Monitoring GPIOs via resque

[Ircama]

It could be useful to monitor GPIO ports in rescue mode, to verify that the hardware is working before booting the actual operating system.

The following two programs can be easily preconfigured and then pasted to the rescue shell. They monitor GPIO value changes, without modifying any value (but the direction of the configured ports is set to "in").

Single GPIO monitoring (example: GPIO 6):

GPIO=6

echo $GPIO > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio18/direction
old_value=0
while true
do
read value < /sys/class/gpio/gpio$GPIO/value
if [ $value -ne $old_value ];then
old_value=$value
echo "GPIO $GPIO changed to $value"
fi
done

Multiple GPIO monitoring:

# Configuration of the GPIO ports to be monitored
# Original values for ports can be 0 or 1
s=00000000000000000000000000000000

# 00000000001111111111222222222233
# 01234567890123456789012345678901
s=______0_1____0___0_1_0____1_____

# Activation of the GPIO ports that have been set to 0 or to 1
gpio=-1
while true
do
let gpio=gpio+1
old_val="${s:$gpio:1}"
test "$old_val" || break
test "$old_val" == 0 -o "$old_val" == 1 || continue
test -d /sys/class/gpio/gpio$gpio && continue
echo "Activating GPIO $gpio"
echo $gpio > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio$gpio/direction
done

# Monitoring of the GPIO ports that have been set to 0 or to 1
while true
do
gpio=-1
while true
do
let gpio=gpio+1
old_val="${s:$gpio:1}"
test "$old_val" || break
test "$old_val" == 0 -o "$old_val" == 1 || continue
test -d /sys/class/gpio/gpio$gpio || continue
read value < /sys/class/gpio/gpio$gpio/value
if [ $value -ne $old_val ];then
f=${s:$gpio}
s=${s:0:$gpio}$value${f:1}
sp=""
test ${#gpio} == 1 && sp=" "
case $gpio in
2) label="I2C bus 1, SDA";;
3) label="I2C bus 1, SCL";;
4) label="1WIRE";;
14) label="UART0_TXD";;
15) label="UART0_RXD";;
# Additional custom labels can be configured here:
# ...
*) label="";;
esac
echo "GPIO $sp$gpio changed to $value [$s] - $label"
fi
done
done