Hardware PWM Controller for the Raspberry Pi 4 Case Fan

Makefile

CC = gcc
RM = rm -f

INSTRUMENT_FOR_PROMETHEUS := false

ifeq ($(INSTRUMENT_FOR_PROMETHEUS),true)
  CFLAGS  = -Wall -DINSTRUMENT_FOR_PROMETHEUS
  LIBS    = -lbcm2835 -lprom -lpromhttp -lmicrohttpd
else
  CFLAGS  = -Wall
  LIBS    = -lbcm2835
endif

TARGET = pi_fan_hwpwm

all: $(TARGET)

$(TARGET): $(TARGET).c Makefile
        $(CC) $(CFLAGS) -o $(TARGET) $(TARGET).c $(LIBS)

install: $(TARGET)
        install $(TARGET) /usr/local/sbin
        cp $(TARGET).service /etc/systemd/system/
        systemctl enable $(TARGET)
        ! systemctl is-active --quiet $(TARGET) || systemctl stop $(TARGET)
        systemctl start $(TARGET)

uninstall: clean
        systemctl stop $(TARGET)
        systemctl disable $(TARGET)
        $(RM) /usr/local/sbin/$(TARGET)
        $(RM) /etc/systemd/system/$(TARGET).service
        $(RM) /run/$(TARGET).*
        @echo
        @echo "To remove the source directory"
        @echo "    $$ cd && rm -rf ${CURDIR}"
        @echo

clean:
        $(RM) $(TARGET)

pi_fan_hwpwm.c

/*
/
/ pi_fan_hwpwm.c, alwynallan@gmail.com 12/2020, no license
/ latest version: https://gist.github.com/alwynallan/1c13096c4cd675f38405702e89e0c536
/
/ Need    http://www.airspayce.com/mikem/bcm2835/index.html
/
/ Compile $ gcc -Wall pi_fan_hwpwm.c -lbcm2835 -o pi_fan_hwpwm
/
/ 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
/             enable_uart=0                              <- needed? not Ubuntu
/             dtparam=audio=off                          <- needed? not Ubuntu
/             dtparam=i2c_arm=off                        <- needed? not Ubuntu
/             dtparam=spi=off                            <- needed? not Ubuntu
/
/ Run     $ sudo ./pi_fan_hwpwm -v
/
/ Forget  $ sudo ./pi_fan_hwpwm &
/         $ 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 <bcm2835.h>

//#define INSTRUMENT_FOR_PROMETHEUS do this in the Makefile

#ifdef INSTRUMENT_FOR_PROMETHEUS
  // https://github.com/digitalocean/prometheus-client-c
  #define PROM_PORT 8764
  #include <signal.h>
  #include "microhttpd.h"
  #include "prom.h"
  #include "promhttp.h"
  prom_counter_t *pi_fan_hwpwm_loops;
  prom_gauge_t *pi_fan_hwpwm_temp;
  prom_gauge_t *pi_fan_hwpwm_pwm;
#endif //INSTRUMENT_FOR_PROMETHEUS

#define PWM_PIN   0  // default, uses both GPIO 13 and GPIO 18
#define HIGH_TEMP 80.
#define ON_TEMP   65.
#define OFF_TEMP  60.
#define MIN_FAN   150
#define KICK_FAN  200
#define MAX_FAN   480

unsigned pin = PWM_PIN;
int verbose = 0;
int fan_state = 0;
double temp = 25.0;
pid_t global_pid;
int pwm_level = -555;

void usage()
{
   fprintf
   (stderr,
      "\n" \
      "Usage: sudo ./pi_fan_hwpwm [OPTION]...\n" \
      "\n" \
      "  -g <n> Use GPIO n for fan's PWM input, default 0 (both).\n" \
      "         Only hardware PWM capable GPIO 18 and GPIO 13 are present on\n" \
      "         the RasPi 4B pin header, and only GPIO 18 can be used with\n" \
      "         the unmodified case fan.\n" \
      "  -v     Verbose output\n" \
      "\n"
   );
}

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 PWM_out(int level) {
  if(level > pwm_level && (level - pwm_level) < 5) return;
  if(level < pwm_level && (pwm_level - level) < 10) return;
  if(level != pwm_level) {
    if(pin == 0 || pin == 13) bcm2835_pwm_set_data(1, level);
    if(pin == 0 || pin == 18) bcm2835_pwm_set_data(0, level);
    pwm_level = level;
  }
}

void fan_loop(void) {
  if(!fan_state && (temp > ON_TEMP)) {
    PWM_out(KICK_FAN);
    fan_state = 1;
    return;
  }
  if(fan_state && (temp < OFF_TEMP)) {
    PWM_out(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 > MAX_FAN) out = MAX_FAN;
    PWM_out(out);
  }
}

#ifdef INSTRUMENT_FOR_PROMETHEUS
void ae1() {
  prom_collector_registry_destroy(PROM_COLLECTOR_REGISTRY_DEFAULT);
}
struct MHD_Daemon *mhdDaemon;
void ae2() {
  MHD_stop_daemon(mhdDaemon);
}
#endif //INSTRUMENT_FOR_PROMETHEUS

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 != 0 && pin != 13 && pin != 18) 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_hwpwm.pid", buf);

  if(!bcm2835_init()) fatal(0, "bcm2835_init() failed");
  if(pin==0 || pin==13) bcm2835_gpio_fsel(13, BCM2835_GPIO_FSEL_ALT0);
  if(pin==0 || pin==18) bcm2835_gpio_fsel(18, BCM2835_GPIO_FSEL_ALT5);
  bcm2835_pwm_set_clock(2); // 19.2 / 2 MHz
  if(pin==0 || pin==13) bcm2835_pwm_set_mode(1, 1, 1);
  if(pin==0 || pin==13) bcm2835_pwm_set_range(1, 480);
  if(pin==0 || pin==18) bcm2835_pwm_set_mode(0, 1, 1);
  if(pin==0 || pin==18) bcm2835_pwm_set_range(0, 480);
  PWM_out(0);
#ifdef INSTRUMENT_FOR_PROMETHEUS
  prom_collector_registry_default_init();
  pi_fan_hwpwm_loops = prom_collector_registry_must_register_metric(
    prom_counter_new("pi_fan_hwpwm_loops", "Control loop counter.", 0, NULL));
  pi_fan_hwpwm_temp = prom_collector_registry_must_register_metric(
    prom_gauge_new("pi_fan_hwpwm_temp", "Core temperature in Celsius.", 0, NULL));
  pi_fan_hwpwm_pwm = prom_collector_registry_must_register_metric(
    prom_gauge_new("pi_fan_hwpwm_pwm", "Fan speed PWM in percent.", 0, NULL));
  promhttp_set_active_collector_registry(NULL);
  atexit(ae1);
  mhdDaemon = promhttp_start_daemon(MHD_USE_SELECT_INTERNALLY, PROM_PORT, NULL, NULL);
  if (mhdDaemon == NULL) exit(EXIT_FAILURE);
  else                   atexit(ae2);
#endif //INSTRUMENT_FOR_PROMETHEUS

  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, %.1f\n", loop/4, temp, (float)pwm_level/(float)MAX_FAN*100.);
      run_write("/run/pi_fan_hwpwm.state", buf);
      if(verbose) fputs(buf, stdout);
#ifdef INSTRUMENT_FOR_PROMETHEUS
      prom_counter_inc(pi_fan_hwpwm_loops, NULL);
      prom_gauge_set(pi_fan_hwpwm_temp, temp, NULL);
      prom_gauge_set(pi_fan_hwpwm_pwm, (double)pwm_level/(double)MAX_FAN*100., NULL);
#endif //INSTRUMENT_FOR_PROMETHEUS
    }
    usleep(250000);
  }

  exit(EXIT_SUCCESS);
}

pi_fan_hwpwm.service

[Unit]
Description=Hardware PWM control for Raspberry Pi 4 Case Fan
After=syslog.target

[Service]
Type=simple
User=root
WorkingDirectory=/run
PIDFile=/run/pi_fan_hwpwm.pid
ExecStart=/usr/local/sbin/pi_fan_hwpwm
Restart=on-failure

[Install]
WantedBy=multi-user.target

But when I follow the next step of make, I get the following error - " Makefile:19: *** missing separator (did you mean TAB instead of 8 spaces?). Stop."

@vincentkenny01 I've had the same error, the Makefile here is erroneously indented with spaces instead of a tab. You must replace manually those spaces with tabs on the Makefile.

Would it be possible for you to share your makefile with me otherwise I'll have to figure out a way of doing this without spending hours.

…

-------- Original message -------- From: Jose Sarmento ***@***.***> Date: 19/07/2022 15:41 (GMT+00:00) To: alwynallan ***@***.***> Cc: vincentkenny01 ***@***.***>, Manual ***@***.***> Subject: Re: alwynallan/Makefile @josejsarmento commented on this gist.

________________________________ But when I follow the next step of make, I get the following error - " Makefile:19: *** missing separator (did you mean TAB instead of 8 spaces?). Stop." I've had the same error, the Makefile here is erroneously indented with spaces instead of a tab. You must replace manually those spaces with tabs on the Makefile. — Reply to this email directly, view it on GitHub<https://gist.github.com/1c13096c4cd675f38405702e89e0c536#gistcomment-4237630>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ACGKX2VT6RIZQLQYU6ZYCVLVU25A7ANCNFSM4UTLG5OA>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

@vincentkenny010 You can check my fork of this gist, I have indented correctly the Makefile there.

I think a project such as this deserves its own repo on Github, don't you think @alwynallan ? It's a feature highly requested on the internet, and there's so few working and efficient implementations of this. A repo would allow for pull requests and for issues discussions such as these.

Thanks for this. Much appreciated, I will have a go tomorrow at compiling this. On the same note, did you turn off the option of enabling the fan at a certain temperature from the config.txt file (raspi-condig>perofrmance>fan) or did you leave it on? I don't know if it will cause an issue having two programs managing the fan. I've been playing with the docker version of pwm but much prefer the hardware version due to low cpu cycling.

…

-------- Original message -------- From: Jose Sarmento ***@***.***> Date: 19/07/2022 15:53 (GMT+00:00) To: alwynallan ***@***.***> Cc: vincentkenny01 ***@***.***>, Mention ***@***.***> Subject: Re: alwynallan/Makefile @josejsarmento commented on this gist.

________________________________ @vincentkenny010 You can check my fork of this gist<https://gist.github.com/josejsarmento/41dc1fba134b31e0b429c67747e5a4cd>, I have indented correctly the Makefile there. I think a project such as this deserves its own repo on Github, don't you think @alwynallan<https://github.com/alwynallan> ? It's highly requested on the internet, and there's so few working and efficient implementations of this. A repo would allow for pull requests for issues such as these. — Reply to this email directly, view it on GitHub<https://gist.github.com/1c13096c4cd675f38405702e89e0c536#gistcomment-4237644>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ACGKX2XQ3MRWJODPLL2CANDVU26PRANCNFSM4UTLG5OA>. You are receiving this because you were mentioned.Message ID: ***@***.***>

I've just updated a Pi4 to Bookworm and can't compile this because bcm2835.h is not found. Searching with
find / -mount -name bcm28*.h -print
says it isn't there for reals.
WTF?
Did I forget to install some prerequisite?

D'OH! Yes. Missed the entire wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.68.tar.gz thing etc. All done.