TMS320F280039C: MCAN configured as DCAN

Yale Li 李耀先 said:

1. What are the functions of the MCAN_DBTP register and the MCAN_NBTP register, and what are the differences?

Classic CAN operates with a single bit-rate for the entire frame. CAN FD has two bit-rates, one for the nominal phase and another for the data phase. See www.ti.com/lit/SPRAD59 for more information.

Yale Li 李耀先 said:

2. The structure MCAN_BitTimingParams parameters in the routine include MCAN_DBTP's and MCAN_NBTP's. Why does MCAN_setBitTime only use the MCAN_NBTP part?

Not sure I understand. MCAN_setBitTime uses "bitTimes" which includes both NBTP and DBTP segments, as you yourself point out.

Yale Li 李耀先 said:

3. Do I only need to configure the MCAN_NBTP register and then use the MCAN_setBitTime() function to configure it?

If you are going to use the MCAN only in classic CAN mode, configuring NBTP alone is sufficient.

Yale Li 李耀先 said:

4. Do I need to configure the two registers MCAN_DBTP and MCAN_NBTP to have the same bit time, for example, both are configured to 500kbps?

From the title of your thread, it appears you want to use the MCAN in classic CAN mode. In this case, configuring NBTP alone is sufficient. It is also possible to use the MCAN module in CAN FD mode but still use the same bit-rate throughout the frame (BRS=0). In this case also, it should be sufficient to configure NBTP.

Yale Li 李耀先 said:

5. If MCAN is configured as a normal CAN, will MCAN_PSR.RFDF be set to 1 after receiving a CAN2.0 message frame?

 I think what you are really asking is what would happen when a CAN FD frame is received by a MCAN module which has been configured for Classic CAN mode. This is not clearly stated in the module spec. I need to try it out.

Thanks Hareesh,

Hareesh Janakiraman said:

Yale Li said:

5. If MCAN is configured as a normal CAN, will MCAN_PSR.RFDF be set to 1 after receiving a CAN2.0 message frame?

 I think what you are really asking is what would happen when a CAN FD frame is received by a MCAN module which has been configured for Classic CAN mode. This is not clearly stated in the module spec. I need to try it out.

Let me clear, the customer want to know if a MCAN module is configured as a classis CAN, what is the behavior after received a classis CAN message. For simple, they want to treat CAN FD module as a classic CAN module.

And the customer has another question:

Using mcan_ex5_mask_filter_receive, change TX/RX to GPIO4/5, disable FD mode, disable Bit rate switching. After changes, the device only can receive once CAN(not CANFD) message, the second interrupt can not be triggered.

And there is the same phenomenon even use mcan_ex8_range_filter_receive.

Hi Yale,

My customer had exact same problem:

Yale Li 李耀先 said:

Using mcan_ex5_mask_filter_receive, change TX/RX to GPIO4/5, disable FD mode, disable Bit rate switching. After changes, the device only can receive once CAN(not CANFD) message, the second interrupt can not be triggered.

except that they make changes on top of ex10.

In case you want to try it, their problem is solved by removing break point in the ISR.

Best regards,

Hang.