micro:bit Micropython API¶
The microbit module¶
Everything directly related to interacting with the hardware lives in the microbit module. For ease of use it’s recommended you start all scripts with:
from microbit import *
The following documentation assumes you have done this.
There are a few functions available directly:
# sleep for the given number of milliseconds. sleep(ms) # returns the number of milliseconds since the micro:bit was last switched on. running_time() # makes the micro:bit enter panic mode (this usually happens when the DAL runs # out of memory, and causes a sad face to be drawn on the display). The error # code can be any arbitrary integer value. panic(error_code) # resets the micro:bit. reset()
The rest of the functionality is provided by objects and classes in the microbit module, as described below.
Note that the API exposes integers only (ie no floats are needed, but they may be accepted). We thus use milliseconds for the standard time unit.
You can see a list of all available modules by writing
help('modules') in the REPL.
The LED display¶
The LED display is exposed via the display object:
# gets the brightness of the pixel (x,y). Brightness can be from 0 (the pixel # is off) to 9 (the pixel is at maximum brightness). display.get_pixel(x, y) # sets the brightness of the pixel (x,y) to val (between 0 [off] and 9 [max # brightness], inclusive). display.set_pixel(x, y, val) # clears the display. display.clear() # shows the image. display.show(image, delay=0, wait=True, loop=False, clear=False) # shows each image or letter in the iterable, with delay ms. in between each. display.show(iterable, delay=400, wait=True, loop=False, clear=False) # scrolls a string across the display (more exciting than display.show for # written messages). display.scroll(string, delay=400)
Provide digital and analog input and output functionality, for the pins in the connector. Some pins are connected internally to the I/O that drives the LED matrix and the buttons.
Each pin is provided as an object directly in the
microbit module. This keeps the API relatively flat, making it very easy to use:
- Warning: P17-P18 (inclusive) are unavailable.
Each of these pins are instances of the
MicroBitPin class, which offers the following API:
# value can be 0, 1, False, True pin.write_digital(value) # returns either 1 or 0 pin.read_digital() # value is between 0 and 1023 pin.write_analog(value) # returns an integer between 0 and 1023 pin.read_analog() # sets the period of the PWM output of the pin in milliseconds # (see https://en.wikipedia.org/wiki/Pulse-width_modulation) pin.set_analog_period(int) # sets the period of the PWM output of the pin in microseconds # (see https://en.wikipedia.org/wiki/Pulse-width_modulation) pin.set_analog_period_microseconds(int) # returns boolean pin.is_touched()
You don’t always need to create one of these yourself - you can access the image shown on the display directly with display.image. display.image is just an instance of Image, so you can use all of the same methods.
# creates an empty 5x5 image image = Image() # create an image from a string - each character in the string represents an # LED - 0 (or space) is off and 9 is maximum brightness. The colon ":" # indicates the end of a line. image = Image('90009:09090:00900:09090:90009:') # create an empty image of given size image = Image(width, height) # initialises an Image with the specified width and height. The buffer # should be an array of length width * height image = Image(width, height, buffer) # methods # returns the image's width (most often 5) image.width() # returns the image's height (most often 5) image.height() # sets the pixel at the specified position (between 0 and 9). May fail for # constant images. image.set_pixel(x, y, value) # gets the pixel at the specified position (between 0 and 9) image.get_pixel(x, y) # returns a new image created by shifting the picture left 'n' times. image.shift_left(n) # returns a new image created by shifting the picture right 'n' times. image.shift_right(n) # returns a new image created by shifting the picture up 'n' times. image.shift_up(n) # returns a new image created by shifting the picture down 'n' times. image.shift_down(n) # get a compact string representation of the image repr(image) # get a more readable string representation of the image str(image) #operators # returns a new image created by superimposing the two images image + image # returns a new image created by multiplying the brightness of each pixel by n image * n # built-in images. Image.HEART Image.HEART_SMALL Image.HAPPY Image.SMILE Image.SAD Image.CONFUSED Image.ANGRY Image.ASLEEP Image.SURPRISED Image.SILLY Image.FABULOUS Image.MEH Image.YES Image.NO Image.CLOCK12 # clock at 12 o' clock Image.CLOCK11 ... # many clocks (Image.CLOCKn) Image.CLOCK1 # clock at 1 o'clock Image.ARROW_N ... # arrows pointing N, NE, E, SE, S, SW, W, NW (microbit.Image.ARROW_direction) Image.ARROW_NW Image.TRIANGLE Image.TRIANGLE_LEFT Image.CHESSBOARD Image.DIAMOND Image.DIAMOND_SMALL Image.SQUARE Image.SQUARE_SMALL Image.RABBIT Image.COW Image.MUSIC_CROTCHET Image.MUSIC_QUAVER Image.MUSIC_QUAVERS Image.PITCHFORK Image.XMAS Image.PACMAN Image.TARGET Image.TSHIRT Image.ROLLERSKATE Image.DUCK Image.HOUSE Image.TORTOISE Image.BUTTERFLY Image.STICKFIGURE Image.GHOST Image.SWORD Image.GIRAFFE Image.SKULL Image.UMBRELLA Image.SNAKE # built-in lists - useful for animations, e.g. display.show(Image.ALL_CLOCKS) Image.ALL_CLOCKS Image.ALL_ARROWS
The accelerometer is accessed via the
# read the X axis of the device. Measured in milli-g. accelerometer.get_x() # read the Y axis of the device. Measured in milli-g. accelerometer.get_y() # read the Z axis of the device. Measured in milli-g. accelerometer.get_z() # get tuple of all three X, Y and Z readings (listed in that order). accelerometer.get_values() # return the name of the current gesture. accelerometer.current_gesture() # return True or False to indicate if the named gesture is currently active. accelerometer.is_gesture(name) # return True or False to indicate if the named gesture was active since the # last call. accelerometer.was_gesture(name) # return a tuple of the gesture history. The most recent is listed last. accelerometer.get_gestures()
The recognised gestures are:
The compass is accessed via the compass object:
# calibrate the compass (this is needed to get accurate readings). compass.calibrate() # return a numeric indication of degrees offset from "north". compass.heading() # return an numeric indication of the strength of magnetic field around # the micro:bit. compass.get_field_strength() # returns True or False to indicate if the compass is calibrated. compass.is_calibrated() # resets the compass to a pre-calibration state. compass.clear_calibration()
There is an I2C bus on the micro:bit that is exposed via the i2c object. It has the following methods:
# read n bytes from device with addr; repeat=True means a stop bit won't # be sent. i2c.read(addr, n, repeat=False) # write buf to device with addr; repeat=True means a stop bit won't be sent. i2c.write(addr, buf, repeat=False)
uart to communicate with a serial device connected to the device’s I/O pins:
# set up communication (use pins 0 [TX] and 1 [RX]) with a baud rate of 9600. uart.init() # return True or False to indicate if there are incoming characters waiting to # be read. uart.any() # return (read) n incoming characters. uart.read(n) # return (read) as much incoming data as possible. uart.read() # return (read) all the characters to a newline character is reached. uart.readline() # read bytes into the referenced buffer. uart.readinto(buffer) # write bytes from the buffer to the connected device. uart.write(buffer)