Better Fan control for Argon One Raspberry Pi 4 case

argonone_fan.conf

## This is config for Argon controllable fan

## Temperature at which fan starts
t_on = 50

## Temperature at which fan has full speed
t_full = 65

## Temperature difference for cooldown curve.
## Basically fan will start to slow down when temperature drops by this amount.
t_delta = 5.0

## FAN minimal speed, lowest value at which fan starts spinning.
s_min = 0

## FAN maximum speed, defaults to full speed i.e. 100, set lower if fan noise bothers you too much.
s_max = 100

## Temperature read interval in seconds
interval = 10

argonone_fan.py

#!/usr/bin/python3

"""
Argon One Fan Controller.

Installation
------------

Put this file in /usr/bin/argonone_fan, remeber to give it execution flag (chmod u+x). Configuration file
goes to /etc/argonone_fan.conf. To enable system daemon copy serive file to /etc/systemd/system/argonone_fan.service
and execute:

  sudo systemctl daemon-reload
  sudo systemctl enable argonone_fan
  sudo systemctl start argonone_fan
 
To see logs run:

  sudo journalctl -fu argonone_fan

Principle of operation
----------------------

Fan starts spinning at starting temperature (ON) speed increases lineary with temperature until reaching max at
end temperature (FULL). If temperature rises and begins to lower PWM will not decrease until temp drops
by configured delta (D). This is most common situation (const), where temperature oscilates around fixed value.
With this type of controll you get quick reaction for temperature increase and minial speed variations
in stable conditions.

     ^ fan speed
100% -
     |
 MAX -                ---<---------<>--
     |               /          /
     |    (cooling) /          /
     |             /          /
     |            /          /
     |           /          /
     |          / (const)  /
     |         / ---<>--- /
     |        /          / (heating)
     |       / <- D ->  /
 MIN -      /          /
     |     |          |
     |     |          |
  0% +--<>------>-----|----------|------->
                      ON         FULL    T

"""

import logging
import time

import smbus
import RPi.GPIO as GPIO

rev = GPIO.RPI_REVISION
if rev == 2 or rev == 3:
    bus = smbus.SMBus(1)
else:
    bus = smbus.SMBus(0)

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)

logger = logging.getLogger(__name__)
logging.basicConfig(level=logging.INFO, format='%(message)s')


def _interp1(val, in0, in1, out0, out1):
    """Linear interpolation"""
    return (val - in0) * (out1 - out0) / (in1 - in0) + out0


def _interp1_sat(val, in0, in1, out0, out1, sin0=None, sin1=None, sout0=None, sout1=None):
    """Linear interpolation with saturation.

    in0, in1     : input range
    out0, out1   : output range
    sin0, sin1   : saturation input bounds (default in0, in1)
    sout0, sout1 : saturation output bounds (default out0, out1)

    out =
        sout0 if val < sin0
        sout1 if val >= sin1
        (out0, out1) if val in (in0, in1)
    """
    if sin0 is None:
        sin0 = in0
    if sin1 is None:
        sin1 = in1
    if sout0 is None:
        sout0 = out0
    if sout1 is None:
        sout1 = out1

    if in0 < in1:
        assert sin0 <= sin1
    else:
        assert sin0 >= sin1

    if out0 < out1:
        assert sout0 <= sout1
    else:
        assert sout0 >= sout1

    if val < sin0:
        return sout0
    elif val >= sin1:
        return sout1
    else:
        ret = _interp1(val, in0, in1, out0, out1)
        if ret > sout1:
            return sout1
        elif ret < sout0:
            return sout0
        else:
            return ret


def get_temp():
    try:
        with open("/sys/class/thermal/thermal_zone0/temp", "r") as tempfp:
            temp = tempfp.readline()
        return float(int(temp) / 1000)
    except IOError:
        return 0


def read_config():
    config = {
        'on': 50,
        'full': 60,
        'delta': 2,
        'min': 10,
        'max': 100,
        'interval': 10,
    }
    try:
        with open("/etc/argonone_fan.conf") as configfp:
            config_raw = configfp.read()
    except FileNotFoundError:
        pass
    else:
        for lineno, line in enumerate(config_raw.splitlines()):
            line = line.strip()
            if line.startswith('#') or len(line) == 0:
                continue
            try:
                key, value = line.split('=', maxsplit=1)
            except ValueError:
                logger.warning('Invalid syntax in config file on line %d', lineno + 1, exc_info=True)
                continue
            key = key.strip()
            value = value.strip()
            try:
                if key == 't_on':
                    config['on'] = float(value)
                elif key == 't_full':
                    config['full'] = float(value)
                elif key == 't_delta':
                    config['delta'] = float(value)
                elif key == 's_min':
                    config['min'] = float(value)
                elif key == 's_max':
                    config['max'] = float(value)
                elif key == 'interval':
                    config['interval'] = float(value)
                else:
                    logger.warning('Unknown config key %s', key)
            except ValueError:
                logger.warning('Invalid config value for %s', key, exc_info=True)
                continue

    return config


def set_fanspeed(speed):
    address = 0x1a
    try:
        bus.write_byte(address, speed)
    except IOError:
        pass


def temp_check():
    config = read_config()
    logger.info('Starting temperature daemon, %.1f°C/%.1f°C ±%.1f°C %d-%d%%',
                config['on'], config['full'], config['delta'], config['min'], config['max'])
    logger.info('Current core temperature %.1f°C', get_temp())
    set_fanspeed(0)
    lasttemp = 0
    lastspeed = 0
    speeddown_from = None
    speedup_from = None
    while True:
        temp = get_temp()
        if temp != lasttemp:
            temp0 = config['on']
            temp1 = config['full']
            speed0 = config['min']
            speed1 = config['max']
            speedmin = 0
            speedmax = config['max']

            if temp < lasttemp:
                speedup_from = None
                if speeddown_from is None:
                    speeddown_from = lastspeed
                speedmax = speeddown_from
                temp0 = config['on'] - config['delta']
                temp1 = config['full'] - config['delta']
            else:
                speeddown_from = None
                if speedup_from is None:
                    speedup_from = lastspeed
                speedmin = speedup_from

            lasttemp = temp

            logger.debug('%.1f, %d, %d, %d, %d, %d, %d', temp, temp0, temp1, speed0, speed1, speedmin, speedmax)
            speed = round(_interp1_sat(temp, temp0, temp1, speed0, speed1, sout0=speedmin, sout1=speedmax))
            if speed != lastspeed:
                lastspeed = speed
                set_fanspeed(speed)
                logger.info('FAN speed updated T=%.1f°C PWM=%d%%', temp, speed)
        time.sleep(config['interval'])


def main():
    try:
        temp_check()
    except KeyboardException:
        pass
    finally:
        GPIO.cleanup()


if __name__ == '__main__':
    main()

argonone_fan.service

[Unit]
Description=Argon One Fan Service
After=multi-user.target

[Service]
Type=simple
Restart=always
RemainAfterExit=true
ExecStart=/usr/bin/argonone_fan

[Install]
WantedBy=multi-user.target