# !/bin/sh
# K.H. Jensen 2008 // www.hartvig.de
# Released under the GPL
# eeefan version 2 - eee pc fan control utility

temperature_reading=/proc/eee/temperature
fan_control=/proc/eee/fan_speed
fan_manual_switch=/proc/eee/fan_manual

# Set critical temperature 
TEMP_CRITICAL=57

# Set critical temperature interval size. See figure for details
TEMP_INTERVAL_SIZE=5

# Maximum fan speed
FAN_SPEED_MAX=55

eeefanupdate() {
    # Get temperature reading
    TEMP=$(cat $temperature_reading)
    # Calculate optimum fan speed
    X=$(echo "$FAN_SPEED_MAX*1/(1+e(-($TEMP-$TEMP_CRITICAL)/$TEMP_INTERVAL_SIZE))" | bc -q -l)
    # Workaround to convert it to nearest integer
    FAN_SPEED=$(echo "scale=0; $X/1.0" | bc -q -l)
    # Set fan speed
    echo $FAN_SPEED > $fan_control
}
# cron jobs can only be executed once every minute,
# so we have to use the sleep command
# Turn on manual fan control
echo 1 > $fan_manual_switch
# Run eeefanu, then wait 10 seconds.
eeefanupdate
sleep 10
eeefanupdate
sleep 10
eeefanupdate
sleep 10
eeefanupdate
sleep 10
eeefanupdate