CAN-Bus with SN65HVD230D tranceiver Teensy 4.1

[pm1]

Hi,

I want to communicate with automotive sensors via CAN-Bus on the teensy 4.1. I'm using the SN65HVD230D with the FlexCAN_T4 library. Receiving works, sending messages doesn't. As soon as I use the FlexCAN_T4 .write() function receiving no longer works, either. The .write() function has no physical influence on the CAN bus. I measured it per Oscilloscope.
This code is not working. However if I comment out the sendCANtestMessage() function, receiving is working:

#include <FlexCAN_T4.h>

FlexCAN_T4<CAN1, RX_SIZE_256, TX_SIZE_16> can1;

elapsedMillis timer = 0;
void setup() {
  Serial.begin(115200);
  Serial.println("setup start");
  can1.begin();
  can1.setBaudRate(500000);
}

void loop() {
  if (timer > 100) {
    timer = 0;
    sendCANtestMessage();
    Serial.println("Send Test CAN Message");

    CAN_message_t inMsg;
    if (can1.read(inMsg)) {
      Serial.print("CAN1 ");
      Serial.print("MB: ");
      Serial.print(inMsg.mb);
      Serial.print("  ID: 0x");
      Serial.print(inMsg.id, HEX);
      Serial.print("  EXT: ");
      Serial.print(inMsg.flags.extended);
      Serial.print("  LEN: ");
      Serial.print(inMsg.len);
      Serial.print(" DATA: ");
      for (uint8_t i = 0; i < 8; i++) {
        Serial.print(inMsg.buf[i]);
        Serial.print(" ");
      }
      Serial.print("  TS: ");
      Serial.println(inMsg.timestamp);
    }
  }
}

void sendCANtestMessage() {
  CAN_message_t outMsg;
  outMsg.id = 0xFF;
  outMsg.len = 8;
  outMsg.flags.extended = 0;
  for (byte i = 0; i < 8; i++) {
    outMsg.buf[i] = i;  
  }
  can1.write(outMsg);
}

Any ideas why the .write() function is not working here?

 

[PaulS]

When you connect the oscilloscope to pin 22 [CTX1], do you see a signal there?

Paul

 

[pm1]

Yes, on pin23 too.
But CANH and CANL are on steady 2 V.

 

[PaulS]

Do you have another SN65HVD230D transceiver that you can try?

Paul

 

[pm1]

Yes, same result: signals on CTX1 and CRX1 and steady values on CANH and CANL.

 

[skpang]

The code is working.

I would move the read into the main loop and not inside the timer.

Like this:

void loop() {
   CAN_message_t inMsg;
   if (can1.read(inMsg)) {
      Serial.print("CAN1 ");
      Serial.print("MB: ");
      Serial.print(inMsg.mb);
      Serial.print("  ID: 0x");
      Serial.print(inMsg.id, HEX);
      Serial.print("  EXT: ");
      Serial.print(inMsg.flags.extended);
      Serial.print("  LEN: ");
      Serial.print(inMsg.len);
      Serial.print(" DATA: ");
      for (uint8_t i = 0; i < 8; i++) {
        Serial.print(inMsg.buf[i]);
        Serial.print(" ");
      }
      Serial.print("  TS: ");
      Serial.println(inMsg.timestamp);
    }
    
  if (timer > 100) {
    timer = 0;
    sendCANtestMessage();
    Serial.println("Send Test CAN Message");

   
    
  }
}

 

[skpang]

Post a photo of the CTX1 waveform.

 

[pm1]

Yes, reading should be in the main loop, right. But still the same behavior.

 

[skpang]

Check you have two 120R terminator on your network.

One by the SN65HVD230D and another by the sensor end.

 

[pm1]

One 120 Ohm resistor on the SN65HVD230D and one 100 Ohm resistor at the other end because of lack of 120 Ohm resistors. But I will try it with 120 Ohm.

 

[skpang]

Waveform look oK on CTX1.

Post waveform of CAN_L and CAN_H.

 

[pm1]

CANH is the same steady voltage.

 

[skpang]

Could be a fault with the SN65HVD230D or the automotive sensor.

Post a photo of the SN65HVD230D.

 

[pm1]

The automotive steering wheel angle sensor is working correctly. I need to send values to calibrate the sensor. With PCAN-View Software this is working without problems on the same CAN bus with a USB adapter. However this task should be executed by the teensy. Receiving values is working as long as I'm not using the write() function in any part of the code.

 

[skpang]

Assumed you have wired them up correctly.

If you see waveform on CTX and steady state on CAN_H and CAN_L then the SN65HVD230D breakout board most likely to be faulty.

 

[pm1]

Yes, thanks for supporting me. I measured the CTX1 values on the SN65HVD230D CTX pin. I will order new SN65HVD230D breakout boards.