be the problem. Any suggestion guys?

Schematics

user2819955
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2 Answers2

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have you considered the modes of operation of the CAN transceiver?

In your schematic, the pins value is not clear.

If you have connected it to the MCU, Please pull it to LOW to select the normal operation mode for the transceiver (it is different configuration then the CAN controller settings, hence might cause some confusion!).

Controlling it by MCU is a good choice as it gives more control to prevent network communication from being blocked, due to a CAN controller which is out of control.

Else, connect it to ground to ensure normal operation mode specifically for the build in transceiver.

I have referred the data-sheet's of MCP25625, MCP2515 and TJA1050 to bring out this conclusion.

TJA1050 has pin-S for selecting high-speed mode and silent mode. Both modes are similar to normal mode and standby mode respectively of the transceiver of MCP25625.

Also, pin-S configuration in TJA1050 is similar to pin-STBY configuration in MCP25625.

  1. 0(LOW) for high-speed/normal mode of TJA1050/MCP25625-Transceiver
  2. 1(HIGH) for silent/standby mode of TJA1050/MCP25625-Transceiver

Hope this helps.

bluelights
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At the moment there is nothing at all connected to CANL,CANH, just the probe.

Hope you have connected the termination resistor? It is on the schematic, but ...

hjoe
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