To send and receive data between the UART and BLE connection, Nordic UART Service (NUS) is used. So, on a Arduino Nano BLE 33, if we want to receive data over Bluetooth from mobile phone and print the same over UART, this service has to be used. NUS acts a bridge between the serial port and wireless section.
Mobile Phone is a Central device which connects to the Peripheral which is a Nordic board here. The Nordic board advertises continuously and then waits for the connection to Central device. The advertising happens on the 3 advertising channels that are out of 40 channels.
Below is the code for receiving data from BLE and printing over UART
#include <ArduinoBLE.h>
BLEService uartService("6E400001-B5A3-F393-E0A9-E50E24DCCA9E"); // Custom UART service
BLECharacteristic rxChar("6E400002-B5A3-F393-E0A9-E50E24DCCA9E",
BLEWrite | BLEWriteWithoutResponse, 512);
void setup() {
Serial.begin(115200);
while (!Serial);
// Start BLE
if (!BLE.begin()) {
Serial.println("BLE start failed!");
while (1);
}
Serial.println("BLE UART Receiver Started");
// Advertise the service
BLE.setLocalName("Nano33BLE_UART");
BLE.setAdvertisedService(uartService);
uartService.addCharacteristic(rxChar);
BLE.addService(uartService);
BLE.advertise();
Serial.println("Waiting for BLE connection...");
}
void loop() {
BLEDevice central = BLE.central();
if (central) {
Serial.print("Connected to Central device");
//Serial.println(central.address());
while (central.connected()) {
if (rxChar.written()) {
const uint8_t* data = rxChar.value(); // raw bytes
int len = rxChar.valueLength(); // number of bytes received
if (len > 0) {
char buffer[513];
// copy bytes to char buffer
for (int i = 0; i < len; i++) {
buffer[i] = (char)data[i];
}
buffer[len] = '\0'; // null terminate
String incoming = buffer;
Serial.print("Received: ");
Serial.println(incoming);
}
}
}
Serial.println("Disconnected");
}
}
Explanation of this project in the below video
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