GPIO 03-leds

This script controls LEDs connected to the GPIO, however, it uses different approach. Instead of using python library to handle GPIO pins, is uses direct calls from shell. It is written in bash.

How it works:
If the GPIO pin is called for the first time (it's not initialized yet) then it'll be initialized. After that every LED call will toggle it's current state simply by echoing value (0/1) to GPIO pin (e.g. echo "1" > /sys/class/gpio/gpio17/value)

LEDs are connected as presented in post 02-leds.

Example usage:

./03-leds.sh inf 0.01 102910382947385647746583749283019201

-this creates infinite loop with 0.01s sleep time between change of led state. The last number represents string, which is parsed number by number. Each number represents LED from left most (represented by 1) throught 2,3,4,5 etc. to the right most LED (represented by 0).

This script can be later used as wrapper to directly call GPIO by other scripts.  

03-leds.sh:

#!/bin/bash

# LED mapping
#LEDr1 = 22
#LEDr2 = 17
#LEDr3 = 18
#LEDo1 = 23
#LEDo2 = 24
#LEDy1 = 25
#LEDy2 = 10
#LEDg1 = 4
#LEDg2 = 9
#LEDg3 = 11

# map leds to numbers 0..9
LEDArray=(22 11 9 4 10 25 24 23 18 17)

usage(){
cat << EOF
Direct access to Raspberry PI GPIO pins
krisko 2014

USAGE:
 $0 [OPTION]

EXAMPLE:
 $0 help        display this help
 $0             use STDIN
 $0 <NR>        toggle NR LED (NR: 0-9)
 $0 0.2 12345   blink leds 1..5, interval 0.2 sec
 $0 inf 0.3 123 blink leds 1..3, interval 0.3 sec, infite loop

 e.g. double reversed snake
  $0 inf 0.01 102910382947385647746583749283019201
EOF
 exit 0
}

# after receiving exit signal, shut down all leds
cleanup(){
 echo -e "\nINFO: Cleaning up..."
 for LED in ${LEDArray[*]}; do
        # only shutdown if the led was/is initialized
  [ -L /sys/class/gpio/gpio$LED ] && echo 0 > /sys/class/gpio/gpio$LED/value
 done
 exit 0
}

# trap signals and call cleanup
trap cleanup SIGHUP SIGINT SIGTERM

# init led 
initialize(){
 echo $1 > /sys/class/gpio/export
 echo out > /sys/class/gpio/gpio$1/direction
}

# toggle leds state 0/1
toggle(){
 [ $(cat /sys/class/gpio/gpio$1/value) -eq 0 ] && val=1 || val=0
 echo $val > /sys/class/gpio/gpio$1/value 
}

# close STDERR so we wont see error msg from invalid conditions
exec 2>&-

# do the core cycle
iterate(){
 PARAM=$1
 # if true do only one led toggle and exit w/o cleanup (led stays as is was set)
 NOCLEAN=$2
 [ "$PARAM" == "inf" ] && INF=: && continue
 [ ! $NOCLEAN ] && [ -z $TIME ] && TIME=$PARAM && continue
 # defaul RUN is true
 RUN=:
 while $RUN; do
  # do the iteration x-times
  for (( c=0; c<${#PARAM}; c++ )); do
   NUM=${PARAM:$c:1}
   [ $NUM -le 9 ] && {
    [ ! -L /sys/class/gpio/gpio${LEDArray[$NUM]} ] && initialize "${LEDArray[$NUM]}"
    toggle "${LEDArray[$NUM]}"
   } || echo -e "\nERROR: invalid number"
  sleep $TIME
  done
  # if not infinite cycle, set RUN to false (this will end while cycle)
  [ ! $INF ] && RUN="false"
 done
 # if NOCLEAN is true, don't clean, just exit
 [ ! $NOCLEAN ] && cleanup || exit 0
}

# handle parameters specified from cmd line
for PARAM; do
 # call usage if we need help
 [ "$1" == "help" -o "$1" == "--help" ] && usage
 # set only if one NR is specified from cmd line
 [ "$#" -eq 1 ] && [ "$1" -le 9 ] && NOCLEAN=:
 iterate $PARAM $NOCLEAN
done

# if no input was specified, use stdin
echo "INFO: Enter number 0-9 to toggle LEDs state"
while read -n1 NUM; do
 [ $NUM -le 9 ] && {
 [ ! -L /sys/class/gpio/gpio${LEDArray[$NUM]} ] && initialize "${LEDArray[$NUM]}"
 toggle "${LEDArray[$NUM]}"
} || echo -e "\nERROR: invalid number"
done