uBit.serial

Serial communication provides a simple way to exchange a series of bytes between one computer and another. The runtime’s implementation of serial is general purpose and supports a number of different modes. It has a circular buffer for both the reception and transmission of data, and provides notifications to the user through the MessageBus.

By default, the baud rate for MicroBitSerial is 115200 and has very little overhead up until it is used to send() or read(), at which point buffers are allocated in order to accommodate incoming or outgoing data.

MicroBitSerial inherits from mbeds’ [RawSerial](https://developer.mbed.org/users/mbed_official/code/mbed/docs/252557024ec3/classmbed_1_1RawSerial.html) class, which exposes a lightweight version of printf() and incurs minimal overhead as MicroBitSerial’s buffers will not be allocated.

The MicroBitSerial class supports multithreaded operation, ensuring that only one fiber can access the Serial port at a time.

The USB interface on the micro:bit is the [KL26Z](https://www.mbed.com/en/development/hardware/prototyping-production/daplink/daplink-on-kl26z/#Updating_your_DAPLink_firmware).

Note

On Mac OSX and Linux Serial communication works out of the box, however on Windows an additional [driver](https://developer.mbed.org/handbook/Windows-serial-configuration) is required.

Warning

The baud rate is shared across all instances of MicroBitSerial (this is enforced in hardware).

Serial Modes

There are three modes of operation for all send() or read() calls:

ASYNC

Returns immediately after fetching any available data for a given call

SYNC_SPINWAIT

Synchronously access the serial port until the selected operation is complete. This mode will lock up the processor, and isn’t recommended if multiple fibers are in use.

SYNC_SLEEP

Blocks the current fiber until the selected operation is complete. This mode cooperates with the Fiber scheduler, and should be used in a multi-fiber program.

Serial Debug

In MicroBitConfig.h, the configuration option MICROBIT_DEBUG can be used to activate serial debugging for many of the components in the runtime.