How to read/write all RasPi4 GPIO from basic?

I have a pico wired to a pi4 and I set out to start looking at ways to implement a byte wide communication channel between them for the eventual aim of adapting Andrew Gordon’s https://github.com/arg08/picoeco code to function as an Econet interface for the pi.

I am going to have to deal with this in assembler in the pi eventually but for a start I was just going to do it in basic so I could concentrate more on the pico side of the code initially.

I was sure I had done this before and after a bit of head scratching I think I have come to understand that on a pi 1 or 2 I have used a GPIO module from http://www.tankstage.co.uk/Software/ (version 0.6) or packman version 0.5, but this is not the GPIO module present in RISC OS which appears to have the same swi names but only about a quarter of the functionally. The tankstage one does not appear to know what a Pi4 is.

So no joy there.

Does anybody know an example of some minimal basic assembler to assess the GPIO peripheral directly?
Are the addresses given in BCM2835-ARM-Peripherals.pdf valid for RISC OS in supervisor mode?
Many thanks
Alan

I have written a module to add back some of the other functions of the original GPIO module.
I started this quite a while ago and cannot remember how far I got!
I know that the setup file save and load does not work, but most other things probably do.
In software you just call GPIOX instead of GPIO.
The module is now on my website, but use at your own risk…

Tank,
thank you for that I have downloaded it. Is there source too, I know I have read the source to your module in the past but non of your downloads include it now. I was hopeful of borrowing your code that does the pi version detection and works out the peripheral base addresses. I decided to skip doing it in BASIC and just write a module. I cobbled together a spi lcd screen driver from various sources about 6 years ago but its detection code which I think came in a PiSPI module is now broken. I can’t ever work out what its doing from the modern hal api documentation, but the rest of the code served as a good boiler plate for a module.
Alan

The GPIOX module does not access the hardware directly, but uses the new HAL interface to talk to the hardware.
The source to the original GPIO module is on the GitLab site Here