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Using Motion Sensor HC-SR501

  • I try a project using motion sensor.
    if motion detected, turn on a LED.

    Program write in Python.

    # -*- coding: utf-8 -*-
    import time
    import onionGpio
    from datetime import datetime
    # LED GPIO
    led_pin = 0
    pir_pin = 9
    sleeptime = 100000
    led_light_up_time = 1
    led = onionGpio.OnionGpio(led_pin)
    pir = onionGpio.OnionGpio(pir_pin)
    while True:
        value = pir.getValue().rstrip()
        if(value == "1"):
            print datetime.now(),
            print "motion_detected"

    It seem work well.
    but a problem is when press Ctrl-C to stop running,
    then try run again, some time cause ”Resource busy“ error.

    root@Omega-6F83:~# python motion2.py
    Traceback (most recent call last):
      File "motion2.py", line 17, in <module>
      File "/usr/lib/python2.7/onionGpio.py", line 158, in setInputDirection
        ret         = self._setDirection(_GPIO_INPUT_DIRECTION)
      File "/usr/lib/python2.7/onionGpio.py", line 134, in _setDirection
        status      = self._initGpio()
      File "/usr/lib/python2.7/onionGpio.py", line 46, in _initGpio
    IOError: [Errno 16] Resource busy

    May be onionGpio not release some "Resource" after Ctrl-C.
    How can I fix it?

  • Another amateur here, running in to the same issue.

    For example here https://docs.onion.io/omega2-maker-kit/starter-kit-seven-segment-display.html, running the Python example, stopping it and trying to run again throws IOError.

    Something needs to be freed, but what?

  • @Sr.-Sibale

    The IOError can happen if you Ctrl-C during a GPIO write/update operation before it unexports the GPIO (this is built-in). As mentioned in the tutorial, you can run a shell script like so:

    echo 1 >/sys/class/gpio/unexport
    echo 2 >/sys/class/gpio/unexport
    echo 3 >/sys/class/gpio/unexport
    echo 11 >/sys/class/gpio/unexport
    echo 18 >/sys/class/gpio/unexport
    echo 19 >/sys/class/gpio/unexport
    echo 0 >/sys/class/gpio/unexport

    Replace the pin #s with the GPIOs you want to free up for reuse.


  • What am I missing? I get
    echo 1 >/sys/class/gpio/unexport
    -bash: echo: write error: Invalid argument

  • @Peter-Carr remove the space before and after ">" so:

    echo 1>/sys/class/gpio/unexport

  • @Venet Removing the space converts that line to something completely different (and not working for the purpose)!

    echo 1 >/sys/class/gpio/unexport

    writes a letter 1 into the file /sys/class/gpio/unexport (which frees gpio1 for re-use, and that's what @Gabriel-Ongpauco wanted to show).

    whereas in

    echo 1>/sys/class/gpio/unexport

    the 1> without a space means redirecting standard output (2> would mean redirecting standard error output), and is eqivalent to just

    echo >/sys/class/gpio/unexport

    (because both 1> and > mean redirecting standard output)
    What this does is writing an empty line to /sys/class/gpio/unexport (with no effect regarding gpios at all)

    @Peter-Carr The "write error: Invalid argument" is because gpio1 was not exported in the first place, thus could not be unexported.

  • @luz you are right of course! I was trying for hours to setup arduino-dock (v.1) on my Omega2+ and getting that same error. Mistyped it without the spaces and that error disappeared. As expected arduino-dock still did not work 😃

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