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Sending data form non TX/RX lines

Discussion in 'Electronic Design' started by en2, Jul 23, 2013.

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  1. en2

    en2 Guest

    Ok. i found myself in one strange situation and i have to find fast way
    out. The guy that designed my pcb has used tx/rx lines to communicate
    with one serial device. The problem is that i have to connect one
    additional device to my pcb but i dont have any rx/tx lines left.

    So i was thinking on doing this:

    I can take 2 unused MCU lines connect them to max485 and pass the data
    to max485/USB and then to PC.

    Now, how to define this lines as "serial" and do i need something else
    accept writing some standard serial routines, setting boud rate etc to
    make this work ?

    E.
     
  2. Jasen Betts

    Jasen Betts Guest

    if you want to do that, a software UART is where's your headed,
    you'll need to set an interrupt at some multiple of the baud-rate,
    so you'll need a spare timer for that.
    yes, you have to do everything else else. (search: "software UART" )
     
  3. hamilton

    hamilton Guest

    The MAX485 device requires 3-lines: Txd, RxD, Enable

    http://datasheets.maximintegrated.com/en/ds/MAX1487-MAX491.pdf
    ( see page 7 )

    Unless you use one pin as serial I/O and one pin to control direction.
     
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