powerblock

#!/system/bin/sh

### BEGIN INIT INFO
# Exec: ready
# Process: new
### END INIT INFO

VERSION_NUMBER="1.2.0"

# Common path for all GPIO access
BASE_GPIO_PATH=/sys/class/gpio

# Assign names to GPIO pin numbers
STATUS_PIN=17
SHUTDOWN_PIN=18

# Assign names to states
STATE_ON="1"
STATE_OFF="0"

doRun=$STATE_ON

# Exports a pin if not already exported
# Parameter $1: pin number
exportPin() {
  if [ ! -e "$BASE_GPIO_PATH/gpio$1" ]; then
    echo "$1" > "$BASE_GPIO_PATH/export"
  fi
}

# Set a pin as an output
# Parameter $1: pin number to be set as output pin
setDirectionOutput() {
  echo "out" > "$BASE_GPIO_PATH/gpio$1/direction"
}

# Set a pin as an output
# Parameter $1: pin number to be set as output pin
setDirectionInput() {
  echo "in" > "$BASE_GPIO_PATH/gpio$1/direction"
}

# Set value of a pin
# Parameter $1: pin number
# Parameter $2: output value. Can be 0 or 1
setPinValue() {
  echo "$2" > "$BASE_GPIO_PATH/gpio$1/value"
}

# Returns the current pin value
# Parameter $1: pin number to be read from
getPinValue() {
  cat "$BASE_GPIO_PATH/gpio$1/value"
}

doShutdown() {
  reboot -p  # Android call for shutting down the system
  doRun=$STATE_OFF
}

exportPin "$STATUS_PIN"
exportPin "$SHUTDOWN_PIN"

setDirectionOutput "$STATUS_PIN"
setDirectionInput "$SHUTDOWN_PIN"

setPinValue "$STATUS_PIN" "$STATE_ON"

echo "[PowerBlock] Service started, version $VERSION_NUMBER"
log -p i -t "PowerBlock" "Service started, version $VERSION_NUMBER"

# Poll shutdown signal once per second
while [ "$doRun" -eq "$STATE_ON" ]; do
  sleep 1
  currentValue=$(getPinValue "$SHUTDOWN_PIN")
  if [ "$currentValue" -eq "$STATE_ON" ]; then
    echo "[PowerBlock] Shutdown signal detected."
    log -p i -t "PowerBlock" "Shutdown signal detected."
    doShutdown
  fi
done