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tags:physical-computing microbit makecode

hardware overview:
https://tech.microbit.org/hardware

Main MCU: Nordic Semiconductor nRF52833 (v2), nRF51822 (v1)
nRF52833: Arm Cortex-M4 32 bit, 64MHz, 512KB Flash, 128KB RAM
nRF51822: Arm Cortex-M0 32 bit, 16MHz, 256KB Flash, 16KB RAM
Interface MCU: Nordic nRF52833 or nRF52820 (v2.2), Freescale KL27 (v2), KL26 (v1)

Excellent list of resources for micro:bit: https://github.com/carlosperate/awesome-microbit

Power

Supply

https://tech.microbit.org/hardware/powersupply/

the microbit can be powered by:

• 3-5V via usb micro connector
• 3V via JST connector (connects directly to VCC on v1 board. on v2 passes through the regulator, and so should be 5V tolerant?)
• 3V via '3V' and 'GND' pins on Edge connector, or the two rectangular padas on rear right edge of board.

VCC is min 1.7 max 3.6V

On v1 board should not connect a lipo battery to the JST connector as the voltage will likely exceed the 3.6V vcc max.

Consumption

KL26's on chip regulator on v1 board provides 120mA. NCP114BMX330TCG Regulator on v2 board provides 300mA.

Board with all on-board peripherals in use consumes max 30mA

Sleep mode

v2 board only
https://support.microbit.org/support/solutions/articles/19000120358-how-do-i-power-off-or-put-the-micro-bit-to-sleep-

• press and hold power/reset for 5 seconds
• if powered by usb, will enter 'sleep' mode
• if powered by battery or external power, will power off
• press reset to wake/power-on

Programming

Programming is done by copying a hex file into the virtual external drive created by the microbit.

In Chrome or Edge webUSB can be used to connect directly to a web app to the board to program it or open a serial connection.

MakeCode

https://makecode.microbit.org/
https://makecode.com/about
Programming by blocks, javascript or python. Can create projects that are python/javascript-only, or use a mixed project to permit interchanging between languages.

MakeCode is based on the Microsoft Programming Experience Toolkit (PXT).
https://github.com/microsoft/pxt

There are various versions of MakeCode for other "targets" such as the Adafruit Circuit Playground: https://makecode.adafruit.com
and a variety of other boards and platforms:
https://maker.makecode.com/
https://makecode.com/labs

Code in MakeCode is converted to Static TypeScript. When downloading the code it is converted to the target's native format and can be saved as a hex file. (in the case of the microbit, maybe this is in C/C++ for interpretation by the the DAL/CODAL rutnime? see https://tech.microbit.org/software/runtime/)

MakeCode Python is not compatible with MicroPython, it is tailored to MakeCode and has a different API ("It is in fact just static TypeScript surfaced with Python syntax")
https://support.microbit.org/support/solutions/articles/19000111744-makecode-python-and-micropython

Command Line Tool

PXT can be used via the commandline using node.js
https://makecode.com/cli

MicroPython

Can program the microbit directly with MicroPython
https://github.com/bbcmicrobit/micropython
https://microbit-micropython.readthedocs.io/en/v2-docs/

Using the microbit web Python Editor, wich also supports webUSB
https://python.microbit.org/v/2
https://github.com/bbcmicrobit/PythonEditor

Can also use the Mu desktop Python Editor
https://codewith.mu/en/

Can also use the REPL (Read, Evaluate, Print Loop) via either editor, or via a serial connection in such as with PuTTY, or screen

CircuitPython

CircuitPython is a version of MicroPython developed by Adafruit primarily for the SAMD21 boards but with some added features.
https://learn.adafruit.com/welcome-to-circuitpython/overview

Using CircuitPython on the microbit requires updating the firmware first:
https://circuitpython.org/board/microbit_v2/

Arduino

It is possible to use the Arduino IDE with the microbit
https://learn.adafruit.com/use-micro-bit-with-arduino/install-board-and-blink

Firmware

The microbit has an interface MCU that provides:

• MSC - USB mass storage device for drag-and-drop programming of the target MCU’s flash memory
• CDC - serial pass-through from the target MCU to the PC.
• HID - CMSIS-DAP compliant debug channel
• WebUSB

https://microbit.org/get-started/user-guide/firmware/
https://tech.microbit.org/software/daplink-interface/

The microbit can boot in two ways:

• interface mode, appears as the external drive MICROBIT - hex files are written to the target MCU flash
• bootloader mode, appears as the external drive MAINTENANCE - hex files are written to the interface MCU flash (in this case, the hex file must contain a DAPLink image)
  • this will update the DAPLink firmware but not the bootloader on the interface MCU. If there is an issue with the bootloader, a full DAPlink image can be flashed onto the interface chip via another bootloader mode (https://tech.microbit.org/software/daplink-interface/#updating-the-daplink-full-image)

DAPLink

Interface software for programming and debugging software on arm cortex cpus.
https://daplink.io/
https://github.com/ARMmbed/DAPLink

Nice quick overview by ladyada about SWD, how it is different from SPI, and how they developed adafruit_DAP for flashing the SAMD chips on their boards:
https://www.youtube.com/watch?v=bzihf4l7joc
https://github.com/adafruit/Adafruit_DAP

Wireless

Supports Bluetooth 5.1 with Bluetooth Low Energy(BLE)
https://tech.microbit.org/bluetooth/

There is also a microbit-radio protocol that uses other standards provided by the Nordic chip. This is the protocol used by the default Radio functions in MakeCode, and provides a simpler way to send messages between microbits.
https://support.microbit.org/support/solutions/articles/19000083637-using-the-micro-bit-wirelessly-
https://lancaster-university.github.io/microbit-docs/ubit/radio/

In order to use bluetooth function in MakeCode, an extension needs to be added and it will remove the default Radio functions.

Introduction to networking, using the microbit-radio protocol:
https://microbit.nominetresearch.uk/networking-book-online/