Xiaomi Gateway Light

light.sh

#!/bin/bash

# usage:
#
# ./light.sh $RED $GREEN $BLUE $TRANSITION_TIME_MS $STEP_SIZE
#
# colors are 0-100, transition time in milliseconds, step size means how much
# fade can step between color values in each iteration
#
# example:
#
# ./light.sh 12 34 56 2000 1
#

# yes it is swapped
r_addr="/sys/class/backlight/lumi_b/brightness"
g_addr="/sys/class/backlight/lumi_g/brightness"
b_addr="/sys/class/backlight/lumi_r/brightness"

start_r=$(cat "$r_addr")
start_g=$(cat "$g_addr")
start_b=$(cat "$b_addr")

set_color () {
    # because it blinks on 43
    if [ "$1" != 43 ]; then
      echo "$1" > "$r_addr"
    fi
    if [ "$2" != 43 ]; then
      echo "$2" > "$g_addr"
    fi
    if [ "$3" != 43 ]; then
      echo "$3" > "$b_addr"
    fi
}


abs () {
    if [ $1 -lt 0 ]
    then
        echo "$(($1 * -1))"
    else
        echo "$1"
    fi
}

max () {
    local arg max=0
    for arg
    do
        if [ "$arg" -gt "$max" ]
        then
            max=$arg
        fi
    done
    echo "$max"
}

fade () {
    local step=$1 transition=$2
    local start_red=$3 start_green=$4 start_blue=$5
    local end_red=$6 end_green=$7 end_blue=$8
    local delta_red=$(abs $(($end_red - $start_red)) )
    local delta_green=$(abs $(($end_green - $start_green)) )
    local delta_blue=$(abs $(($end_blue - $start_blue)) )
    local i=0
    local max=$(max "$delta_red" "$delta_green" "$delta_blue")

    if [ "$delta_red" = 0 ] && [ "$delta_green" = 0 ] && [ "$delta_blue" = 0 ]
    then
        return
    fi

    if [ "$step" -lt 1 ]
    then
        step=1
    fi

    local sleep=$(echo "scale=3; $transition/$max/1000/1.8" | bc)

    while [ "$i" -le "$max" ]
    do

        red=$(( $start_red + ($end_red - $start_red)  * $i / $max ))
        green=$(( $start_green + ($end_green - $start_green) * $i / $max ))
        blue=$(( $start_blue + ($end_blue - $start_blue) * $i / $max))
        set_color "$red" "$green" "$blue" &
        sleep $sleep
        i=$(($i + $step))
    done
}

in_transition="${4:-2000}"
in_step="${5:-1}"

fade "$in_step" "$in_transition" "$start_r" "$start_g" "$start_b" "$1" "$2" "$3"