ustruct

The ustruct module in MicroPython is used to pack and unpack primitive data types.

This module is particularly useful for handling binary data and interfacing with hardware that expects data in specific formats.

see: https://docs.micropython.org/en/latest/library/struct.html

ustruct.calcsize(fmt)

Return the number of bytes needed to store the given fmt.

ustruct.pack(fmt, v1, v2, ...)

Pack the values v1, v2, … according to the format string fmt. The return value is a bytes object encoding the values.

ustruct.pack_into(fmt, buffer, offset, v1, v2, ...)

Pack the values v1, v2, … according to the format string fmt into a buffer starting at offset. offset may be negative to count from the end of buffer.

ustruct.unpack(fmt, data)

Unpack from the data according to the format string fmt. The return value is a tuple of the unpacked values.

ustruct.unpack_from(fmt, data, offset=0, /)

Unpack from the data starting at offset according to the format string fmt. offset may be negative to count from the end of data. The return value is a tuple of the unpacked values.

Pack and unpack

---

from microbit import *
import ustruct

# Pack data
packed_data = ustruct.pack('hhl', 1, 2, 3)
print(packed_data)  # Output: b'\x01\x00\x02\x00\x03\x00\x00\x00'

# Unpack data
unpacked_data = ustruct.unpack('hhl', packed_data)
print(unpacked_data)  # Output: (1, 2, 3)

---

Radio send and receive bytes

There are two microbits communicating via radio.

Send accelerometer data from one microbit to another.

Using ustruct.pack ensures the data is sent in a compact binary format.

Using ustruct.unpack to convert the data back.

Sender code:

from microbit import *
import radio
import ustruct

radio.on()

while True:
    x = accelerometer.get_x()
    y = accelerometer.get_y()
    z = accelerometer.get_z()
    # Pack the data into a binary format
    packed_data = ustruct.pack('>hhh', x, y, z)
    # Send the packed data over radio
    radio.send_bytes(packed_data)

    sleep(1000)

Receiver code:

from microbit import *
import radio
import ustruct

radio.on()

while True:
    incoming = radio.receive_bytes()
    if incoming:
        # Unpack the received binary data
        x, y, z = ustruct.unpack('>hhh', incoming)
        # Display the unpacked data
        display.scroll("X:{} Y:{} Z:{}".format(x, y, z), delay=80)