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Thread: Does Serial.write() return the byte count?

  1. #1
    Junior Member
    Join Date
    Nov 2012

    Does Serial.write() return the byte count?

    If I have:

    uint16_t write_count;

    write_count = Serial.write(Buffer, length);

    I was expecting to have write_count show the number of bytes written. It does not. It's just zero. What should the correct behavior be here?

    (The reference pages shows it returns a byte [the source seems to show it returns a size_t, which I assume is uint32_t but I'm not sure]).

    Also, is there a good intro page into the magic behind the scenes in this Arduino environment? Is there a map file? Can I turn on compile logs, assembly listings and such so I can see what code is actually going into the build?

  2. #2
    Senior Member
    Join Date
    Jan 2013
    San Francisco Bay Area
    This is an old post, but I just ran into this issue. Serial.write always returns zero, even though I see data outputted in the serial monitor.
    If Serial.write() is guaranteed to send all bytes I guess it doesn't matter much. I was concerned though that maybe only a partial # of bytes were sent, and then I'd have to resend the remaining portion.

    Arduino page says it should return # of bytes sent:

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