adding missing writeline function (#1667)

* adding missing writeline function

* 1.2.12

docs/reference/bluetooth.md

@@ -27,6 +27,7 @@ bluetooth.setTransmitPower(7);
 ```cards
 bluetooth.startUartService();
 bluetooth.uartReadUntil("");
+bluetooth.uartWriteLine("");
 bluetooth.uartWriteString("");
 bluetooth.uartWriteNumber(0);
 bluetooth.uartWriteValue("", 0);
@@ -50,6 +51,7 @@ For more advanced information on the @boardname@ Bluetooth UART service includin
 [startAccelerometerService](/reference/bluetooth/start-accelerometer-service), [startButtonService](/reference/bluetooth/start-button-service), [startIOPinService](/reference/bluetooth/start-io-pin-service), [startLEDService](/reference/bluetooth/start-led-service), [startMagnetometerService](/reference/bluetooth/start-magnetometer-service), [startTemperatureService](/reference/bluetooth/start-temperature-service), 
 [startUartService](/reference/bluetooth/start-uart-service),
 [uartReadUntil](/reference/bluetooth/uart-read-until), 
+[uartWriteLine](/reference/bluetooth/uart-write-line), 
 [uartWriteString](/reference/bluetooth/uart-write-string), 
 [uartWriteNumber](/reference/bluetooth/uart-write-number), 
 [uartWriteValue](/reference/bluetooth/uart-write-value), 

docs/reference/bluetooth/uart-write-line.md

@@ -0,0 +1,51 @@
+# UART Write Line
+
+## ~hint
+![](/static/bluetooth/Bluetooth_SIG.png)
+
+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.
+
+## ~
+
+The [Bluetooth UART service](/reference/bluetooth/start-uart-service) allows another device such as a smartphone to exchange any data it wants to with the @boardname@, in small chunks. 
+
+With the Bluetooth UART service running, this block allows a @boardname@ to send a line of text to a Bluetooth connected device.
+
+```sig
+bluetooth.uartWriteLine("");
+```
+
+## Example: Starting the Bluetooth UART service and then sending "HELLO" whenever button A is pressed and another device has connected over Bluetooth
+
+```blocks
+let connected = 0;
+bluetooth.onBluetoothConnected(() => {
+    basic.showString("C");
+    connected = 1;
+});
+bluetooth.onBluetoothDisconnected(() => {
+    basic.showString("D");
+    connected = 0;
+});
+input.onButtonPressed(Button.A, () => {
+    if (connected == 1) {
+        bluetooth.uartWriteLine("HELLO");
+    }
+});
+```
+
+## Video - UART service guessing game
+
+https://www.youtube.com/watch?v=PgGeWddMAZ0
+
+## Advanced
+ 
+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/)
+
+## See also
+
+[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)
+
+```package
+bluetooth
+```

libs/bluetooth/bluetooth.ts

@@ -24,6 +24,16 @@ namespace bluetooth {
         console.log("UART Write: " + data)
     }
 
+    /**
+    *  Writes to the Bluetooth UART service buffer. From there the data is transmitted over Bluetooth to a connected device.
+    */
+    //% help=bluetooth/uart-write-line weight=79
+    //% blockId=bluetooth_uart_line block="bluetooth uart|write line %data" blockGap=8
+    //% parts="bluetooth" advanced=true
+    export function uartWriteLine(data: string): void {
+        uartWriteString(data + "\r\n");
+    }
+
     /**
      * Prints a numeric value to the serial
      */