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I am implementing BLE with a HM-10 connected to an arduino UNO.

I have encountered an issue where attempting to add another characteristic results in the overwrite of the first one, leaving me with only one characteristic. Is it possible to implement multiple characteristics, and if so, how can I achieve this in my Arduino code?

Any assistance would be greatly appreciated.

#include <SoftwareSerial.h>

SoftwareSerial HM10(2, 3); // RX, TX, or choose any other suitable pins

byte vspeedValue = 0xEE; // Value for "vspeed" characteristic in hexadecimal
byte rpmValue = 0xAA;    // Value for "rpm" characteristic in hexadecimal

void sendATCommand(String command) {
  HM10.println(command);
  delay(500); // Allow time for the HM-10 to respond
  while (HM10.available()) {
    Serial.println(HM10.readString());
  }
}

void setup() {
  Serial.begin(9600);
  HM10.begin(9600); // Initialize SoftwareSerial for HM-10

  // Configure HM-10
  sendATCommand("AT+ROLE0"); // Set the HM-10 as a peripheral (GATT server)
  sendATCommand("AT+UUID0xFFE0"); // Set a custom service UUID (0xFFE0)

  // Define and set the "vspeed" characteristic with UUID 0xFFE1
  sendATCommand("AT+CHAR0xFFE3");

  // Define and set the "rpm" characteristic with UUID 0xFFE2
  sendATCommand("AT+CHAR0xFFE4");

  sendATCommand("AT+NAMEYourDeviceName"); // Set the device name

  delay(500); // Give the HM-10 some time to configure

  Serial.println("Peripheral device is advertising...");
}

void loop() {
  // Use AT commands to write data to the "vspeed" characteristic
  String atCommandVSpeed = "AT+CHAR0xFFE1=" + String(vspeedValue);
  sendATCommand(atCommandVSpeed);

  // Use AT commands to write data to the "rpm" characteristic
  //String atCommandRPM = "AT+CHAR0xFFE2=" + String(rpmValue);
  //sendATCommand(atCommandRPM);

  // Wait for a moment (optional)
  delay(5000); // Delay for 5 seconds before sending the next values
}
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  • 2
    HM-10 supports only one custom service with one custom characteristic. AT+UUID does not add new service. It simple changes its UUID. Once module connected it switches to binary mode. So to send data you simple write to UART, to read data simple read from UART. Nov 13, 2023 at 19:32

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