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Introducing the Seeed Studio Wio RP2040

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Introduction

When the Raspberry Pi Foundation designed their new microcontroller, the Raspberry Pi Pico, the heart of the board is the RP2040 System on a Chip (SoC). This chip contains dual ARM Cortex-M0+ CPU cores, 296kb RAM, a number of coprocessors and a number of specialty I/O processors. Raspberry made the decision to sell this chip separately and it has since appeared on the boards from various other hardware vendors. Previously, we discussed the Adafruit Feather RP2040 and in this article is about Seeed Studio’s Wio RP2040 which is another of these boards. The Raspberry Pi Pico contains support for several wired communications protocols, but no support for wireless communications, or ethernet, making it difficult to connect directly to the Internet. Seeed Studio paired the RP2040 chip with a ESP based wireless chip, adding both WiFi and Bluetooth in a board smaller than the Pico.

Module vs Development Board

There are two versions of of the Wio RP2040 board:

  • The Wio RP2040 Module containing the RP2040
  • The Wio RP2040 Mini Dev Board which adds a bootsel button, led, usb connector, and the pins to add it to a breadboard.

If you are experimenting, I would recommend getting the development board. If you get the CPU module then at a minimum you need to solder the wires for a USB wire to the board so you can connect it to a host computer to download programs from.

I received the module version, so I learned a bit about the four wires contained in a USB cable. Fortunately, there is a standard for the wire colors, so figuring out the wiring was easy. Soldering the USB cable to the module was fiddly but doable. You also need to solder two wires for the bootsel button, you can either connect these to a button, or just touch them together to activate bootsel. If you want to debug with gdb, then you also need to connect three wires to the two SWD pins and a ground pin, to allow gdb to control the board.

Below is my module with the USB cable soldered in and two leads for the bootsel button. I should add three more wires for debugging, but this isn’t necessary if you are only using MicroPython.

Software Development

The core of this board is the RP2040 processor, so you can develop with this board using Raspberry’s RP2040 SDK. You can also use any of the environments that support the Raspberry Pi Pico like MicroPython or the Arduino system. The only restriction is that WiFi support is only officially supported with MicroPython which we talk about next.

Developing with WiFi

As of this writing, using the WiFI/Bluetooth functionality is only supported from MicroPython. Seeed supplies a custom version of MicroPython which has this module compiled in. This version leverages the work in MicroPython done for the Raspberry Pi Pico and as a consequence works with the Thonny Python IDE. This is an interesting contrast with Seeed’s Wio Terminal which doesn’t have IDE support and you need to rely on REPL for development.

The problem with this approach is that I couldn’t find the source code for this build of MicroPython, which means if I wanted to add more libraries, I don’t have a way to do this, including my own custom C and Assembly Language code. Again, contrast this to the Wio Terminal, which includes all the source code as well as a build system for adding modules and custom code. Hopefully, the source code for this MicroPython build makes it onto Seeed’s Github repository in the near future.

There is speculation on the forums that the WiFi is an ESP8266 board connected via the SPI interface and then controlled using AT commands. These are basically an extension of the old Hayes modem command set, extended to a more modern world. It wouldn’t take much documentation on Seeed’s part to provide some details, such as the SPI port used and SPI configuration parameters. With this detail it would be easy to add WiFi and/or Bluetooth support to programs written in the standard RP2040 SDK. Or better still contribute their WiFi support to the Raspberry Pi Pico Extras GitHub repository.

Summary

The Seeed Wio RP2040 is a compact module to build your projects around. The big current limitation is the lack of software support for the ESP radio module; hopefully, this will be rectified in the near future. Seeed designed this module to be included into custom PCB boards such as their dev board and offer a service to manufacture these. If this is your first Wio RP2040, then you should get the mini dev board as this is far easier to connect up and get working, then use the smaller module in your final project.

Written by smist08

September 12, 2021 at 9:32 am

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