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TCAN1145-Q1: can't be woken up

Zoey Wu
Expert 6585 points

Part Number: TCAN1145-Q1

Hi team,

my customer is using TCAN1145-Q1.

tcan1145q1 is configured to receive spurious packets after a specified CAN message wake-up causing the SWCFG bit and SW_EN bit to be cleared and then unable to be woken up. How should this case be configured to keep the transceiver free from spurious packets? Thanks!

  • TI__Guru 53535 points

    Hi Zoey,

    When the TCAN1145 receives enough error frames to cause the frame_overflow threshold to be reached, the device will wake into standby mode and clear the SW_EN bit field. At this point the device is considered awake and the MCU should take action to address the error frames that are appearing on the CAN bus. This should include putting the transceiver into normal mode and clearing the frame_overflow interrupt flag. 

    When all system issues have been resolved and it is time to go back into sleep mode, the MCU should configuration configure the transceiver for partial networking and set the SWCFG and SW_EN bits. If the SW_EN bit is not set, the transceiver will wake up to any WUP on the CAN bus (any valid CAN frame). Before going into sleep mode with partial networking enabled, be sure that all device interrupts are cleared. It is recommended to test SW_EN = 1 in the same SPI write as the mode change to avoid the case where a wake event causes an interrupt to be set before the device moves to sleep.

    Let me know if you have any more questions. 

    Regards, 
    Eric Schott 

  • in reply to Eric Schott1
    TI__Expert 6585 points

    I would like to know, how can I configure the transceiver to wake up only for a specific frame and not be affected by an error frame?

  • in reply to Zoey Wu
    TI__Guru 53535 points

    Hi Zoey,

    Unfortunately there is no way to disable to error frame detection of the transceiver while partial networking is active. This is a safety feature to ensure that if there is and issue on the CAN bus and the transceiver is not able to recognise the data on the bus, it will not be stuck unresponsive. The thought is that if there is an issue with the CAN bus, it is better for the node to wake and have the MCU deal with the problem than remain passively in sleep mode and not be able to contribute to any diagnostics. 

    Regards, 
    Eric Schott 

  • in reply to Eric Schott1
    TI__Expert 6585 points

    After the transceiver is configured to wake up with a specific frame, other frames are sent to the transceiver before the specified frame is sent. However, the transceiver cannot be woken up, and the SW_EN and SWCFG are cleared after the transceiver is powered on. Why?
    Also, does ACK error increase FRAME_CNTx?

  • in reply to Zoey Wu
    TI__Guru 53535 points

    Hi Zoey,

    When configured for partial networking, the transceiver will ignore any valid CAN frame that does not match the configured WUF in the partial networking configuration registers. When a POR reset occurs on Vsup, all configuration data is lost and the transceiver will need to be reconfigured by the MCU. If the transceiver is woken by a frame_overflow condition when enough CAN errors have been recognized, the MCU should similarly reconfigure the device of partial networking so that SW_EN and SWCFG are reset before returning to sleep mode. 

    Does any of this sound inconsistent with what is currently being observed in testing? 

    ACK errors do not count towards the frame_overflow counter.

    Regards, 
    Eric Schott 

  • in reply to Eric Schott1
    TI__Expert 6585 points

    Thank you for your answer.
    The behavior of the transceiver you described is consistent with what I observed in my tests. In the previous test, only one node was connected to the CAN bus. After the node sent other frames, a large number of ACK errors would appear on the bus, resulting in that the correct wake-up frame sent could not be correctly recognized by the transceiver. When the ACK error on the bus is eliminated, the transceiver can be woken up by a specific frame.

  • in reply to Zoey Wu
    TI__Guru 53535 points

    Hi Zoey, 

    I'm glad to hear the transceiver is working as expected! Is there some other behavior that you are having trouble with or can we consider this matter closed for now? 

    Regards, 
    Eric Schott 

  • in reply to Eric Schott1
    TI__Expert 6585 points

    Hi Eric,

    Many thanks for your support! No more questions from my side~