fanControl.c

/**************************************************************************************

        COMPILE USING : gcc -Wall -o fanControl fanControl.c -lwiringPi -lpthread
                and give it root privileges as wiringPi needs it to control PWM fan.
                To do so, you can :
                        1/ run it as root (duh)
                        2/ Use some stickybits shenanigans to give it root privileges
                           regardless of whoever is running it by typing :
                                chown root.root fanControl
                                chmod 4755 fanControl
                (and add the program to the super user crontab to avoid
                running it manually everytime you reboot your pi)

***************************************************************************************/


#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdlib.h>

#include <wiringPi.h>

typedef struct fanMode
{
	int temp;
	int speed;
} fanMode;



// Temperature variables
FILE* tempfile; // file containing tmp value (refreshed by system)
int curTemp; // current Temperature of the rpi in °C
// Refresh rate in second
int refreshRate = 5;
// fan Speed
bool fanStatus = true; // determine is fan is on or off
// fanMode settings (temperature and according speed fan)
fanMode fanModeList[] = {
        {.temp=0, .speed=0},            // don't turn on the fan until temperature hits 70°C
        {.temp=70000, .speed=930},	// 70°C / 930
        {.temp=73000, .speed=964},	// 73°C / 964
        {.temp=75000, .speed=980},	// 75°C / 980
        {.temp=79000, .speed=1024}      // go fullSpeed if we're hitting 79,000°C
                         };
int curFM = 4; // start at fm4, fullspeed



int actualizeTemp()
{
	tempfile = fopen ("/sys/class/thermal/thermal_zone0/temp", "r");
	fscanf (tempfile, "%d", &curTemp);
        fclose (tempfile);
	return curTemp;
}

void displayInfo()
{
	// Display informations (for debug purproses)
        printf("current FanMode: %i \n", curFM);
        printf("Temperature: %i \n", curTemp);
        printf("Fan Speed: %i \n", fanModeList[curFM].speed);
        printf("------------------------ \n");
}



int main()
{
        /**** DELAY STARTUP ****/
        // delay the program by argv[1] milliseconds, in case some programs
        // may hijack GPIO pins in between the start of the program and the main loop
        // let's say at startup, or use the delay and some scripting to reclaim GPIO
        // pins from others faulty programs *cough* Mupen64 *cough*
        if (argc >= 2)
                delay(atoi(argv[1]));

	/**** INIT ****/
	// check if wiringPi loaded correctly
	if (wiringPiSetup () == -1)
	{
		fprintf (stderr, "Unable to setup GPIO: %s\n", strerror (errno)) ;
		return 1 ;
	}
	// set pin control mode for pin 1/pwm/gpio18/fan
	pinMode (1, PWM_OUTPUT) ;
	// set fan at fullspeed by default during the initialization
	pwmWrite(1, 1024);

	/**** MAIN LOOP ****/
	while(1)
	{
		// Actualize the temperature
	        actualizeTemp();

		/**********************************
                 *             MAGIKU             *
                 **********************************/

		// Increasing Fan mode (if fan is not already at max && temp reached next FanMode temperature)
		if ( curFM < 4 && curTemp > fanModeList[curFM+1].temp )
		{
			curFM++;

			// if fan was off give it a little burst to kick in and change flag status
			if( !fanStatus )
			{
				pwmWrite(1, 1024);
				fanStatus = true;
				sleep(1);
			}
			// speed up fan accordingly accordingly to new FanMode
			pwmWrite(1, fanModeList[curFM].speed);
		}
		// Decreasing Fan mode (if fan is not already at min && temp is below current FanMode temperature)
		else if ( curFM > 0 && curTemp < fanModeList[curFM].temp )
		{
			curFM--;

			// if fan needs to turn off shutit down and change the fanStatus flag
			if( curFM <= 0 )
			// set the flag
				fanStatus = false;
			// slow down fan accordingly to new FanMode
                       pwmWrite(1, fanModeList[curFM].speed);
		}

		// Display informations about current fan setting (FanMode, Temperature, FanSpeed)
		// Debug Purposes only
		// displayInfo();

		// Go back to sleep
		sleep(refreshRate);
	}

	/**** SHUTDOWN ****/
	return 0;
}