potentiometer LED driver

#!/bin/bash
ADC_PATH=/sys/bus/platform/devices/TI-am335x-adc/iio:device0/

LEDS[0]="61"
LEDS[1]="44"
LEDS[2]="68"
LEDS[3]="67"

# not exactly accurate for better results
MAX_VALUE=4000

prepare_led()
{
  echo "${1}" > "/sys/class/gpio/export";
  echo "out" > "/sys/class/gpio/gpio${1}/direction";
  echo "1" > "/sys/class/gpio/gpio${1}/value";
}

teardown()
{
  echo "${1}" > "/sys/class/gpio/unexport";
}

#Run if ctrl+c is pressed
control_c()
{
  for LED in "${LEDS[@]}" ; do
    teardown ${LED}
  done
  echo -en "leaving";
  exit $?;
}

trap control_c SIGINT

for LED in  ${LEDS[@]} ; do
  prepare_led ${LED}
done

step=$(((2**${#LEDS[@]})-1))
dividor=$((MAX_VALUE/step))
echo $step

echo "reading"
while true; do
  value=$(cat ${ADC_PATH}/in_voltage4_raw)
  #echo $value
  v=$((value/dividor))
  echo v = $v
  for (( i=$((${#LEDS[@]}-1)); i>=0; i-- )) do
    #echo i = $i
    #echo $((2**i))
    if [ $v -ge $((2**i)) ]
    then
      echo "0" > "/sys/class/gpio/gpio${LEDS[${i}]}/value";
      v=$((v-$((2**i))))
      #echo changed v to $v
    else
      echo "1" > "/sys/class/gpio/gpio${LEDS[${i}]}/value";
    fi
  done
  sleep 0.1
done

control_c