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Hardware PWM Controller for the Raspberry Pi 4 Case Fan
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, 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);
}
[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
@alwynallan
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alwynallan commented Dec 9, 2020

This program drives the Raspberry Pi 4 Case Fan with hardware pulse width modulation (PWM) so that the fan runs quieter and the CPU experiences gentler thermal cycles than with the firmware (dtoverlay=gpio-fan,gpiopin=14,temp=80000) option. This program uses < 0.1% of a core when running, compared with 12% for software PWM. Only two exposed GPIO pins are capable of hardware PWM (GPIO 13 and GPIO 18) and one them (GPIO 13) interferes with the Case Fan bracket, so GPIO 18 is the best choice. The blue wire from the fan needs to be moved 2 places down for GPIO 18.
PXL_20201209_112238363

The program runs as root and creates two files for monitoring: /run/pi_fan_hwpwm.pid and /run/pi_fan_hwpwm.state . The latter file contains three numbers e.g. '1337, 68.95, 74.3' representing the loops (~1 sec) since starting, the smoothed core temperature, and the PWM level in percent. The PWM runs at 20 kHz, generally acceptable for fans and not annoying to pets or children.

@alwynallan
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alwynallan commented Dec 9, 2020

[For context see Jeff Geerling's Blog.]

Here is a comparison of the thermal response under stress using no fan, firmware control, and PWM control.
image
Stress script: https://gist.github.com/geerlingguy/91d4736afe9321cbfc1062165188dda4

@alwynallan
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alwynallan commented Dec 9, 2020

This Gist is easy to install:

$ 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
$ make
$ sudo make install

Then watch it work:

$ stress-ng -c 4 -t 3m -q & watch -n1 cat /run/pi_fan_hwpwm.state

And Ctrl+C when done.

I tested it on the latest Ubuntu 20.04 64-bit and Raspbian Pi OS Lite 32-bit. Let me know about others. The /boot configuration changes suggested in the .c source are not necessary.

@JohanSF
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JohanSF commented Jan 13, 2021

Hi there,

I installed this according to the instructions and rebooted my pi. The fan still just runs no matter what the temperature is, is that expected behavior?

When I run sudo ./pi_fan_hwpwm -v I get this:
image
My guess is that the second column is temperature, so is this the stress test I'm running here?

Should I put the run command somewhere that runs it upon boot?

@alwynallan
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alwynallan commented Jan 14, 2021

@JohanSF
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JohanSF commented Jan 14, 2021

Yes it is exactly like that. And it does work when I run sudo ./pi_fan_hwpwm -v, but that also starts the test and stresses the cpu. It seems that it doesn't start correctly at boot, perhaps a permissions issue?

@tedsluis
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tedsluis commented Jan 17, 2021

Hi, I tried this on a raspberry 4b 8GB with fedora 64bit. I have only little experience with gpio and this would be a great solution for controlling my adda ad0205dx-k59 fans, but I was not able to get it running.

I have downloaded and unpacked your tar file:

[tedsluis@fed127 fan]$  wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.68.tar.gz                                                                                                                                                       
--2021-01-17 11:45:55--  http://www.airspayce.com/mikem/bcm2835/bcm2835-1.68.tar.gz                                                                                                                                                           
Resolving www.airspayce.com (www.airspayce.com)... 192.185.48.187                                                                                                                                                                             
Connecting to www.airspayce.com (www.airspayce.com)|192.185.48.187|:80... connected.                                                                                                                                                          
HTTP request sent, awaiting response... 200 OK                                                                                                                                                                                                
Length: 272796 (266K) [application/x-gzip]                                                                                                                                                                                                    
Saving to: ‘bcm2835-1.68.tar.gz’                                                                                                                                                                                                              
                                                                                                                                                                                                                                              
bcm2835-1.68.tar.gz       100%[=============================>] 266.40K   375KB/s    in 0.7s     
                                                                                                                                                                                                                                              
2021-01-17 11:45:56 (375 KB/s) - ‘bcm2835-1.68.tar.gz’ saved [272796/272796]                                                                                                                                                                  
                                                                                                                                                                                                                                              
[tedsluis@fed127 fan]$ tar zxvf bcm2835-1.68.tar.gz 

I have installed gcc using the fedora dnf package manager:
[tedsluis@fed127 bcm2835-1.68]$ sudo dnf install gcc -y
Next I did run:

[tedsluis@fed127 bcm2835-1.68]$ ./configure                                                                         
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /usr/bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether make supports the include directive... yes (GNU style)
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking whether gcc understands -c and -o together... yes
checking dependency style of gcc... gcc3
checking for clock_gettime in -lrt... yes
checking for doxygen... no
configure: WARNING: Doxygen not found - continuing without Doxygen support
checking for ranlib... ranlib
checking for gcc... (cached) gcc
checking whether we are using the GNU C compiler... (cached) yes
checking whether gcc accepts -g... (cached) yes
checking for gcc option to accept ISO C89... (cached) none needed
checking whether gcc understands -c and -o together... (cached) yes
checking dependency style of gcc... (cached) gcc3
checking that generated files are newer than configure... done
configure: creating ./config.status
config.status: creating Makefile
config.status: creating src/Makefile
config.status: creating doc/Makefile
config.status: creating config.h
config.status: executing depfiles commands

Next I have run make:

[tedsluis@fed127 bcm2835-1.68]$ make
make  all-recursive
make[1]: Entering directory '/home/tedsluis/fan/bcm2835-1.68'
Making all in src
make[2]: Entering directory '/home/tedsluis/fan/bcm2835-1.68/src'
gcc -DHAVE_CONFIG_H -I. -I..     -g -O2 -MT bcm2835.o -MD -MP -MF .deps/bcm2835.Tpo -c -o bcm2835.o bcm2835.c
mv -f .deps/bcm2835.Tpo .deps/bcm2835.Po
rm -f libbcm2835.a
ar cru libbcm2835.a bcm2835.o 
ranlib libbcm2835.a
make[2]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68/src'
Making all in doc
make[2]: Entering directory '/home/tedsluis/fan/bcm2835-1.68/doc'
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68/doc'
make[2]: Entering directory '/home/tedsluis/fan/bcm2835-1.68'
make[2]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68'
make[1]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68'
[tedsluis@fed127 bcm2835-1.68]$ sudo make install
Making install in src
make[1]: Entering directory '/home/tedsluis/fan/bcm2835-1.68/src'
make[2]: Entering directory '/home/tedsluis/fan/bcm2835-1.68/src'
 /usr/bin/mkdir -p '/usr/local/lib'
 /usr/bin/install -c -m 644  libbcm2835.a '/usr/local/lib'
 ( cd '/usr/local/lib' && ranlib libbcm2835.a )
 /usr/bin/mkdir -p '/usr/local/include'
 /usr/bin/install -c -m 644 bcm2835.h '/usr/local/include'
make[2]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68/src'
make[1]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68/src'
Making install in doc
make[1]: Entering directory '/home/tedsluis/fan/bcm2835-1.68/doc'
make[2]: Entering directory '/home/tedsluis/fan/bcm2835-1.68/doc'
make[2]: Nothing to be done for 'install-exec-am'.
make[2]: Nothing to be done for 'install-data-am'.
make[2]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68/doc'
make[1]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68/doc'
make[1]: Entering directory '/home/tedsluis/fan/bcm2835-1.68'
make[2]: Entering directory '/home/tedsluis/fan/bcm2835-1.68'
make[2]: Nothing to be done for 'install-exec-am'.
make[2]: Nothing to be done for 'install-data-am'.
make[2]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68'
make[1]: Leaving directory '/home/tedsluis/fan/bcm2835-1.68'

Next I installed the packages using dnf (fedora package manager):

[tedsluis@fed127 bcm2835-1.68]$ cd ~/fan                                                                                                                                                                                                      
[tedsluis@fed127 fan]$ sudo dnf install -y git stress-ng                                                                                                                                                                                      
Last metadata expiration check: 2:37:40 ago on Sun 17 Jan 2021 09:11:53 AM CET.                                                                                                                                                               
Package git-2.29.2-3.fc33.aarch64 is already installed.
Dependencies resolved.
================
 Package                                                    Architecture                                          Version                                                         Repository                                             Size
=============
Installing:
 stress-ng                                                  aarch64                                               0.12.01-1.fc33                                                  updates                                               518 k
Installing dependencies:
 Judy                                                       aarch64                                               1.0.5-24.fc33                                                   fedora                                                131 k
 lksctp-tools                                               aarch64                                               1.0.18-6.fc33                                                   fedora                                                 94 k

Transaction Summary
=============
Install  3 Packages

Total download size: 743 k
Installed size: 2.3 M
Downloading Packages:
(1/3): Judy-1.0.5-24.fc33.aarch64.rpm                                                                                                                                                                         418 kB/s | 131 kB     00:00    
(2/3): lksctp-tools-1.0.18-6.fc33.aarch64.rpm                                                                                                                                                                 293 kB/s |  94 kB     00:00    
(3/3): stress-ng-0.12.01-1.fc33.aarch64.rpm                                                                                                                                                                   1.5 MB/s | 518 kB     00:00    
-----------------------------------------------------------------
Total                  678 kB/s | 743 kB     00:01     
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                                                                                                                      1/1 
  Installing       : lksctp-tools-1.0.18-6.fc33.aarch64                                                                                                                                                                                   1/3 
  Running scriptlet: lksctp-tools-1.0.18-6.fc33.aarch64                                                                                                                                                                                   1/3 
  Installing       : Judy-1.0.5-24.fc33.aarch64                                                                                                                                                                                           2/3 
  Installing       : stress-ng-0.12.01-1.fc33.aarch64                                                                                                                                                                                     3/3 
  Running scriptlet: stress-ng-0.12.01-1.fc33.aarch64                                                                                                                                                                                     3/3 
  Verifying        : stress-ng-0.12.01-1.fc33.aarch64                                                                                                                                                                                     1/3 
  Verifying        : Judy-1.0.5-24.fc33.aarch64                                                                                                                                                                                           2/3 
  Verifying        : lksctp-tools-1.0.18-6.fc33.aarch64                                                                                                                                                                                   3/3 

Installed:
  Judy-1.0.5-24.fc33.aarch64                                                lksctp-tools-1.0.18-6.fc33.aarch64                                                stress-ng-0.12.01-1.fc33.aarch64                                               

Complete!

Next I cloned your files and run the make and make install:

[tedsluis@fed127 fan]$ git clone https://gist.github.com/1c13096c4cd675f38405702e89e0c536.git
Cloning into '1c13096c4cd675f38405702e89e0c536'...
remote: Enumerating objects: 75, done.
remote: Total 75 (delta 0), reused 0 (delta 0), pack-reused 75
Receiving objects: 100% (75/75), 9.77 KiB | 1.63 MiB/s, done.
Resolving deltas: 100% (28/28), done.
[tedsluis@fed127 fan]$ cd 1c13096c4cd675f38405702e89e0c536/
✔ tedsluis@fed127 ~/fan/1c13096c4cd675f38405702e89e0c536 [master|✔] $ ls -l
total 16
4 -rw-r--r--. 1 tedsluis tedsluis  685 Jan 17 11:50 Makefile
8 -rw-r--r--. 1 tedsluis tedsluis 5025 Jan 17 11:50 pi_fan_hwpwm.c
4 -rw-r--r--. 1 tedsluis tedsluis  269 Jan 17 11:50 pi_fan_hwpwm.service
✔ tedsluis@fed127 ~/fan/1c13096c4cd675f38405702e89e0c536 [master|✔] $ make
gcc -Wall -o pi_fan_hwpwm pi_fan_hwpwm.c -lbcm2835
✔ tedsluis@fed127 ~/fan/1c13096c4cd675f38405702e89e0c536 [master|…1] $ ll
total 212
  4 -rw-r--r--. 1 tedsluis tedsluis    685 Jan 17 11:50 Makefile
196 -rwxr-xr-x. 1 tedsluis tedsluis 228464 Jan 17 11:50 pi_fan_hwpwm
  8 -rw-r--r--. 1 tedsluis tedsluis   5025 Jan 17 11:50 pi_fan_hwpwm.c
  4 -rw-r--r--. 1 tedsluis tedsluis    269 Jan 17 11:50 pi_fan_hwpwm.service
✔ tedsluis@fed127 ~/fan/1c13096c4cd675f38405702e89e0c536 [master|…1] $ ls -l pi_fan_hwpwm
196 -rwxr-xr-x. 1 tedsluis tedsluis 228464 Jan 17 11:50 pi_fan_hwpwm

✔ tedsluis@fed127 ~/fan/1c13096c4cd675f38405702e89e0c536 [master|…1] $ sudo make install
install pi_fan_hwpwm /usr/local/sbin
cp pi_fan_hwpwm.service /etc/systemd/system/
systemctl enable pi_fan_hwpwm
Created symlink /etc/systemd/system/multi-user.target.wants/pi_fan_hwpwm.service → /etc/systemd/system/pi_fan_hwpwm.service.
! systemctl is-active --quiet pi_fan_hwpwm || systemctl stop pi_fan_hwpwm
systemctl start pi_fan_hwpwm

The install went well, but the executable won't run (as root):

[root@fed127 ~]# systemctl status pi_fan_hwpwm
● pi_fan_hwpwm.service - Hardware PWM control for Raspberry Pi 4 Case Fan
     Loaded: loaded (/etc/systemd/system/pi_fan_hwpwm.service; enabled; vendor preset: disabled)
     Active: failed (Result: exit-code) since Sun 2021-01-17 11:51:14 CET; 38min ago
    Process: 111394 ExecStart=/usr/local/sbin/pi_fan_hwpwm (code=exited, status=1/FAILURE)
   Main PID: 111394 (code=exited, status=1/FAILURE)
        CPU: 9ms

Jan 17 11:51:14 fed127 systemd[1]: pi_fan_hwpwm.service: Scheduled restart job, restart counter is at 5.
Jan 17 11:51:14 fed127 systemd[1]: Stopped Hardware PWM control for Raspberry Pi 4 Case Fan.
Jan 17 11:51:14 fed127 systemd[1]: pi_fan_hwpwm.service: Start request repeated too quickly.
Jan 17 11:51:14 fed127 systemd[1]: pi_fan_hwpwm.service: Failed with result 'exit-code'.
Jan 17 11:51:14 fed127 systemd[1]: Failed to start Hardware PWM control for Raspberry Pi 4 Case Fan.

It has execute permissions:

[root@fed127 ~]# ll /usr/local/sbin/pi_fan_hwpwm
196 -rwxr-xr-x. 1 root root 228464 Jan 17 11:51 /usr/local/sbin/pi_fan_hwpwm

Here the journal:

[root@fed127 ~]# journalctl --unit pi_fan_hwpwm
-- Logs begin at Sat 2020-11-21 19:53:17 CET, end at Sun 2021-01-17 12:19:29 CET. --
Jan 17 11:51:12 fed127 systemd[1]: Started Hardware PWM control for Raspberry Pi 4 Case Fan.
Jan 17 11:51:12 fed127 pi_fan_hwpwm[111361]: bcm2835_init: gpio mmap failed: Operation not permitted
Jan 17 11:51:12 fed127 pi_fan_hwpwm[111361]: bcm2835_init() failed
Jan 17 11:51:12 fed127 systemd[1]: pi_fan_hwpwm.service: Main process exited, code=exited, status=1/FAILURE
Jan 17 11:51:12 fed127 systemd[1]: pi_fan_hwpwm.service: Failed with result 'exit-code'.
Jan 17 11:51:13 fed127 systemd[1]: pi_fan_hwpwm.service: Scheduled restart job, restart counter is at 1.
Jan 17 11:51:13 fed127 pi_fan_hwpwm[111390]: bcm2835_init: gpio mmap failed: Operation not permitted
Jan 17 11:51:13 fed127 pi_fan_hwpwm[111390]: bcm2835_init() failed
Jan 17 11:51:13 fed127 systemd[1]: Stopped Hardware PWM control for Raspberry Pi 4 Case Fan.
Jan 17 11:51:13 fed127 pi_fan_hwpwm[111392]: bcm2835_init: gpio mmap failed: Operation not permitted
Jan 17 11:51:13 fed127 pi_fan_hwpwm[111392]: bcm2835_init() failed
Jan 17 11:51:13 fed127 systemd[1]: Started Hardware PWM control for Raspberry Pi 4 Case Fan.
Jan 17 11:51:13 fed127 systemd[1]: pi_fan_hwpwm.service: Main process exited, code=exited, status=1/FAILURE
Jan 17 11:51:13 fed127 systemd[1]: pi_fan_hwpwm.service: Failed with result 'exit-code'.

I am not able to execute it manual:

[root@fed127 ~]# /usr/local/sbin/pi_fan_hwpwm                                                                          
bcm2835_init: gpio mmap failed: Operation not permitted                                                                
bcm2835_init() failed  

Also the with -v option the same error is returned.

Using strace I see this:

[root@fed127 ~]# strace /usr/local/sbin/pi_fan_hwpwm  
execve("/usr/local/sbin/pi_fan_hwpwm", ["/usr/local/sbin/pi_fan_hwpwm"], 0xffffcdb10840 /* 21 vars */) = 0
brk(NULL)                               = 0x128c6000
faccessat(AT_FDCWD, "/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=32146, ...}) = 0
mmap(NULL, 32146, PROT_READ, MAP_PRIVATE, 3, 0) = 0xffff9acfb000
close(3)                                = 0
openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0\267\0\1\0\0\0\360J\2\0\0\0\0\0"..., 832) = 832
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\351\32\275\235t2\376Ww\37\0~\370\373\257<"..., 68, 768) = 68
fstat(3, {st_mode=S_IFREG|0755, st_size=3125592, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xffff9acf9000
mmap(NULL, 1596208, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xffff9ab41000
mprotect(0xffff9aca8000, 90112, PROT_NONE) = 0
mmap(0xffff9acbe000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16d000) = 0xffff9acbe000
mmap(0xffff9acc4000, 11056, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xffff9acc4000
close(3)                                = 0
mprotect(0xffff9acbe000, 12288, PROT_READ) = 0
mprotect(0x41f000, 4096, PROT_READ)     = 0
mprotect(0xffff9ad06000, 4096, PROT_READ) = 0
munmap(0xffff9acfb000, 32146)           = 0
getpid()                                = 113109
openat(AT_FDCWD, "/run/pi_fan_hwpwm.pid", O_RDWR|O_CREAT, 0666) = 3
fcntl(3, F_SETLK, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
ftruncate(3, 0)                         = 0
write(3, "113109\n", 7)                 = 7
close(3)                                = 0
brk(NULL)                               = 0x128c6000
brk(0x128e7000)                         = 0x128e7000
brk(NULL)                               = 0x128e7000
openat(AT_FDCWD, "/proc/device-tree/soc/ranges", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=48, ...}) = 0
read(3, "~\0\0\0\0\0\0\0\376\0\0\0\1\200\0\0|\0\0\0\0\0\0\0\374\0\0\0\2\0\0\0"..., 4096) = 48
close(3)                                = 0
geteuid()                               = 0
openat(AT_FDCWD, "/dev/mem", O_RDWR|O_SYNC) = 3
mmap(NULL, 25165824, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0xfe000000) = -1 EPERM (Operation not permitted)
write(2, "bcm2835_init: gpio mmap failed: "..., 56bcm2835_init: gpio mmap failed: Operation not permitted
) = 56
close(3)                                = 0
write(2, "bcm2835_init() failed\n", 22bcm2835_init() failed
) = 22
exit_group(1)                           = ?
+++ exited with 1 +++

Do you have any idea what can be wrong? I very much appreciate any help!

@tedsluis
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tedsluis commented Jan 25, 2021

I found out why I am not able to use this solution. It uses the legacy interface /sys/class/gpio, still available in raspios and some other distros. Several other Linux distros, like Fedora 32+ are already compiled without this legacy interface, so there’s no /sys/class/gpio on the system. They use the new character device /dev/gpiochipN provided by the upstream kernel.

I found a python module that is using the new /dev/gpiochipN interface. check my solution here: https://github.com/tedsluis/raspberry-pi-pwm-fan-control

Anyway, thanks for all the provided info!

@timrowledge
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timrowledge commented Mar 16, 2021

Thanks very much for this. So far it works perfectly well with a Noctua 41x10 fan just connected to the +5/gnd/gpio18 pins with no extra fiddling.
I find myself wondering about paying with the transfer function and using hysterisis curves and reading the cpu usage stats to predicitvely spool up the fan... another rabbit hole to plunge into some day. In the meantime, it will make life a lot quieter; those Noctua fans on full power are surprisingly loud.

@trevhull
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trevhull commented Mar 16, 2021

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?

@timrowledge
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timrowledge commented Mar 17, 2021

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.

@bdlabitt
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bdlabitt commented Mar 17, 2021

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.

@bdlabitt
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bdlabitt commented Mar 17, 2021

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.

@bdlabitt
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bdlabitt commented Mar 17, 2021

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

@bdlabitt
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bdlabitt commented Mar 17, 2021

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.

@bdlabitt
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bdlabitt commented Mar 17, 2021

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!

@bdlabitt
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bdlabitt commented Mar 18, 2021

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.

@bdlabitt
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bdlabitt commented Mar 20, 2021

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...

@hahieuhass
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hahieuhass commented May 16, 2021

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

@DanielVolz
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DanielVolz commented Jun 24, 2021

@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.

@timrowledge
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timrowledge commented Jun 24, 2021

@Alexeykib
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Alexeykib commented Oct 5, 2021

Thanks a lot! Worked for me!

@chengkuangan
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chengkuangan commented Nov 24, 2021

Thank you, works perfectly on Ubuntu 20.04 on RPI4

@alwynallan
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Author

alwynallan commented Feb 24, 2022

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

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