Microcontroller programming with BBC micro:bit
MicroPython Commands
Table 2 lists the most important MicroPython commands for communicating with the micro:bit's sensors. There are commands for the matrix display (Figure 4), the buttons, and the digital input and output.
Table 2
micro:bit Commands
Function | Effect |
---|---|
microbit.display.show(Image.HAPPY) |
Displays a smiley face on the LED matrix |
microbit.display.show(Image.SAD) |
Displays a frowning face on the LED matrix |
microbit.display.set_pixel(1, 2, 9) |
Switches the LED at position (1,2) to maximum brightness |
microbit.button_a.is_pressed() |
Checks whether button a is pressed |
microbit.button_a.was_pressed() |
Checks whether the button was pressed after switching on, or the last request |
microbit.button_a.get_presses() |
Counts how many times the button was pressed after the last request |
microbit.accelerometer.get_x() |
Reads the x-coordinates of the position sensor |
microbit.pin0.read_digital() |
Reads the digital input at pin 0 |
microbit.pin0.write_digital(1) |
Sets the digital input at pin 0 |
music.play(music.RINGTONE) |
Plays a tune if a speaker is connected to pin 0 |
The command is always preceded by the name of the matching MicroPython library. |

The acceleration sensor also serves as a position sensor when the module is at rest. In order not to have to deal with the orientation angles of its three axes, there is the microbit.accelerometer.current_gesture()
command. It understands the orientations up
, down
, left
, right
, face up
, face down
, and shake
.
A magnetometer with three axes is also available. In theory, it is sensitive enough to detect the direction of the Earth's magnetic field – in practice, it is difficult to do so. The temperature sensor is similar: It also measures the processor temperature. However, under no circumstances should you heat up the board with a hair dryer – be content with measuring the ambient temperature.
The microbin.pin0.is_touched()
command connects the digital input via a 10m ohm pull-up resistor. The micro:bit uses this to detect if there is too high of a resistance to ground. Typically, one finger is sufficient for this, while another finger simultaneously touches the micro:bit's ground cable (GND, the large contact at bottom right on the board).
Interface
Once flashed, the microcontroller no longer accepts commands. Instead, it switches to communication and outputs its information serially via the USB connection. In Figure 5, the connected micro:bit passes the brightness value to Mu's REPL command window via the print()
command. If you close the program, you get direct access to the data.
You already know the device name for the serial interface, in our case ttyACM3
, as shown in Listing 1. The commands in Listing 4 redirect the micro:bit's output to the terminal window. The cat
command returns the brightness value as a decimal number; od -x
returns it as a hexadecimal number (Figure 6).
Listing 4
Redirecting Output to the Terminal
$ cat /dev/ttyACM3 $ od -x < /dev/ttyACM3
Hex Files
The Mu editor converts the program code into a hex file. If you disconnect the micro:bit before flashing, the Mu editor enables access to the file and asks where to store it.
The hex file consists of an 8KB MicroPython interpreter. MicroPython is a reduced Python instruction set, which feels like real Python in its basic functions. Additionally, the file contains the program's byte sequence, which the MicroPython interpreter then executes. Finally, the hex file contains a compressed version of the actual program text including comments.
Contrary to what the name might suggest, the hex file is initially a text file: The address and bytes are written out as text (Listing 5). The file therefore shrinks as soon as the system converts the ASCII text into binary numbers. This explains why a hex file of more than 500KB fits into the micro:bit's memory, which has a capacity of 256KB – including the Micropython interpreter. In the end there are about 8KB of physical memory for your own python scripts.
Listing 5
Sample Hex File
:020000040000FA :1000000000400020218E01005D8E01005F8E010006 :1000100000000000000000000000000000000000E0 [...]
Flashing the micro:bit via a connected computer is a more elegant solution. The micro:bit logs on to the computer's filesystem as a USB stick, so you just need to copy the hex file to it. If the micro:bit recognizes the format, it converts the content into a byte sequence and immediately writes it to its flash memory. Otherwise, the file remains in USB memory, just like on a normal memory stick.
Although flashing always overwrites the old data, the data is retained when the power supply is disconnected. The micro:bit executes the program once it has been loaded, as soon as you resupply power.
« Previous 1 2 3 Next »
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you've found an article to be beneficial.
News
-
Linux Kernel Reducing Long-Term Support
LTS support for the Linux kernel is about to undergo some serious changes that will have a considerable impact on the future.
-
Fedora 39 Beta is Now Available for Testing
For fans and users of Fedora Linux, the first beta of release 39 is now available, which is a minor upgrade but does include GNOME 45.
-
Fedora Linux 40 to Drop X11 for KDE Plasma
When Fedora 40 arrives in 2024, there will be a few big changes coming, especially for the KDE Plasma option.
-
Real-Time Ubuntu Available in AWS Marketplace
Anyone looking for a Linux distribution for real-time processing could do a whole lot worse than Real-Time Ubuntu.
-
KSMBD Finally Reaches a Stable State
For those who've been looking forward to the first release of KSMBD, after two years it's no longer considered experimental.
-
Nitrux 3.0.0 Has Been Released
The latest version of Nitrux brings plenty of innovation and fresh apps to the table.
-
Linux From Scratch 12.0 Now Available
If you're looking to roll your own Linux distribution, the latest version of Linux From Scratch is now available with plenty of updates.
-
Linux Kernel 6.5 Has Been Released
The newest Linux kernel, version 6.5, now includes initial support for two very exciting features.
-
UbuntuDDE 23.04 Now Available
A new version of the UbuntuDDE remix has finally arrived with all the updates from the Deepin desktop and everything that comes with the Ubuntu 23.04 base.
-
Star Labs Reveals a New Surface-Like Linux Tablet
If you've ever wanted a tablet that rivals the MS Surface, you're in luck as Star Labs has created such a device.