Documentation should include instructions on how to use/enable I2C/SPI/PWM/1-wire/...

[krwq]

Currently we are lacking gathered place where we describe how to plug in and setup Raspberry PI with I2C/SPI/PWM and other protocols. We should write instructions and start linking samples to those docs to make people easier to start.

Work left here:

• I2C instructions for Raspbian
• SPI instructions for Raspbian
• PWM instructions for Raspbian
• 1-wire instructions for Raspbian
• Links in the samples

let me know if the list is missing anything

@MarkCiliaVincenti @shaggygi

[Frankenslag]

@krwq
Perhaps be more specific and say that it's a Pi running Raspbian. I have noticed that 64bit Debian, for example, doesn't have the same device tree configuration and so the SPI configuration instructions used for Raspian aren't appropriate.

[krwq]

@Frankenslag good point, ideally we should have couple of other common OSes but I guess that's optional here. Let's make the titles generic and start with just Raspbian

[krwq]

Should we just point people to /boot/overlays/README for now? It describes how to enable everything on the PI using /boot/config.txt

[larivierec]

I'm running this on Ubuntu 19.10 and it's not enough. It's a start because it allowed me to enable pwm through the overlays however, hardware PWM is currently unsupported within dotnet as certain pins need to be in different modes in order to operate on them.

i.e.:
gpio 18 needs to be in alternate function 5 (PWM) mode in order for it to work.

[krwq]

@larivierec I'm not sure you can change the mode without root access or if it would be appropriate for .NET to change that (although if we can do it so that you can switch between PWM/GPIO without issues then I think we should allow it). For PWM without changing settings you can use SoftwarePwm

[larivierec]

@larivierec I'm not sure you can change the mode without root access or if it would be appropriate for .NET to change that (although if we can do it so that you can switch between PWM/GPIO without issues then I think we should allow it). For PWM without changing settings you can use SoftwarePwm

I guess it's totally an opinion but I believe it's important for .NET to be able to change that also, if permissions are properly set, a user could request changing the pins state. Thanks for your input!

[krwq]

@larivierec can you please file a separate issue on that? We can figure out if we should close this one there once we have enough data. If you have any info how to actually do that with i.e. SysFs please put additional info there. I don't expect that will work for all possible cases - we can likely get the GpioController which has direct memory access to do that, not sure about the rest of them.

We need to figure out how to combine GpioController with PWM on the API level as well since they are currently not tangled in the code (but are on the hardware level).

[pgrawehr]

@krwq: For Raspbian, setting the alternate pin modes is technically easy to do (using /dev/gpiomem) and is noted in #857. The infrastructure required to do it will be part of my Board proposal (not yet, though). I don't know whether Debian or Ubuntu offer /dev/gpiomem access, though.

@larivierec If you can use overlays, it should work, actually. For Raspbian, it is now also required to enable an overlay (don't recall the exact name) to make PWM initialy work. You can also use the gpio mode command from the wiringpi package.

[larivierec]

@krwq: For Raspbian, setting the alternate pin modes is technically easy to do (using /dev/gpiomem) and is noted in #857. The infrastructure required to do it will be part of my Board proposal (not yet, though). I don't know whether Debian or Ubuntu offer /dev/gpiomem access, though.

@larivierec If you can use overlays, it should work, actually. For Raspbian, it is now also required to enable an overlay (don't recall the exact name) to make PWM initialy work. You can also use the gpio mode command from the wiringpi package.

I can confirm that /dev/gpiomem is available on Ubuntu (unsure about debian).

For PWM channels, pwm-2chan must be enabled in the /boot/config.txt with dtoverlay. I also saw you referenced an issue I'll look over that documentation and thanks for that. Secondly, I don't believe going through wiringpi is the correct way to set the mode. The iot project currently offers a way to set gpio modes therefore it should probably support changing it to the alternate functions