#!/bin/bash

###########################################################################
#
# Copyright (c) 2005 Simon "Sturmflut" Raffeiner <sturmflut@lieberbiber.de>
#
# This script is published under the terms of the GNU Public license
# version 2 or later.
#
###########################################################################
#
# Version History:
#
# 29.05.2005: Initial release
#
###########################################################################


# Path to your I2C driver in SysFS
I2C_PATH=/sys/bus/i2c/devices/1-0290

# Name of the I2C device that returns the temperature we want to monitor
I2C_TEMPERATURE_INPUT=temp2_input

# Name of the PWM device to control
I2C_PWM_DEVICE=pwm1

# Minimum temperature value (your fan stops below this value)
# NOTE: My Winbond w83627hf returns temperatur values degrees*1000
TEMPERATURE_MIN=32000

# Maximum temperature value (your fan blows full speed above this value)
# NOTE: My Winbond w83627hf returns temperatur values degrees*1000
TEMPERATURE_MAX=46000

# Number of uniquesteps your PWM generator is able to generate
# NOTE: My Winbond w83627hf allows a value range from 0 to 255 in steps of 16
# so I have 16 steps (16*16 = 256)
PWM_STEPS=16

if [ ! -e $I2C_PATH ]; then
	echo "I2C Device path does not exist!"
fi

while /bin/true
do
	CPUTEMP=`cat $I2C_PATH/$I2C_TEMPERATURE_INPUT`
	FANSPEED=`cat $I2C_PATH/$I2C_PWM_DEVICE`
	
	echo "CPU Temperature: $CPUTEMP"
	echo "Fan Speed: $FANSPEED"

	# Calculate Factor
	let DIVIDER=($TEMPERATURE_MAX-$TEMPERATURE_MIN)/$PWM_STEPS
	let FACTOR=($CPUTEMP-$TEMPERATURE_MIN)/$DIVIDER
	echo "Faktor: $FACTOR"
	
	#Calculate new Fan Speed
	if [ $FACTOR -lt 1 ]; then
		FANSPEED_NEW=0
	else
	
	if [ $FACTOR -le 16 ]; then
		let FANSPEED_NEW=$FACTOR*$PWM_STEPS
	else
		FANSPEED_NEW=255;
	fi
fi

echo "New fan speed: $FANSPEED_NEW"

# Set new fan speed
echo $FANSPEED_NEW > $I2C_PATH/$I2C_PWM_DEVICE

# NOTE: I set the speed of my second fan (harddisk cage) to the same value
echo $FANSPEED_NEW > $I2C_PATH/pwm2

sleep 3
done