I'm working on a home automation project where my Pi will be interfacing several picaxe chips using an UART serial connection.

Even though I've installed Minicom on the Raspberry Pi and disabled the boot messages, the output is still being held high, resulting in garbled text appearing on the terminal on my PC.

Is there any way to have the Pi hold the serial line low until there is an active data transmission? I am using an AXE027 serial cable (uses an ftdi-based chip) to read data from the serial port.

  • 1
    The TX line should be high until the start bit when it will go low. That's what serial links do. If you want to use some other protocol you'll have to bit bang.
    – joan
    Mar 1 '15 at 20:23
  • @joan I did a bit of research and it turns out that the Raspberry Pi might not be using the same RS-232 protocol. Would it be possible to use 'bit banging' to solve this? Mar 1 '15 at 21:25
  • Possibly. What protocol is being used?
    – joan
    Mar 1 '15 at 21:38
  • Bitbandaging on Raspbian doesn't work well, because it is event driven (the timings are out of synch). Even tuning your script will cause unforeseen problems. I have noticed the same problem(Arduino bridge), and just don't use the Pi UART for anything... because its a nightmare.I have not worked out how to use it properly yet. I2C works well.
    – Piotr Kula
    Mar 1 '15 at 21:56
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    @ppumkin I see what you mean about the timings being out of sync. I've successfully got my Picaxe 08m2 to send a test message to the Raspberry Pi, after changing the transmission method from 'Negative' 2400 baud to 'True' 2400 baud. I think I'll look into i2c communication instead. Mar 1 '15 at 22:02

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