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--- en:edu:zmitac:s2:iotn:ble1 [2023/12/16 14:16] – [Variables and objects definition] ktokarz
+++ en:edu:zmitac:s2:iotn:ble1 [2023/12/17 19:57] (current) – [Bluetooth Low Energy for STM32 - peripheral] ktokarz
@@ Line 1: / Line 1: @@
-====== Bluetooth Low Energy for STM32 - peripheral ======
+====== Bluetooth Low Energy for STM32 - peripheral write ======
 This laboratory shows the details of the example provided as part of the STM32duinoBLE library by Arduino.
 ===== Installing the library and importing the example =====
@@ Line 29: / Line 29: @@
 BLEByteCharacteristic switchCharacteristic("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);
 </code>
-The number of characteristics in one service is limited to 512 by BLE specification. You can experiment on how many characteristics can be used in Arduino implementation.\\
+The characteristic defined in the example allows remote devices to read or write byte values. It is also possible to define characteristics which contain the text string.
+<code>
+BLECharacteristic textCharacteristic("19B10001-E8F2-537E-4F6C-D104768A1215",  BLERead | BLEWrite, "sample text");
+</code>
+In the BLE specification, the maximal length of the characteristic's value is 512 bytes, the number of characteristics in one service is also limited to 512. You can experiment on how many characteristics can be used in Arduino implementation.\\
 The example program allows the remote device to control the state of the LED, so there is also a declaration of the "ledPin" variable.
 <code>
@@ Line 68: / Line 72: @@
   // start advertising
   BLE.advertise();
+</code>
+Also LED output is initialized in the setup() function.
+<code>
+  // set LED pin to output mode
+  pinMode(ledPin, OUTPUT);
 </code>
 ==== Loop function ====
@@ Line 75: / Line 84: @@
 </code>
 <note>BLE.central() function is non-blocking so you can execute other code if the connection is not established.</note>
-To check if there is an active connection the state of "central" variable can be checked. While it is not NULL the program prints the MAC address of the remote device and jumps into the while loop to handle write events requested by the central device. In the example value "0" turns the LED off, while the other value sets the LED on.\\
+To check if there is an active connection the state of "central" variable can be checked. While it is not NULL the program prints the MAC address of the remote device and jumps into the while loop to handle write events requested by the central device. The while loop is executed until the remote device decides to close the connection. If the remote device writes a new value to the characteristic, the "written" property signals this situation. While it is TRUE we can read the value. In the example value "0" turns the LED off, while the other value sets the LED on.\\
-The while loop is executed until the remote device decides to close the connection.
 <code>
 // if a central is connected to peripheral:
@@ Line 104: / Line 113: @@
   }
 </code>
+<note>F("text") used in the Serial.print() function means that the text will be always taken directly from Flash memory. It frees some of the RAM during the program execution.</note>
+===== Tasks to do during the laboratory =====
+  - Import the Arduino blink example.
+  - Add STM32duinoBLE library to the project.
+  - Replace the original blink code with the LED example, compile and execute.
+  - Add characteristics to existing service for controlling other LEDs on the Nucleo board.
+  - Add service and the characteristic to display texts (using serial port).
+Reading text value can be done with memcpy() function.
+<code>
+char buffer[10];
+memcpy(buffer, textcharacteristic.value(), textcharacteristic.valueLength());
+</code>
+<note>Nucleo board has three LEDs: red, green, and blue named LED_RED, LED_GREEN, and LED_BLUE. The blue LED is also named LED_BUILTIN or LED1, the green LED is also named LED2, and the red LED is also named LED3.</note>