Using a RasPi pico with Nerves

Sebb · February 19, 2021, 3:21am

The RPi Pico is based on the RP2040-Microcontroller, which is a Cortex-M0+. While its the biggest M0 I know of (lots of RAM, Flash, MHz) its still a very limited design, most notably: it has no FPU.

The most lightweight option AtomVM offers is a STM32F4 which is a Cortex-M4 with FPU.

github.com

bettio/AtomVM/blob/master/README.STM32.Md

# AtomVM for STM32

## Prerequisites
To flash both AtomVM and your packed AVM you must use st-flash (https://github.com/texane/stlink). Make sure to
follow its [installation procedure](https://github.com/texane/stlink#installation) before proceeding further.

## Building
- `git clone libopencm3`
- `cd libopencm3 && make -j4 && cd ..`
- `mkdir build`
- `cd build`
- `cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/arm-toolchain.cmake -DLIBOPENCM3_DIR=../libopencm3 ..`
- `make`

You can put libopencm3 wherever you want on your PC as long as you update LIBOPENCM3_DIR to point to it.

## Flashing
To flash AtomVM, use
```
st-flash --reset write atom-vm.bin 0x8000000

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Maybe they can go smaller? But M0 - doubtful!? If its possible this would be indeed a great opportunity and I’m sure the AtomVM-team will take it.

see here for a comparison (Table “ARM Cortex-M instruction variations”)

You should have a look at https://www.grisp.org/ if you are interested in BEAM on smaller platforms.

EDIT: Just found this: https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/is-cortex-m4-the-strongest