After I uploaded this, I realised the hardware schematic below does not need this software at all. The Pi has a GPIO fan built right into the OS. It is so much easier to use. Please use that insead. Run the
raspi-configcommand and see https://www.raspberrypi.com/documentation/computers/configuration.html.
A rust service to drive a PWM fan.
Apparently it uses the Channel::Pwm0 pin. Refer to rppal documentation and
the raspberry pi documentation to find out what that means.
Note that dtoverlay=pwm must be added somewhere in /boot/config.txt for this
to work. Note that this will prevent the analog audio output from working. See
more details about setup here
https://docs.rs/rppal/latest/rppal/pwm/index.html
Also note that software PWM is used by the linux kernel... I dont know what the performance implications of that are. Seems like a bummer to me if you want maximim performance out of your PI.
For the fan I used a level shifter was required. Note that in the diagram below, the fan shares the same ground as the PI.
.───.
/ \
┌┴───────┴┐
│ │
│ 2N7000 │
│ │
│ S G D │
└─┬──┬──┬─┘
┌─────────────┐ │ │ │ ┌─────────┐
│ GPIO18 PWM0 ├───────────┤ │ ├─────────┤ FAN PWM │
└─────────────┘ │ │ │ └─────────┘
┌─────────────┐ │ │ │ ┌─────────┐
│ 3.3V ├──┬─<10kΩ>─┘ │ └─<10kΩ>──┤ 5V │
└─────────────┘ └───────────┘ └─────────┘
┌────────────────────────────────────────────────────────────────────────┐
│ ┌───────┬──────┬─┬─┬─┬───────────────┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┐ │
│ │ │ 4) 5V│ │ │ │12) GPIO18 PWM0│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │
│ ├───────┼──────┼─┼─┼─┼───────────────┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤ │
│ │1) 3.3V│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │
│ └───────┴──────┴─┴─┴─┴───────────────┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘ │
│ .~~. .~~. │
│ '. \ ' ' / .' │
│ .~ .~~~..~. │
│ : .~.'~'.~. : │
│ ~ ( ) ( ) ~ │
│ ( : '~'.~.'~' : ) │
│ ~ .~ ( ) ~. ~ │
│ ( : '~' : ) │
│ '~ .~~~. ~' │
│ '~' │
└────────────────────────────────────────────────────────────────────────┘
echo TODO: I forgot how I got systemd to run this on startup :(