blinkvoltage

#!/bin/bash -u           
# Script_name     : blinkvoltage
# Author          : Bert Lindeman
# Description     : Set the left EV3-led according to the battery voltage
# Version         : v1.3
# Date            : 2014-11-04
# Usage           : blinkvoltage [color]
# Notes           : o color is [ none | red | green | amber ]
#                   o very good to add this script to a crontab
#                     so you get warned by a blinking led if power gets low
# Copyright       : 2014 Bert Lindeman
# License         : GPL-3.0+
#
#============================================================================
#
# Changelog        
# Date     By       Description
# 20141104 BL       prepare for release v1.3
# 20140914 BL       Also use the actual voltage to set the blinkling
# 20140826 BL       o Add script header
#                   o try to prevent abmber blinking flipflop red/green
# 20151230 BL       Adapt to image 20151230. New file names for leds.
#
#============================================================================


  side=left # side to use for the blinking 
  
  v0=6000000 # low
  v1=7100000
  v2=7500000
  v3=8000000 # very good

get_delay() {
# purpose: Determine delay_on and delay_off values depending on current voltage

  # make the sum 1000 so a one second interval

  pctOK=$(bc <<< "scale=0; ($voltage * 100) / ${v3}")
  if   [ $pctOK -ge 95 ]; then # 7.6V 
    intens=10
    # dead slow
    delay_on=10
    delay_off=990
  elif [ $pctOK -ge 85 ]; then # 6.8V   
    intens=127
    # 50/50 but a bit faster
    delay_on=250
    delay_off=250    
  elif [ $pctOK -ge 75 ]; then # 6.0V 
    intens=255
    #rapid blink
    delay_on=50
    delay_off=150
  else 
    intens=255
    #rapid blink
    delay_on=20
    delay_off=180
  fi   
  # echo "\$delay_off=$delay_off \$delay_on=$delay_on \$intens=$intens"
}  
# to prevent flipflopping red<-->green set triggers close to eachother  
# not ALWAYS successful. Do not have a way (yet) to ensure
# AMBER leds and not flip=flopping green/red
setAmber() {
      echo timer      > /sys/class/leds/ev3:$side:green:ev3dev/trigger
      echo timer      > /sys/class/leds/ev3:$side:red:ev3dev/trigger
      echo 500        > /sys/class/leds/ev3:$side:green:ev3dev/delay_on
      echo 500        > /sys/class/leds/ev3:$side:red:ev3dev/delay_on
      echo 500        > /sys/class/leds/ev3:$side:green:ev3dev/delay_off
      echo 500        > /sys/class/leds/ev3:$side:red:ev3dev/delay_off
      echo $delay_off > /sys/class/leds/ev3:$side:green:ev3dev/delay_off
      echo $delay_off > /sys/class/leds/ev3:$side:red:ev3dev/delay_off
      echo $delay_on  > /sys/class/leds/ev3:$side:green:ev3dev/delay_on
      echo $delay_on  > /sys/class/leds/ev3:$side:red:ev3dev/delay_on
      echo $intens    > /sys/class/leds/ev3:$side:green:ev3dev/brightness
      echo $intens    > /sys/class/leds/ev3:$side:red:ev3dev/brightness
}

setRed() {
      echo timer      > /sys/class/leds/ev3:$side:red:ev3dev/trigger
      echo $intens    > /sys/class/leds/ev3:$side:red:ev3dev/brightness
      echo $delay_on  > /sys/class/leds/ev3:$side:red:ev3dev/delay_on
      echo $delay_off > /sys/class/leds/ev3:$side:red:ev3dev/delay_off
}

setGrn() {
      echo timer      > /sys/class/leds/ev3:$side:green:ev3dev/trigger
      echo $intens    > /sys/class/leds/ev3:$side:green:ev3dev/brightness
      echo $delay_on  > /sys/class/leds/ev3:$side:green:ev3dev/delay_on
      echo $delay_off > /sys/class/leds/ev3:$side:green:ev3dev/delay_off

}  
    
  # make sure we do have the variables
  trigger=""
  voltage=0

  # reset BOTH red and green leds unless we want amber
  if [ "$#" -lt 1 ]; then
       trigger="none"
  else
    if [ "$#" -ge 1 ]; then
       trigger=$1
       if [ "$#" -ge 2 ]; then
         voltage=$2
       fi
    fi   
  fi

  # first set all left colors OFF
  ledbase="/sys/class/leds/ev3:$side:red:ev3dev"
  echo none > $ledbase/trigger
  echo    0 > $ledbase/brightness
  
  ledbase="/sys/class/leds/ev3:$side:green:ev3dev"
  echo none > $ledbase/trigger
  echo    0 > $ledbase/brightness
 
  if   [ "$trigger" == none     ]; then 
      exit 0 # a good point to leave here leds have been set already
  elif [ "$trigger" == "amber"    ]; then 
      get_delay
      setAmber $delay_on $delay_off
  elif [ "$trigger" == "red"    ]; then 
      get_delay
      setRed $delay_on $delay_off
  elif [ "$trigger" == "green"  ]; then
      get_delay
      setGrn $delay_on $delay_off
  fi    

exit 0