45 lines
3.3 KiB
Markdown
Executable File
45 lines
3.3 KiB
Markdown
Executable File
# Bluetooth UART Service
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### ~hint
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For another device like a smartphone to use any of the Bluetooth "services" which the @boardname@ has, it must first be [paired with the @boardname@](/reference/bluetooth/bluetooth-pairing). Once paired, the other device may connect to the @boardname@ and exchange data relating to many of the @boardname@'s features.
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### ~
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The Bluetooth UART service allows another device such as a smartphone to exchange any data it wants to with the @boardname@, in small chunks which are intended to be joined together. [UART[(https://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter) stands for Universal Asynchronous Receiver Transmitter and is one way in which serial data communications can be performed, usually between two devices connected by a physical, wired connection. The Bluetooth UART service emulates the behaviour of a physical UART system and allows the exchange of a maximum of 20 bytes of data at a time in either direction.
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When this service is used, the @boardname@ sets up a 60 byte buffer and data it receives will be accumulated in the buffer until it is full. When using the UART service from your @boardname@ code, you can indicate a special character which will be used to mean that the entire message in at most three chunks has now been sent by the other, connected device, at which point the @boardname@ will release the entire contents of its buffer to any code trying to read it. In other words this special character, known as a 'delimiter' is used by the device connected to the @boardname@ to mean "I've sent my whole message, you can now use it".
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You could use the UART service for many things. It doesn't care what you put in messages which makes it very flexible. You could create a guessing game, with questions and answers passing between @boardname@ and a smartphone or you could connect a camera to the @boardname@ and transmit image data obtained from the edge connector, in chunks over Bluetooth to a smartphone. There are a great many possibilities.
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To use the Bluetooth UART service from another device you'll need additional @boardname@ code which reads and uses data from the UART buffer and / or writes data to the buffer for transmission over Bluetooth to another device.
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```sig
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bluetooth.startUartService();
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```
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### Example: Starting the Bluetooth UART service
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The following code shows the Bluetooth UART service being started:
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```blocks
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bluetooth.startUartService();
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```
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### Video - UART service guessing game
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https://www.youtube.com/watch?v=PgGeWddMAZ0
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### Advanced
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For more advanced information on the @boardname@ Bluetooth UART service including information on using a smartphone, see the [Lancaster University @boardname@ runtime technical documentation](http://lancaster-university.github.io/microbit-docs/ble/uart-service/)
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### See also
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[About Bluetooth](/reference/bluetooth/about-bluetooth), [@boardname@ Bluetooth profile overview ](http://lancaster-university.github.io/microbit-docs/ble/profile/), [@boardname@ Bluetooth profile reference](http://lancaster-university.github.io/microbit-docs/resources/bluetooth/microbit-profile-V1.9-Level-2.pdf), [Bluetooth on @boardname@ resources](http://bluetooth-mdw.blogspot.co.uk/p/bbc-microbit.html), [Bluetooth SIG](https://www.bluetooth.com)
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```package
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bluetooth
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```
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