Using Motion Sensor HC-SR501

Hong Chen

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

Program write in Python.

#!/usr/local/bin/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)

led.setOutputDirection(0)
pir.setInputDirection()

while True:
    value = pir.getValue().rstrip()

    if(value == "1"):
        print datetime.now(),
        print "motion_detected"
        led.setValue(1)
        time.sleep(led_light_up_time)
        led.setValue(0)

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>
    pir.setInputDirection()
  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
    fd.close()
IOError: [Errno 16] Resource busy
root@Omega-6F83:~#

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

Sr. Sibale

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?

Gabriel Ongpauco

@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.

Gabe

Peter Carr

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

Venet

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

echo 1>/sys/class/gpio/unexport

luz

@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.

Venet

@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