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

Thank you so much! spent quite a while looking for something like this. Works great on my pi 4 with ubuntu 18.04. Installation was easy and everything is much quieter. Thanks again!

this may be a dumb question but is there an easy way to change the temperature targets?

Ah, problem. There seems to be no control over the fan when running on the 64bit Raspbian OS. Fan is running flat out and the 3rd item in the run file is always 0.0
I guess this might take some fiddling.

{Later}
OK, not a software issue, happily. Turns out that gpio13 - at least on my Pi 4 running 64 bit OS and as soldered to a prototyping board - does not seem to provide the PWM signal. As soon as I moved the connection to gpio18 it works perfectly.

I don't have one of these fans. I cobbled together a 2n2222a transistor to the pwm pin. (With a flyback diode, etc.) For my basic 2 wire fan, (which appears to be a brushless DC Fan Model GF3007BS 5V 0.1A) the pwm frequency is too high for the fan to start. The pwm does work as expected and the signal is correct at the fan. If one increases the divider on bcm2835_pwm_set_clock(1024) it works for more plebian fans. Unfortunately this is in hearing range. Setting the pwm frequency around 100 Hz isn't too objectionable.

Unfortunately, I have to report that now both PWM pins, GPIO#13 and GPIO#18 are dead. Drawing 2.6mA=(3.3V-0.7V)/980ohms has resulted in both GPIO pins being stuck at 0. This seems pretty fragile. My adapter only used GPIO#18, so I am at a loss as to why GPIO#13 isn't functional. Pins and functionality were measured with a Siglent SDS1202X-E oscilloscope.

So I can report the background service appears to be running, but the GPIO pins are no longer functional. Guess, I'll have to revert to powering the fan @100% off the 3.3V, which was where I started.

I may try an open loop PWM script (in the bcm2835-1.68 directory) to confirm if the pwm pins are destroyed.

Just tested pwm.c - the GPIO pin#18 is fine. For some reason the PWM frequency doesn't match what is stated. pwm.c claims that it will generate a 1.1 KHz waveform. Instead it runs at 3.3 KHz, with CLOCK_DIVIDER_16. When the duty cycle is long enough, the fan starts up. Now need to dig into your main routine - there is some sort of bug that my setup has found.

FYI, I am running on an RPI4B-2GB with Raspberry Pi OS 32bit.

No bug. The service didn't restart correctly. Killed that and all of the above works, save for changing the line in the code to lower the pwm clock rate. bcm2835_pwm_set_clock(BCM2835_PWM_CLOCK_DIVIDER_512);

A very nice piece of work! There are some subtleties in the choice of duty factor and temperatures that I didn't initially appreciate.

But the service is not starting correctly after a reboot :(
If I stop and start it using sudo systemctl stop pi_fan_hwpwm followed by a start, I get no pwm control
If I then try running pwm, the pwm pin works. Then if I stop and start the service, it finally works (controls the pwm pin).

Can't figure out why the service isn't coming up correctly after a reboot. I'd like to put this on a RPI4 based NAS, but so far this setup hasn't earned my trust. I've built two HW modules - they both work the same. The SW sometimes fails to deliver a pwm signal to the pin - even though cat /run/pi_fan_hwpwm.state is reporting a PWM signal!

After a cold start #systemctl shows pi_fan_hwpwm.service is loaded active and running. However there is no physical pwm pin active.
pwm state is 89.6, but no activity at the pin, it is 0 volts. Not good.

If the service is running what would interfere with the pwm? Could it be the audio defaulting to analog which might take over the pin? At the moment I am testing headless.

The following are services that might be audio related.
alsa-restore.service is loaded active exited Save/Restore Sound card state
also-state.service is load active running Manage Sound Card State (restore and store)
sys-devices-platform-soc-fe00b840.mailbox-bcm2835_audio-sound-card0.device is loaded active and plugged (what does that mean?)

pwm does not survive reboot, nor shutdown on my system.

Found the problem. bcm2835 is silently failing after a restart. If one deletes all references to pwm1 in the source and recompiles only using pwm0 (GPIO#18), the service and functionality do survive reboot. With both GPIO#18 and GPIO#13 enabled (as in the source code above) the fan does not come on after a reboot (& hot condition).

Oblique reference to silent failure in bcm2835.h
If the library runs with any other effective UID (ie not root), then
bcm2835_init() will attempt to open /dev/gpiomem, and, if
successful, will only permit GPIO operations. In particular,
bcm2835_spi_begin() and bcm2835_i2c_begin() will return false and all
other non-gpio operations may fail silently or crash.

To me, this indicates that bcm2835 has been known to silently fail...

I want to change
#define ON_TEMP 65.
#define OFF_TEMP 60. pls

@alwynallan Thank you so much for your program. I was so annoyed by the "official" configuration of the fan. The high pitched fan nosie hunted me in my dreams. Though I still hear the fan, when the CPU is under moderate load it's still much better than before.

I followed your instruction and everything worked.

Here are my sys Info:
Linux rbpi 5.10.17-v8+ #1421 SMP PREEMPT Thu May 27 14:01:37 BST 2021 aarch64 GNU/Linux

One freature request would be a config file for the temperatures and rpms. So that you can change them without recompiling the program. Because I think the pi can run up to 80 degrees Celsius without throttling the CPU.

It would be great if your solution could find its way into the official raspi-config. But I don't know if your solution fits their idea of what "should" be in the program.

On 2021-06-24, at 6:41 AM, Daniel Volz ***@***.***> wrote: @DanielVolz commented on this gist. One freature request would be a config file for the temperatures and rpms. So that you can change them without recompiling the program. Because I think the pi can run up to 80 degrees Celsius without throttling the CPU.

A very good idea; a .fan file is a nice prospect.

It would be great if your solution could find its way into the official raspi-config. But I don't know if your solution fits their idea of what "should" be in program.

Now that there is an official fan on sale they might well be interested.It's working very well with the Noctua 40mm fan I bought tim -- tim Rowledge; ***@***.***; http://www.rowledge.org/tim M$ are grinning pigs in a sea of buggy code - The Inquirer

Thanks a lot! Worked for me!

Thank you, works perfectly on Ubuntu 20.04 on RPI4

I added code to instrument this tiny service for monitoring with Prometheus. Unless you're already using Prometheus/Grafana it's probably best to ignore this, and the default is to not use the code in this this update. To use it, get it running using my previous recipe, then

  $ sudo apt-get update
  $ sudo apt-get install ca-certificates curl gnupg lsb-release
  $ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
  $ echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
  $ sudo apt-get update
  $ sudo apt-get install docker-ce docker-ce-cli containerd.io
  $ sudo apt install cmake libmicrohttpd-dev
  $ cd
  $ git clone https://github.com/digitalocean/prometheus-client-c.git
  $ cd prometheus-client-c
  $ ./auto build
  $ sudo make
  $ sudo make install
  $ cd ~/1c13096c4cd675f38405702e89e0c536
  $ nano Makefile
    INSTRUMENT_FOR_PROMETHEUS := true
  $ make
  $ sudo make install
  $ curl localhost:8764/metrics

Thank you so much for this! Worked perfectly for a 64-bit Ubuntu server Raspberry Pi 8GB. As for the Prometheus integration, should I first get Prometheus running via its docker image and target the port you specify here (8764) or is this prometheus-client-c a standalone version?

EDIT: It seems I can't build the Prometheus C client, it gave me a Make error on the step GOPATH in the Dockerfile:

+ GOPATH=/gopath /usr/local/go/bin/go get github.com/prometheus/prom2json
/bin/sh: 1: /usr/local/go/bin/go: Exec format error
The command '/bin/sh -c set -x &&     apt-get update && ... &&     chmod +x /entrypoint &&     GOPATH=/gopath /usr/local/go/bin/go get github.com/prometheus/prom2json && ... &&     rm -rf /var/lib/apt/lists/*' returned a non-zero code: 2
make: *** [Makefile:2: docker] Error 2

Check this to fix it

hi,
I am using RPI 4 8GB model headless with Raspberry Pi OS Lite 64bit installed. I have this fan installed and connected to GPIO 18 pin.
My system is up to date.
I can follow your guide up to this point
$ sudo apt install -y build-essential git stress-ng
$ cd
$ wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.68.tar.gz
$ tar zxvf bcm2835-1.68.tar.gz
$ cd bcm2835-1.68
$ ./configure
$ make
$ sudo make install
$ cd
$ git clone https://gist.github.com/1c13096c4cd675f38405702e89e0c536.git
$ cd 1c13096c4cd675f38405702e89e0c536

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 have tried a few times but I am kind of lost here on what to do next.

Is there an issue with the file/format or do you think I don't have the right hardware to follow this through?

Please let me know.

Best,
V

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.