BeagleBoard/GSoC/2021 Proposal/MicroPython with GreyBus for BeagleConnect Freedom

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[Wio Terminal connection to BeagleConnect Freedom using GreyBus protocol and MicroPython]

About Student: Szymon Duchniewicz
Mentors: Jason Kridner
Code: No code just yet
GSoC: GSoC entry


Submitted for review.

About you

IRC: Willmish
Github: Willmish
School: University College London
Country: United Kingdom/Poland
Primary language: Polish
Typical work hours: 8AM-5PM CET
Previous GSoC participation: I haven't participated before in GSoC but I am very intrigued by the idea of being able to work with an Open Source organization, as I always wanted to get involved with Open Source and this looks like a great place to start! Furthermore, I believe that through this project I could develop my current skill-set substantially both in software and hardware domains. As I have some previous experience in working with embedded systems such as Arduino and Rpi and programming them in Python, I thought that the idea of bringing Micropython to BeagleConnect Freedom is great and would fit my current capabilities quite well, while also posing an interesting challenge!

About your project

Project name: Micropython for BeagleConnect Freedom


The goal of this project is to establish a connection between a Wio Terminal as host and BeagleConnect Freedom via the Greybus protocol using MicroPython. This would come along with basic GPIO, I2C, SPI, PWM, ADC drivers interfacing with Zephyr RTOS via Greybus. MicroPython is a C implementation of the widely known and used Python3 language aimed specifically to run on a microcontroller. A ported MicroPython would allow for easy out-of-the-box development and prototyping with BeagleConnect Freedom, Python being an easy to learn and use language, with powerful capabilities at the same time being very concise. The drivers would be written in C as an extension and interface to MicroPython. The port itself along with additional extensions would be based on the official documentation by MicroPython for porting the language. Additionally after the MicroPython port and writing the basic drivers I could test them in practice using the supported MikroElectronika boards.


Establishing Wio Terminal to BeagleConnect Freedom connection via Greybus

The Wio Terminal is a ATSAMD51-based microcontroller with wireless connectivity over bluetooth and Wi-Fi. Therefore a connection between the Wio and BeagleConnect Freedom can be established in a number of ways: either directly by wire using I2C protocol, SPI or UART or wireless by Bluetooth. With a big range of possible connections, developers will have a number of possible design options.

The Beagle Connect Freedom can deploy its connected peripherals as well as its own GPIO pins via Greybus and would allow for establishing an easy connection through that to the Wio Terminal. This way communication between the peripherals connected to the BC Freedom (which could also be wireless) will be easily accessible from the Wio Terminal over the Greybus.

Porting MicroPython

Porting MicroPython to BeagleConnect Freedom would be quite useful as it will allow for easy development and could be useful for deploying the Greybus interfaces nicely wrapped in a Python interface for the Wio Terminal to use. Since after the port both the Wio Terminal and the BeagleConnect Freedom would be programmable in MicroPython, developing an IoT system utilising both of them would be much easier!

Before doing anything else, MicroPython itself needs to be ported to work on Zephyr RTOS and the BealgeConnect Freedom itself. A work-in-progress port for Zephyr would be the starting point for this part of the project. Ensuring that a minimal build with a simple REPL loop can be built and run on the BeagleConnect board would be the next step.

To do this, first mpconfigport.h would need to be configured to board-specific configuration. As BeagleConnect is using Zephyr, some of it can be carried over from the main port of Zephyr, but many other configs will need to be modified to CC1352P chip-specific, others such as the heap size have to be verified. CC1352P has 80kB total RAM and the current ported version requires 16kB for its heap so this value could be kept as is.

As a step-by-step explanation, the porting process will look as follows:

  • Cloning the existing Zephyr port for MicroPython
  • Testing if the port can be properly built on the BeagleConnect Freedom, if not it will have to be adapted to work properly. Alternatively a completely new port can be set up.
  • Any further configurations and edits will be done with accordance to MicroPython's guide to porting, which can be found here.
  • Further modules (in our case SPI, I2C etc. drivers) can be added by following an example shown in the guide mentioned above, which can be found here

Writing drivers

The basic drivers required by this project include GPIO, I2C, SPI, PWM and ADC, since they would allow many sensors interfacing with the BeagleConnect Freedom to be programmable and utilised via MicroPython. Additionally implementing a Bluetooth driver would be very useful and could provide a doorway for hosting BeagleConnect to communicate/control with BeagleConnect nodes and its peripherals through Greybus. As Python in general is more space and time hungry than C, and given we have limited resources on the microcontroller, it is logical to write those basic drivers in C and create MicroPython interfaces for them.

In the current port of MicroPython for Zephyr a MicroPython module machine is already implemented with some basic submodules and functionalities for I2C and GPIO. Therefore these modules would need to be extended or rewritten to be able to interface with BeagleConnect Freedom as well as additional such drivers would be implemented for SPI, PWM and ADC. The BeagleConnect Freedom uses Greybus to communicate with connected devices and deploys interfaces to them, so the approach would be to make the drivers communicate through Greybus. An implementation of such driver is described next based on a example for I2C module:

  • Initially, implementation in Zephyr RTOS for each driver has to be identified and thoroughly understood. All of these drivers (GPIO, I2C, SPI, PWM and ADC) can be found here. (Optionally Bluetooth driver could also be implemented to allow communication between a hosting BeagleConnect and BeagleConnect nodes, while also interfacing their peripherals over Greybus)
  • The implementations of those same modules but for Greybus would need to be analysed and how exactly their interfaces get deployed. They can be found here.
  • Then for I2C and GPIO the already implemented versions in the ported MicroPython for Zephyr have to be checked and rewritten if not compatible with BeagleConnect Freedom and Greybus interfaces.
  • For all other modules, a driver has to be implemented as a submodule of the machine module to interface with the Greybus interfaces/drivers. The Greybus repo along with interface definition can be found here.
  • Lastly, each driver needs to be thoroughly tested using a MikroElectronika board or by other means. This can for example entail using a simple LED to test PWM output, or connecting other I2C devices and collecting data from them.

The graph below is a visualisation of the implementation of basic drivers and their interface with MicroPython on one end, and the interfaces of connected peripherals deployed by Greybus. Visualisation of basic driver structure as submodules for MicroPython and interface with Zephyr/connected peripherals via Greybus-deployed interfaces

Below is a rough requirement list of the drivers, a short description of them and how they will interact with BeagleConnect Freedom. All these drivers will be submodules of the machine module. These requirements are based on the actual implementation of those modules in MicroPython.

GPIO Module

The GPIO driver should allow developers to manipulate and read from GPIO pins on the BeagleConnect Freedom. Actions such as setting a pin to HIGH, LOW or reading current state would be required. More detailed explanation of necessary functions and constructors can be found on MicroPythons documentation for GPIO module. As mentioned before this driver will interface with the device interface deployed by Greybus.

I2C Module

The I2C module allows for 2 wire communication using the I2C protocol. This should allow for software and hardware I2C connections, sending data over I2C, receiving data and scanning for connected devices. There already is an existing driver for Zephyr RTOS, but it would need to be rewritten to interface with the device interface deployed by Greybus. Full list of requirements for I2C can be found here.

SPI Module

The SPI module allows for 4 wire communication using the SPI protocol/interface. The driver should allow for software and hardware SPI connections, sending and receiving data over SPI. Just as all the other modules, full list of requirements for SPI driver can be found here and will interface with the device interface deployed by Greybus. If needed, Zephyr driver found here can be used as inspiration.

PWM Module

The PWM module allows for Pulse-Width modulated signals sent from GPIO pins with PWM capabilities. More information on PWM can be found here. This is not implemented in the main MicroPython library, so it will be based on the port specific implementation for ESP8266/ESP32 with documentation examples which can be found here. Similarly to previous modules it will interface with the device interface deployed by Greybus. If needed, Zephyr driver found here can be used as an inspiration.

ADC Module

The ADC module provides an interface to analog-to-digital convertors. In principle, it should allow continues voltage to be converted to a discrete, quantized value from a particular pin. Full list of requirements can be found here and will interface with the device interface deployed by Greybus. If needed, Zephyr driver found here can be used as an inspiration.

Project Deliverables

As mentioned before, the MicroPython port would be strongly desired as it would allow for easier development of IoT systems utilising both Wio Terminal and BeagleConnect Freedom, since both systems would be programmable MicroPython. This is especially true since the BC Freedom connected devices along with its own GPIOs would be available through Greybus and nicely wrapped around in Python interfaces. As the project is somewhat extensive, it is necessary to have a list of elements which will be produced as a part of the end result of the project. Here is a list of these components along with a short explanation for each one:

  • Working connection between Wio Terminal and BeagleConnect Freedom utilising Greybus.
  • Ported version of MicroPython, working on BeagleConnect Freedom with Zephyr RTOS.
  • Working and tested GPIO, I2C, SPI, PWM and ADC drivers interfacing with Zephyr RTOS via Greybus.
  • Code examples for each module, thoroughly commented for other developers to use.
  • Documentation of the drivers and the port itself.
  • REAMDE with build instructions, description of implemented modules, etc.

Possible extensions to the project/Stretch goals

CircuitPython port

After successfully completing a MicroPython port for the BeagleConnect Freedom and writing the minimal drivers, porting CircuitPython would be a good addition. Although CircuitPython is far less advanced than MicroPython, it is more newbie-friendly. This would allow beginners easier entry to the world of IoT and for experimenting with the BeagleConnect. Adafryut has a similar guide to MicroPython's for creating a new port, which can be found here. After successfully porting, the ported version can be tested using Adafruit's CircuitPython boardtest.

Adding more MicroPython modules to work with the BeagleConnect Freedom

There are many libraries (modules) implemented in the core version of MicroPython, ranging from libraries derived from original Python3 core libraries to MicroPython-specific libraries (such as machine module). Adding some of those libraries would give more possibilities when developing on BeagleConnect Freedom using MicroPython. An example would be to implement UART duplex serial communication would be a nice extension to increase the number of possible MikroElectronika devices to be used with BeagleConnect. Also adding ubluetooth library which could be used by the BeagleConnect node device. For example a Wio Terminal could communicate with a BeagleConnect as a host device and control/communicate with a BeagleConnect node device with some peripherals connect over bluetooth, while also having their interfaces deployed by GreyBus. Since all other modules would be implemented to interface with other devices through Greybus, they could be also controlled wireless through Bluetooth!


Date Milestone Action Items
13.04.21-17.05.21 Pre-work
07.06.21 Coding Start!
  • Introductory YouTube video
  • Setup Zephyr environment on BeagleConnect Freedom along with a Greybus.
  • Experiment with BeagleConnect Freedom as well as the Wio Terminal
14.06.21 Milestone #1
  • Establish a connection via Greybus between Wio Terminal and BeagleConnect Freedom.
  • Test the connection with simple GPIO manipulation.
  • Document the progress in a first blog post
21.07.21 Milestone #2
  • Complete the MicroPython port.
  • Test minimal MicroPython port REPL.
  • Documentation for Wio Terminal-BC Freedom connection and MicroPython port.
28.06.21 Milestone #3
  • Complete the I2C module
  • Test the I2C module by connecting to Wio Terminal+Additional tests.
  • Complete the SPI module (1/2)
5.07.21 Milestone #4
  • Complete the SPI module (2/2)
  • Test the SPI module by establishing a connection to Wio Terminal.
  • Test SPI module individually with MikroElectronika peripherals/other devices on BC Freedom.
  • Complete the PWM module
  • Test the PWM module individually with MikroElectronika peripherals/other devices on BC Freedom
12.07.21 Milestone #5
  • Complete the ADC module
  • Test the ADC module individually with MikroElectronika peripherals/other devices on BC Freedom.
  • Evaluate the mentor
  • Document the progress in a blog post
19.07.21 Milestone #6
  • Polish the current MicroPython port
  • Polish each module and retest
  • Write Documentation for each of the modules, add examples for each module
26.07.21 Milestone #7
  • Implement extensions to the project:
  • Add more MicroPython modules to work with BeagleConnect Freedom (e.g. ubluetooth)
  • Test bluetooth module by establishing connection between Wio Terminal and BC Freedom.
  • Write Documentation for the newly added module
14.08.21 Milestone #8
  • Implement extensions to the project:
  • Port CircuitPython to BeagleConnect Freedom
  • Test the ported CircuitPython
  • Create short documentation for the ported CircuitPython
  • Document the progress in a blog post
  • Record completion YouTube video
24.08.21 Feedback time
  • Complete feedback form for the mentor
31.08.21 Results announced

Experience and approach

I am currently a first year Computer Science student, but Programming, Electronics and Computer Science in general is a hobby of mine for many years now. I have managed to create a few project and gain a lot of experience since then. Some of my knowledge of C I have gained while working on a project developing a simple Shell in C, which can be found here. The project encouraged me to dive deeper into the inner workings of a Shell as well as a REPL loop, while also gaining valuable knowledge of Linux in general.

Additionally I have a strong knowledge base of Python, as it was one of my first languages to ever learn and I completed multiple projects involving this technology. The projects worth mentioning here include a Sorting Algorithm Complexity Analysis Tool (SACAT), whose first prototype me and my colleagues from university recently have finished. The project can be found here along with a extensive report/proposal of that project. Main principle of it is to give a simple-to-use tool which given any sorting algorithm can estimate and display its time and space complexity, as well as test the algorithms correctness. Another interesting project was actually part of my end-of-high school examination and involved creating an IDE for statically typed Python, with type checking and can be found here, though it is a prototype with limited capabilities.

Furthermore I have done some small contributions to open source projects such as Raspberry Pis docs and even though it was just a small change it showed me that everyone can contribute to such projects. I would like to continue contributing to such open source projects (though maybe this time in slightly bigger contributions!).

I have previous experience with microcontrollers and embedded systems such as Ardunio, Raspberry Pi and STM32, starting from a project I completed 4 years ago based on Arduino Micro for a follow liner robot with colour sensors, a brief presentation explaining its design process and some videos of it in action can be found here. Along with my brothers I have also taken part in and completed element14's design challenge: 1 meter of pi, during which we have created a prototype of a gardening drawer that fits under your bed - Envidrawer. More information on that project can be found on our blogs here.

I also have a lot of experience in 3D printing (as well as fixing them, as most of 3D printer users probably do :D!) and all parts used in my electronics projects are designed and 3D printed by me! Samples of that can be found in the Envidrawer project linked above.


Since the project requires mostly individual work on the project, I will make sure to get in touch with the BeagleBoard community to get feedback/help from more experienced developers if my mentor is not available. It is crucial to remain calm when a big obstacle is met in project development and I so keeping that in mind I will look for alternative solutions to the problem. Additionally there is plenty of information to help me out already available in MicroPython documentation as to how porting should be done and many examples of already complete ports on MicroPython's github. If taking the above into consideration I still do not find the answer, I can ask on relevant subreddits for help as there are other smart people who may know the solution to my problem :).

Also I could look at the already ported versions of MicroPython and their implementation of all those drivers.


Below are some quotes from the BeagleBoard community regarding the proposal as well as stretch goals mentioned.

 Doing a Micropython Greybus host would be great. 
 Doing it on the Wio Terminal has been a thought. 
 So, Freedom is a Greybus device and Wio Terminal would access the peripherals over Greybus over BLE.


 I believe Wio Terminal is a pretty cool device and it would be great to see it connect to BeagleConnect Freedom to access the peripherals over Greybus over Bluetooth.



Pull request required for qualification can be found here.