Signal strength LED meter

Sometimes you may need a simple indicator to know if the link has a good signal strength. Or for moving an antenna to catch the remote AP. Using leds is the more simple aproach.

This script uses 5 different blinks on the same led to show the signal strength. When blinking, if the led is more time on, it means the signal is better.

The image shows left to right worst to best signal.

#!/bin/sh
#Filename: ledwsignal.sh 
#Description: This script shows wifi signal strength by blinking one led.
#2015 raphik, danitool
 
AVLEDS=`ls /sys/class/leds`
ELED=`ls /sys/class/leds|grep -wo -m1 "$1"`
OLD_STRENGTH=-1
 
Led_On() { 
	  echo $2 > /sys/class/leds/$1/delay_on 
}
 
Led_Off() {
	  echo $2 > /sys/class/leds/$1/delay_off
}
 
#HELP
if [ "$#" -ne 1 ] || [ "$ELED" != "$1" ]; then
    printf "\nUSAGE:
    ledwsignal.sh <led name>
    \navailable leds:\n$AVLEDS
    \n\nERROR\n"
    exit 255
fi
 
echo timer > /sys/class/leds/$1/trigger
 
while true ; do
  RSSI=`cat /proc/net/wireless | awk 'NR==3 {print $4}' | sed 's/\.//'`
  #echo "RSSI: $RSSI"
 
  if [ -z $RSSI ] || [ $RSSI -ge 0 ]; then STRENGTH=0 #error
  elif [ $RSSI -ge -65 ] ; then STRENGTH=4 #excellent
  elif [ $RSSI -ge -73 ] ; then STRENGTH=3 #good
  elif [ $RSSI -ge -80 ] ; then STRENGTH=2 #fair
  elif [ $RSSI -ge -94 ] ; then STRENGTH=1 #bad
  else STRENGTH=0
  fi
 
  if [ $OLD_STRENGTH != $STRENGTH ] ; then
    case $STRENGTH in
      4)  Led_On $1 1960; Led_Off $1 40 ;;
      3)  Led_On $1 950;  Led_Off $1 50  ;;
      2)  Led_On $1 500;  Led_Off $1 500 ;;
      1)  Led_On $1 50;   Led_Off $1 950  ;;
      0)  Led_On $1 40;   Led_Off $1 1960 ;;
    esac
    echo "STRENGTH (0-4): $STRENGTH"
  fi
 
OLD_STRENGTH=$STRENGTH
 
sleep 3
done
exit

This script virtually controls the brightness of the led using the concept of PWM for brightness, with an interval of 20 miliseconds and 4 states:

• Excelent signal: Full brightness (no PWM)
• Good signal: High brightness
• Fair signal: Low brightness
• Bad signal: Minimal brightness (1 milisecond on)
• Signal error: Blinking led

#!/bin/sh
#Filename: ledwsignal.sh 
#Description: This script shows wifi signal strength by controlling one led brightness
#2015 raphik, danitool
 
AVLEDS=`ls /sys/class/leds`
ELED=`ls /sys/class/leds|grep -wo -m1 "$1"`
OLD_STRENGTH=-1
 
Led_On() { 
	  echo $2 > /sys/class/leds/$1/delay_on 
}
 
Led_Off() {
	  echo $2 > /sys/class/leds/$1/delay_off
}
 
#HELP
if [ "$#" -ne 1 ] || [ "$ELED" != "$1" ]; then
    printf "\nUSAGE:
    ledwsignal.sh <led name>
    \navailable leds:\n$AVLEDS
    \n\nERROR\n"
    exit 255
fi
 
echo timer > /sys/class/leds/$1/trigger
 
while true ; do
  RSSI=`cat /proc/net/wireless | awk 'NR==3 {print $4}' | sed 's/\.//'`
  #echo "RSSI: $RSSI"
 
  if [ -z $RSSI ] || [ $RSSI -ge 0 ]; then STRENGTH=0 #error
  elif [ $RSSI -ge -65 ] ; then STRENGTH=4 #excellent
  elif [ $RSSI -ge -73 ] ; then STRENGTH=3 #good
  elif [ $RSSI -ge -80 ] ; then STRENGTH=2 #fair
  elif [ $RSSI -ge -94 ] ; then STRENGTH=1 #bad
  else STRENGTH=0
  fi
 
  if [ $OLD_STRENGTH != $STRENGTH ] ; then
      if [ $OLD_STRENGTH = 4 ] ; then echo timer > /sys/class/leds/$1/trigger
      fi
      case $STRENGTH in
	4)  echo default-on > /sys/class/leds/$1/trigger ;;
	3)  Led_On $1 12;  Led_Off $1 8  ;;
	2)  Led_On $1 6;   Led_Off $1 14 ;;
	1)  Led_On $1 1;   Led_Off $1 19  ;;
	0)  Led_On $1 500; Led_Off $1 500 ;;
      esac
  echo "SIGNAL STRENGTH (0-4): $STRENGTH"
  fi
 
OLD_STRENGTH=$STRENGTH
 
sleep 3
done
exit

Note: to appreciate the different led states with this script you may need to be in a dark environment.