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Null character on SCI

charles saperstein
Expert 1445 points


Using a F28069.  Using 19200, 8 data bits, 1 stop, no parity. Using SCI-B for RS-485 half-duplex. Occasionally we see a null character on the bus. We are not sure if its being transmitted by the host, transmitted by the device, or just noise on the line. Any ideas?

  • 0
    TI__Mastermind 32995 points
    Hi Charles,

    Can you give us some more information?
    What other/how many devices are you using? Are you using interrupts on the F28069? Can you isolate the problem to see what device is sending the NULL character?

    Best Regards,
    sal
  • 0 in reply to Sal Pezzino
    Expert 1445 points

    Looks like it may be a function of the serial to USB converter we are using for the host computer. We use interrupts for the Receiving.

    I also noticed something. We are using FIFO mode. With no traffic, if I disconnect the serial connector I get an interrupt. I think it may be due to a FE. But it looks like I read the whole SCIRXBUF first and it clears the Bit before we read the bit. Also, I may be getting a BRKDT error as well. Need to do some more investigating.