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CC2652P7: Question on UART Baud Rate Automatic Detection in bootloader.

Connor
Intellectual 840 points

Part Number: CC2652P7

Tool/software:

Hi teams,

My customer is using the CC2652P7 with ROM bootloader.

When the host MCU is sending 0x55, CC2652P7 will also reply 0x55 in the same time. Please see the picture below. Is this the correct mechanism?

Thanks.

BR,

Connor.

  • 0
    TI__Guru**** 223077 points

    Hi Connor,

    Here is the ROM Serial Bootloader Interface Application Note for further reference.  It appears that the CC2652P7 ACKs the baud rate detection sequence, does it then respond correctly to Bootloader Commands (ping, get status, etc.)?  If so then the sequence is correct and the ROM Serial Bootloader is active.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    TI__Intellectual 840 points

    Hi Ryan,

    We know CC2652P7 work correctly.

    What we want to know is why CC2652P7 will send the same 0x55, while the host is sending 0x55.

    Could you please give some explanation?

    Thanks.

  • 0 in reply to Connor
    TI__Guru**** 223077 points

    This is not typical behavior for a SimpleLink F2 device's ROM serial bootloader.  Here is a logic analyzer screenshot of the automatic baud rate detection sequence on a LaunchPad.

    From here it can be seen that the CC26X2 TX line (host RX) is not driven by the CC26X2 until several microseconds after the second 0x55 byte.  The customer's oscilloscope images reflect similar behavior, with an unsteady voltage level prior to this point.  The customer's hardware could be at fault for the host TX (CC2652 RX line) passively influencing (i.e. "bleeding into") the CC26X2 TX line until the CC26X2 asserts control.  The customer will need to test several boards and review their RX/TX line design to make sure they are not connecting electrically.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    TI__Intellectual 840 points

    Got it. Thank you so much.