Re: PWM GPIO on Raspberry Pi 3
Brad Spencer <[email protected]>
| Newsgroups | gmane.os.netbsd.general,gmane.os.netbsd.ports.arm |
|---|---|
| Message-ID | <[email protected]> |
Benny Siegert <[email protected]> writes: > Hi! > > I added a 5V PWM fan to my RPi 3 running 10.1 in 32 bit mode, as > earmv7hf. I connected the PWM control pin to GPIO18, as per the article > in > https://blog.driftking.tw/en/2019/11/Using-Raspberry-Pi-to-Control-a-PWM-Fan-and-Monitor-its-Speed/. > > The thing is, I can only switch the fan on and off from there. I'd like > to use the actual PWM facility to run it at lower speeds. > > How is PWM GPIO supposed to work? I found a thread from 2019 that > suggests that the hardware PWM on the RPi3 would need driver support > that we do not have. > > For software PWM, I tried this command that I found in the manpage: > > gpioctl gpio0 attach gpiopwm 18 1 > > which results in "invalid argument". > > I think the gpiopwm driver is not loaded, but there doesn't seem to be a > module for it either. > > Any hints? You will have to compile your own kernel for that driver because as you have found, it doesn't exist as a module. The man page for gpiopwm does suggest the lines that would need to be added to a kernel config file. It could be something as simple as this (assuming you are using earmv7hf, if you are using earmv6hf use RPI2 on the include line): ---- include "arch/evbarm/conf/GENERIC" gpiopwm* at gpio? offset 18 mask 1 ---- Related to this... in the next couple or maybe few months I will probably be committing drivers for the EMC-210x and EMC-230x fan controller chips (at least some, if not most, of the members of those families). At least for the EMC-2101 a breakout board that is reasonability priced exists from Adafruit. Those will allow hardware fan PWM control and tach, and probably some temperature stuff, for anything that can do I2C. -- Brad Spencer - [email protected]