Operating system configuration - visuve/SykeroLabs3 GitHub Wiki

Basics

• In order to make the PWM and 1-Wire to work /boot/firmware/config.txt needs to be stabbed.
  • Add the following lines to it:
    • dtoverlay=pwm,pin=12,func=4
    • For Bosch BME680 dtoverlay=i2c-sensor,bme680,addr=0x77
      • For Dallas DS18B20 dtoverlay=w1-gpio,gpiopin=4 (Not in use in this project anymore)
    • Note the pin configuration and config.txt below
  • See https://github.com/dotnet/iot/blob/main/Documentation/raspi-pwm.md and https://www.waveshare.com/wiki/Raspberry_Pi_Tutorial_Series:_1-Wire_DS18B20_Sensor for more details.

Access

• To allow SykeroLabs to control PWM, create/edit /etc/udev/rules.d/99-com.rules and add:

SUBSYSTEM=="pwm*", PROGRAM="/bin/sh -c '\
        chown -R root:gpio /sys/class/pwm && chmod -R 770 /sys/class/pwm;\
        chown -R root:gpio /sys/devices/platform/soc/*.pwm/pwm/pwmchip* && chmod -R 770 /sys/devices/platform/soc/*.pwm/pwm/pwmchip*\
'"

Power optimization

• I found the Raspberry Pi 5 to consume too much power
  • With these optimizations I managed to reduce the consumption by about half a watt

1. Underclocking the Raspberry seems to yield best results
   • See config.txt below
   • Note that reducing the clocks below arm_freq_min (i.e. 1500) or gpu_freq_min (i.e. 500) seems to have no effect, which is also noted in the official documentation
2. Disable the onboard leds
   • See config.txt below
   • Note that this works somewhat poorly with the current kernel and will turn the power led just red...
3. You can disable services which are not used by this project:
   • Bluetooth
     • sudo systemctl disable bluetooth.service
     • Also note the dtoverlay=disable-bt below
   • ModemManager
     • sudo systemctl disable ModemManager.service
4. Manually set the power supply size
   • Run sudo rpi-eeprom-config --edit and add PSU_MAX_CURRENT=3000
     • See Raspberry Pi documentation on bootloader configuration and PSUs for more details
   • This does not necessarily affect the power consumption if your PSU was small enough in the first place

Full /boot/firmware/config.txt

# I do not care about monitors or audio;
# this is a headless setup

auto_initramfs=1
camera_auto_detect=0
display_auto_detect=0
disable_fw_kms_setup=1
disable_overscan=1
disable_splash=1
dtparam=audio=off
enable_tvout=0

arm_64bit=1

# Underclock

arm_boost=0
arm_freq=1500
gpu_freq=500

# Configure PWM & 1-Wire

dtoverlay=pwm,pin=12,func=4
# dtoverlay=w1-gpio,gpiopin=4
dtoverlay=i2c-sensor,bme680,addr=0x77
dtoverlay=disable-bt

# Configure ADC for TDS/EC sensors
dtoverlay=ads1115,addr=0x48
dtparam=cha_enable
dtparam=cha_datarate=0
dtparam=chb_enable
dtparam=chb_datarate=0

# Disable leds

dtparam=pwr_led_trigger=none
dtparam=act_led_trigger=none
dtparam=pwr_led_activelow=off
dtparam=act_led_activelow=off

# Limit USB current

usb_max_current_enable=0