1. Radio syntax

1.1. Radio Module

The radio module allows microbits to send messages to each other via wireless networks.

Firstly, import the radio module.

import radio: Import the radio module

from microbit import *
import radio

1.2. Radio On and Off

To send or receive messages, the radio needs to be turned on.

radio.on(): Turns the radio on.

radio.off(): Turns off the radio, thus saving power and memory.

from microbit import *
import radio

radio.on()

1.3. Radio settings

If config is not called then the defaults are used.

radio.config(length=32, queue=3, channel=7, power=6, address=0x75626974, group=0, data_rate=radio.RATE_1MBIT)

Configures various keyword based settings relating to the radio.

The length (default=32) defines the maximum length, in bytes, of a message sent via the radio. 1 character = 1 byte. It can be up to 251 bytes long (254 - 3 bytes for S0, LENGTH and S1 preamble).

The queue (default=3) specifies the number of messages that can be stored on the incoming message queue. If there are no spaces left on the queue for incoming messages, then the incoming message is dropped.

The channel (default=7) can be an integer value from 0 to 83 (inclusive) that defines an arbitrary “channel” to which the radio is tuned. Messages will be sent via this channel and only messages received via this channel will be put onto the incoming message queue. Each step is 1MHz wide, based at 2400MHz.

The power (default=6) is an integer value from 0 to 7 (inclusive) to indicate the strength of signal used when broadcasting a message. The higher the value the stronger the signal, but the more power is consumed by the device. The numbering translates to positions in the following list of dBm (decibel milliwatt) values: [-30, -20, -16, -12, -8, -4, 0, 4].

The address (default=0x75626974) is an arbitrary name, expressed as a 32-bit address, that’s used to filter incoming packets at the hardware level, keeping only those that match the address you set. The default used by other micro:bit related platforms is the default setting used here.

The group (default=0) is an 8-bit value (0-255) used with the address when filtering messages. Conceptually, “address” is like a house/office address and “group” is like the person at that address to which you want to send your message.

The data_rate (default=radio.RATE_1MBIT) indicates the speed at which data throughput takes place. Can be one of the following contants defined in the radio module : RATE_1MBIT or RATE_2MBIT.

Note

A lower data rate of of 250kbit/sec is supported in micro:bit V1, and may be possible with micro:bit V2, but it is not guaranteed to work on all devices. To access this hidden feature for compatibility with V1 pass 2 to the data_rate argument.

radio.reset(): Reset the settings to their default values for the config function.

Those working together should set the group to an integer from 0 to 255 so that only their microbits share messages.

Set the length to the maximum value if sending long messages. Lengths greater that the default may be required if sending image strings.

from microbit import *
import radio

radio.on()
radio.config(group=9, length=251)

radio.send(message): Sends a message string. This is the equivalent of send_bytes(bytes(message, 'utf8')) but with b'\x01\x00\x01' prepended to the front (to make it compatible with other platforms that target the micro:bit).

from microbit import *
import radio

radio.on()
radio.config(group=9, length=251)
radio.send('hello')

radio.receive()

Works in exactly the same way as receive_bytes but returns whatever was sent.

Currently, it’s equivalent to str(receive_bytes(), 'utf8') but with a check that the first three bytes are b'\x01\x00\x01' (to make it compatible with other platforms that may target the micro:bit). It strips the prepended bytes before converting to a string.

A ValueError exception is raised if conversion to a string fails.

from microbit import *
import radio

radio.on()
radio.config(group=9, length=251)
radio.send('hello')

while True:
    message = radio.receive()
    if message:
        display.scroll(message)

radio.send_bytes(message): Sends a message containing bytes.

radio.receive_bytes(): Receive the next incoming message on the message queue. Returns None if there are no pending messages. Messages are returned as bytes.

radio.receive_bytes_into(buffer): Receive the next incoming message on the message queue. Copies the message into buffer, trimming the end of the message if necessary. Returns None if there are no pending messages, otherwise it returns the length of the message (which might be more than the length of the buffer).

radio.receive_full()

Returns a tuple containing three values representing the next incoming message on the message queue. If there are no pending messages then None is returned.

The three values in the tuple represent:

the next incoming message on the message queue as bytes.
the RSSI (signal strength): a value between 0 (strongest) and -255 (weakest) as measured in dBm.
a microsecond timestamp: the value returned by time.ticks_us() when the message was received.

This function is useful for providing information needed for triangulation and/or triliteration with other micro:bit devices.

from microbit import *
import radio

details = radio.receive_full()
if details:
    msg, rssi, timestamp = details