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@alwynallan
Last active Dec 9, 2020
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/*
Deprecated, see https://gist.github.com/alwynallan/1c13096c4cd675f38405702e89e0c536
If you have to use software PWM, it's still here.
*/
/*
/
/ pi_fan_pwm.c, alwynallan@gmail.com 12/2020, no license
/
/ Need http://abyz.me.uk/rpi/pigpio/download.html
/
/ Compile $ gcc -Wall pi_fan_pwm.c -lpigpio -lpthread -o pi_fan_pwm
/
/ Disable $ sudo nano /boot/config.txt [Raspbian, or use GUI]
$ sudo nano /boot/firmware/usercfg.txt [Ubuntu]
/ # dtoverlay=gpio-fan,gpiopin=14,temp=80000 <-------------- commented out, reboot
/
/ Run $ sudo ./pi_fan_pwm -v
/
/ Forget $ sudo ./pi_fan_pwm &
/ $ disown -a
/
*/
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdarg.h>
#include <pigpio.h>
#define PWM_PIN 14
#define HIGH_TEMP 80.
#define ON_TEMP 65.
#define OFF_TEMP 60.
#define MIN_FAN 235
#define KICK_FAN 450
#define MAX_FAN 1000
unsigned pin = PWM_PIN;
int verbose = 0;
int fan_state = 0;
double temp = 25.0;
pid_t global_pid;
void usage()
{
fprintf
(stderr,
"\n" \
"Usage: sudo ./pi_fan_pwm [OPTION]...\n" \
"\n" \
" -g <n> Use GPIO n for fan's PWM input, default %d\n" \
" -v Verbose output\n" \
"\n"
, PWM_PIN
);
}
void fatal(int show_usage, char *fmt, ...) {
char buf[128];
va_list ap;
va_start(ap, fmt);
vsnprintf(buf, sizeof(buf), fmt, ap);
va_end(ap);
fprintf(stderr, "%s\n", buf);
if (show_usage) usage();
fflush(stderr);
exit(EXIT_FAILURE);
}
void run_write(const char *fname, const char *data) {
// https://opensource.com/article/19/4/interprocess-communication-linux-storage
struct flock lock;
lock.l_type = F_WRLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0;
lock.l_pid = global_pid;
int fd;
if ((fd = open(fname, O_RDWR | O_CREAT, 0666)) < 0)
fatal(0, "failed to open %s for writing", fname);
if (fcntl(fd, F_SETLK, &lock) < 0)
fatal(0, "fcntl failed to get lock on %s", fname);
if (ftruncate(fd, 0) < 0)
fatal(0, "truncate failed to on %s", fname);
write(fd, data, strlen(data));
close(fd);
}
void fan_loop(void) {
if(!fan_state && (temp > ON_TEMP)) {
gpioPWM(pin, KICK_FAN);
fan_state = 1;
return;
}
if(fan_state && (temp < OFF_TEMP)) {
gpioPWM(pin, 0);
fan_state = 0;
return;
}
if(fan_state) {
unsigned out = (double) MIN_FAN + (temp - OFF_TEMP) / (HIGH_TEMP - OFF_TEMP) * (double)(MAX_FAN - MIN_FAN);
if(out > 1000) out = 1000;
gpioPWM(pin, out);
}
}
int main(int argc, char *argv[]) {
int opt;
unsigned loop = 0;
int t;
FILE *ft;
char buf[100];
while ((opt = getopt(argc, argv, "g:v")) != -1) {
switch (opt) {
case 'g':
pin = atoi(optarg);
if(pin > 31) fatal(0, "Invalid GPIO");
break;
case 'v':
verbose = 1;
break;
default:
usage();
exit(EXIT_FAILURE);
}
}
if(optind != argc) fatal(1, "optind=%d argc=%d Unrecognized parameter %s", optind, argc, argv[optind]);
global_pid = getpid();
sprintf(buf, "%d\n", global_pid);
run_write("/run/pi_fan_pwm.pid", buf);
gpioCfgClock(2, 1, 1);
if(gpioInitialise()<0) fatal(0, "gpioInitialise() failed");
if(gpioSetPWMfrequency(pin, 20000) != 20000) fatal(0, "PWM freqency error");
gpioSetPWMrange(pin, 1000);
gpioPWM(pin, 0);
while(1) {
loop++;
ft = fopen("/sys/class/thermal/thermal_zone0/temp", "r");
fscanf(ft, "%d", &t);
fclose(ft);
temp = 0.0001 * (double)t + 0.9 * temp;
if((loop%4) == 0) { // every second
fan_loop();
sprintf(buf, "%u, %.2f, %d\n", loop/4, temp, gpioGetPWMdutycycle(pin));
run_write("/run/pi_fan_pwm.state", buf);
if(verbose) fputs(buf, stdout);
}
usleep(250000);
}
gpioTerminate();
exit(EXIT_SUCCESS);
}
@alwynallan

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@alwynallan alwynallan commented Dec 8, 2020

[For context see Jeff Geerling's Blog.]

This works better, and quieter, than the raspberrypi.org firmware controller, and obviously better than no fan. It currently uses 12% of one core, which is an unfortunate side effect of using the pigpio library, but I'm still looking for an alternative. Also needs proper installation under systemd.

image
Stress script: https://gist.github.com/geerlingguy/91d4736afe9321cbfc1062165188dda4

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@alwynallan alwynallan commented Dec 9, 2020

Deprecated!

I have implemented hardware PWM, and started a new Gist for it https://gist.github.com/alwynallan/1c13096c4cd675f38405702e89e0c536 . It uses 50x less CPU resources than this.

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@geerlingguy geerlingguy commented Dec 9, 2020

Very nice!

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