Pi GPIO - PWM Pins

A quick question, but is there a way to control the ‘hardware’ PWM on the Pi’s GPIO pins? I can set it to PWM mode, but GPIO_Write seems to have no effect.

If I set the pin to GPIO mode I can turn it off and on manually, but I don’t really want to so software PWM.

Cheers

Chris

Hi Chris a quick question can Python 3.10.0a5+ load pyserial? and if it can how do i load it

Are you trying this on a Pi3 or a Pi4? As far as I can see, changing mode is broken to some extent in RISC OS on the Pi4. I’ve been trying to change the mode of pins to redirect pwm audio out via the GPIO. This works fine on all earlier versions of the Pi but not on the Pi4 using RISC OS. I can do it from Linux, so the hardware still supports it.

This is a very interesting thread not least because I have a stash of modules, HATs, servos etc that I have bought very recently and would like to bring to life using BASIC if possible.
So far I have managed to get a basic DC motor going with a “Maker Drive” (blatant misuse of the English Language but great hardware) from Cytron. Running a servo though requires a PWM signal. I have figured that there are two ways to do this:

1. Creating the signal directly from the GPIO
2. Attaching a HAT (I have PiBorg’s UltraBorg) and communcating over the 12C protocol. The HAT would then creat the PWM signal.

Regarding the second option…
PiBorg have published their code
https://www.piborg.org/blog/build/ultraborg-build/ultraborg-examples

Can we communicate via the 12C on BBC BASIC? I guess the goal would be to mimic the signal the code creates would it be possible technically?

PS my misuse of the english language is, although prevalent, unintentional

Can we communicate via the 12C on BBC BASIC?

Yes. I do it to talk to an IIC – 1-wire adapter. The IIC bit was easy, the 1-wire part more tricky.

The program is here: http://www.adamshome.org.uk/RiscOS/templogger.zip

The bit you probably want is called onewirelib. It uses the older IIC_Control SWI. The IIC_Op SWI is preferred, but it made it more difficult to debug the one-wire bots. The older interface does things one step at a time. The newer one stacks things into groups.

Hi Chris a quick question can Python 3.10.0a5+ load pyserial? and if it can how do i load it

I’ve started having another look at 3.10, so tried pyserial. It seems that out of the box it doesn’t work because it doesn’t know how to handle RISC OS serial ports – fair point I guess.

I’m not sure what would be involved in making it work, either by DeviceFS (which would proably be easiest and would handle at least USB serial devices) or with the block drivers.

From memory, the block drivers involve loading a chunk of code into your own program and calling it via an entry point. I’m not sure python can do this as it stands – although it could probably be made to do so via a C veneer.