boards/rpi-pico: add support

[tprrt]

Description

Add the support for the mcu RP2040 as weel as the Raspberry-Pi Pico board.

Raspberry Pi Pico is a low-cost, high-performance microcontroller board with flexible digital interfaces. Key features include:

RP2040 microcontroller chip designed by Raspberry Pi in the United Kingdom
Dual-core Arm Cortex M0+ processor, flexible clock running up to 133 MHz
264KB of SRAM, and 2MB of on-board Flash memory
Castellated module allows soldering direct to carrier boards
USB 1.1 with device and host support
Low-power sleep and dormant modes

Drag-and-drop programming using mass storage over USB
26 × multi-function GPIO pins
2 × SPI, 2 × I2C, 2 × UART, 3 × 12-bit ADC, 16 × controllable PWM channels
Accurate clock and timer on-chip
Temperature sensor
Accelerated floating-point libraries on-chip
8 × Programmable I/O (PIO) state machines for custom peripheral support

Useful links

https://www.raspberrypi.org/blog/raspberry-pi-silicon-pico-now-on-sale
https://www.raspberrypi.org/documentation/pico/getting-started/
https://raspberrypi.github.io/pico-sdk-doxygen/index.html

[aabadie]

See #16609

[maribu]

Maybe we can keep the issue open a bit to sync who's working on which feature

[maribu]

• periph_timer: @fabian18 is working on this, cpu/rpx0xx: add periph timer #16627 is already in pretty good shape
• DMA: @maribu is working on a HAL for memory to memory transfers (that should also be possible to implement for other MCUs) and some low level helper functions that should aid other RPx0xx peripheral drivers in implementing transfers from and to memory mapped I/O
• periph_uart: Basic support is upstream, @maribu is working on DMA support as a test use case
• periph_spi: See cpu/rpx0xx: implement periph_spi #19440 by @fengelhardt
• `periph_i2c: ?
• periph_adc: See cpu/rpx0xx: add initial ADC support #19516 (@dylad)
• periph_pwm: See cpu/rpx0xx: add initial pwm support #20473 (@dylad)
• periph_pm: ?
• periph_usb: ?
• periph_pio: I think @fabian18 did take a look into it. It certainly is one of the more interesting features of the MCU, IMO.

[krzysztof-cabaj]

I have tried to flash RPI-pico using uf2conv programmer, using the command:

make BOARD=rpi-pico PROGRAMMER=uf2conv flash

Unfortunately, nothing happened after a successful compilation, linking, and coping UF2 file. After some inspection, I found that UF2 file generated by uf2conv program is incompatible with RPI-pico UF2 bootloader. Everything worked fine when I converted the generated elf file using elf2uf2 tool from pico-SDK and manually copied it to the flash. After some investigation, I detect minor changes in the each UF2 block header between images generated by uf2conv and elf2uf2. If details are needed, I could provide them.

Currently, after some hardcoded changes in RIOT makefiles, I could program the board using elf2uf2 conversion tool (instead of uf2conv) without any problems.

My RPI-pico is using an older RP2-B1 chip. If this problem appears in the most recent RP2-B2 chip version (unfortunately, I have no access to this version) I could add elf2uf2 tool to RIOT code.

[smurfix]

Is anybody working on enhancing this? there seem to be some missing peripherals …

[fabian18]

Is anybody working on enhancing this? there seem to be some missing peripherals …

Any unassigned peripheral is probably waiting to be implemented. Right now, I have more important work to do, than to continue to implement PIO support. Do you require any particular peripheral, or are you asking in general?

[smurfix]

Besides PIO, ADC support would be nice to have, at least for my current project.

[fengelhardt]

I am working on SPI support right now. I can maybe add some more, it seems not that difficult.

[dylad]

I've started to work on an ADC driver for this MCU.

[dylad]

periph_pwm is my next target.

[MacT900]

I'm new here. Can I add i2c?

[benpicco]

Sure, go ahead!
Currently I2C is implemented via PIO, but afaik there is also a native I2C peripheral in the RP2040

[maribu]

yes there is :-) And @fabian18 already has already created the stubs where it would call to either PIO or native I2C implementation.

Thanks for picking this up :-)

[MacT900]

Can I ask questions here or should I ask in forum? How and from what I create branch or pull request?

[dylad]

If you have a question about something related to RP2040 (hardware or software). You can ask it here.
Otherwise, if you have questions about RIOT itself, or something else, it would be better to go to the forum. (This way this issue can focus on RP2040 only).

I strongly suggest you to have a look at a few entries in our wiki regarding RIOT development and contribution:
How to make a pull request
Contribution guidelines
Coding Conventions

Feel free to join us on Matrix, we might also help you there.

[studiosoftdev]

I'm currently doing a bachelors degree level project and intend to check some items off this list - looking at starting with pwm or i2c, then pm, usb and pio if there's no existing implementation for that. Posting here to ask what the current state of these features are so I don't try and do something that someone else is already doing :)

[dylad]

I have the periph_pwm almost ready. Just need to do some testing on my side. Don't waste time on it ;)

[MacT900]

Hi, I'm back from little break. Should I add an option to use I2C as a slave and where I can find info about I2C drive strength?

[dylad]

Hi @MacT900,
In the current state, RIOT doesn't support I2C slave. There is discussion about this here
Regarding I2C drive strength, you could either set it to a compile-time default value in periph_cpu.h or create a special field in the I2C configuration structure defined in periph_conf.h. The current I2C API doesn't handle pull strength selection in the current state.

[dylad]

periph_pwm support was just merged.

[fengelhardt]

I will give periph_usbus a try.

[dylad]

I will give periph_usbus a try.

That's nice ! I have some experience with this, so don't hesitate to ask if you need help or have any questions.

[fengelhardt]

I have my periph_usbus code almost ready. However, I have doubts if I understood correctly what the two event handlers should do, and what should happen in the ISR and in the xmit functions.

Maybe I could push my code as a WIP Pull Request to clarify?

The code is compiling but not working at all. I just ordered a Black Magic Probe for debugging just in case 😄

[dylad]

Please go ahead.
That's something I can help to polish.
No promises on how fast I'll be but that's something I'd like to see merged

[tanneberger]

@dylad @MacT900 @benpicco

I am right now building an application for which I require I2C running on the pico. What is the status of your implementation? I am happy to test your WIP implementations ;D

[dylad]

@tanneberger
Currently the easiest way to use I2C on rpi-pico is through PIO.

There is an open PR for hardware I2C opened by @studiosoftdev at #20677 but they didn't answer to review yet.

[tanneberger]

@dylad I tried using I2C and I think it uses the PIO under the hood, but that crashes the kernel when calling i2c_init.

I will also try out that PR thank you.

[dylad]

@tanneberger If you encountered an issue with I2C/PIO on RP2040, please open an issue to describe it. It should works at out of the box (at least that was the case last time I played with it).
If some regressions were introduced, I can have a look at it and try to fix it soon.

[tanneberger]

@dylad I created Issue #21187