#!/bin/bash

#
# My Odroid fan control script
# (only tested with an Odroid HC4 running Manjaro)
#

# Information (don't touch unless you're me)
NAME="odroid-fancontrol.sh"
AUTHOR="david@socialnerds.org"
VERSION="0.2.1"
LICENSE="MIT"
DESCRIPTION="$NAME (v$VERSION) controls the fan speed in an Odroid HC4 (and possibly others) based on temperature. It is written by $AUTHOR and published under the $LICENSE license."

# Configuration
THRESHOLD=50000
DISTANCE=1000
INTERVAL=30
STEPS=(120 160 210 255)
FAN="/sys/class/hwmon/hwmon2/pwm1"
LOGFILE="/var/log/hc4_fancontrol.log"

# Get all temperature readings and return the highest value
function get_temp() {
  local TEMPS=($(cat /sys/devices/virtual/thermal/thermal_zone*/temp))
  local RESULT=${TEMPS[0]};
  for TEMP in ${TEMPS[@]}; do
    if [ $TEMP -gt $RESULT ]; then
      RESULT=$TEMP
    fi
  done
  echo $RESULT
}

# Get current fan speed
function get_speed() {
  local SPEED=$(cat $FAN)
  echo $SPEED
}

# Set new fan speed
function set_speed() {
  local CURRENT_SPEED=$(get_speed)
  local NEW_SPEED=$1
  if [ $CURRENT_SPEED -ne $NEW_SPEED ]; then
    echo $NEW_SPEED > $FAN
    if [ -n $LOGFILE ]; then
      echo "$(date +%Y%m%d-%H%M%S): Temp[$(get_temp)], Speed[$(get_speed)]" >> $LOGFILE
    fi
    sleep 3
  fi
}

# Set fan mode to manual
echo "disabled" | tee /sys/class/thermal/thermal_zone{0,1}/mode > /dev/null

# Run loop
while true; do
  TEMP=$(get_temp)
  SPEED=$(get_speed)
  NEW_THRESHOLD=$THRESHOLD
  if [ $TEMP -gt $THRESHOLD ]; then
    for STEP in ${STEPS[@]}; do
      if [ $TEMP -gt $NEW_THRESHOLD ]; then
        NEW_THRESHOLD=$((NEW_THRESHOLD + DISTANCE))
        if [ $SPEED -lt $STEP ]; then
          set_speed $STEP
        fi
      fi
    done
  else
    set_speed 0
  fi
  sleep $INTERVAL
done