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TCAN4550-Q1: TCAN4550 with an External Transceiver: Won't work in Test Mode

Part Number: TCAN4550-Q1
Other Parts Discussed in Thread: ISOW1044, TCAN4550

I am trying to get the TCAN4550 on my board working with an external transceiver (ISOW1044).  

To do this I believe I want to configure the TCAN4550 as shown in Figure 8-11 of the data sheet:

The code I am using to implement this is as follows:


TCAN4x5x_Device_Test_Mode_Enum TestValue = TCAN4x5x_Device_ReadTestMode();


void Init_CAN(void)
// Intialize all control registers

The code was taken from the TCAN4550 demo code.  

TCAN4x5x_DEVICE_TEST_MODE_CONTROLLER has a value of 2, and I've confirmed that the test mode is being set to TCAN4x5x_DEVICE_TEST_MODE_CONTROLLER

When using the TCAN4550 in normal mode with the internal transceiver (via a soldered-on test connector), leaving out the TCAN4x5x.. lines of code I've confirmed proper configuration and operation.  

When I execute the TCAN4x5x lines of code with the ISOW1044 I get no CAN operation. 

Is my firmware as given above correct, or am I missing something?

Thanks in advance for any insight.   

  • Hi Andrew,

    I was recently working with test mode in the lab a couple days ago. In order to turn on the CAN controller only mode I simply wrote:


    I did not need to enable or disable the protected registers. Even though that shouldn't cause an issue with your set up but I will have to look into that further.

    First can you explain how you are connecting the CAN controller to the transceiver, what pin on the TCAN4550 are you connecting to what pin on the ISOW1044. Then can you send a scope shot of the GPO1 and GPO2 pin on the TCAN4550. I want to see a scope shot of you sending a CAN message.

    Let's start there.