Serial monitor is blank when motor controlling and sensor reading with two nano 33 ble sense

fellasfellas · February 11, 2025, 10:27am

hello guys. i have two arduino nano 33 ble sense, one is peripheral and one is central and i used them for sensor communication via bluetooth and it was working until i added the motor task. my motor driver is L298N and i have four motors. i want central to give peripheral a command about how to run the motors. and my peripheral is connected to L298N by cables. but now i don't know if this part of my code is working or not because my central serial monitor is just blank and i don't even know if two nano 33 are connected via bluetooth. what can i do, can you please help me, thank you...

central code:

/*
  -----------------------------------------------------------------------------------------------
 | BLE_IMU_CENTRAL - Wireless IMU Communication with peripheral device
 |
 | Arduino Boards Tested: Nano 33 BLE Sense as a peripheral & Nano 33 BLE as central.
 | Code not tested for multiple peripherals
 |
 | This sketch works alongside the BLE_IMU_PERIPHERAL sketch to communicate with another Arduino BLE. 
 | This sketch can also be used with a generic BLE central app, like LightBlue (iOS and Android) or
 | nRF Connect (Android), to interact with the services and characteristics created in this sketch.
 |
 | This example code is adapted from the ArduinoBLE library, available in the public domain.
 | Authors: Aaron Yurkewich & Pilar Zhang Qiu
 | Latest Update: 25/02/2021
  -----------------------------------------------------------------------------------------------
*/

#include <ArduinoBLE.h>

//PASTEBEGIN
#include <Arduino_LSM9DS1.h>
//PASTEFINISH

// ------------------------------------------ BLE UUIDs ------------------------------------------
#define BLE_UUID_PERIPHERAL               "19B10000-E8F2-537E-4F6C-D104768A1214"  //please change to a unique value that matches BLE_IMU_PERIPHERAL
#define BLE_UUID_CHARACT_LED              "19B10001-E8F2-537E-4F6C-E104768A1214"  //please change to a unique value that matches BLE_IMU_PERIPHERAL
#define BLE_UUID_CHARACT_GYROX             "29B10001-E8F2-537E-4F6C-a204768A1215"  //please change to a unique value that matches BLE_IMU_PERIPHERAL
#define BLE_UUID_CHARACT_GYROY             "39B10001-E8F2-537E-4F6C-a204768A1215"  //please change to a unique value that matches BLE_IMU_PERIPHERAL
#define BLE_UUID_CHARACT_GYROZ             "49B10001-E8F2-537E-4F6C-a204768A1215"  //please change to a unique value that matches BLE_IMU_PERIPHERAL

//PASTEBEGIN
#define BLE_UUID_CHARACT_ACCA             "59B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_ACCB             "69B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_ACCC             "79B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL

#define BLE_UUID_CHARACT_MAGK             "89B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_MAGL             "99B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_MAGM             "09B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
//PASTEFINISH

//begin
BLEService motorService("19B10000-E8F2-537E-4F6C-E104768A1214");
BLEByteCharacteristic motorControlChar("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);
//end

// ------------------------------------------ VOID SETUP ------------------------------------------
void setup() {
  Serial.begin(9600);
  while (!Serial);

  // configure the button pin as input
  pinMode(LED_BUILTIN, OUTPUT);

  // initialize the BLE hardware
  BLE.begin();

  Serial.println("BLE Central - Gyroscope control");

  // start scanning for peripherals
  BLE.scanForUuid(BLE_UUID_PERIPHERAL);//
}

// ------------------------------------------ VOID LOOP ------------------------------------------
void loop() {
  // check if a peripheral has been discovered
  BLEDevice peripheral = BLE.available();

  if (peripheral) {
    // discovered a peripheral, print out address, local name, and advertised service
    Serial.print("Found ");
    Serial.print(peripheral.address());
    Serial.print(" '");
    Serial.print(peripheral.localName());
    Serial.print("' ");
    Serial.print("' ");
    Serial.print(peripheral.advertisedServiceUuid());
    Serial.println();

    if (peripheral.localName() != "BLE_IMU") {
      return;
    }

    // stop scanning
    BLE.stopScan();

    LED_IMU(peripheral);
    // peripheral disconnected, start scanning again
    BLE.scanForUuid(BLE_UUID_PERIPHERAL);

  }

}

// ------------------------------------------ FUNCTIONS ------------------------------------------
void LED_IMU(BLEDevice peripheral) {
  // connect to the peripheral
  Serial.println("Connecting ...");

  if (peripheral.connect()) {
    Serial.println("Connected");
  } else {
    Serial.println("Failed to connect!");
    return;
  }

  // discover peripheral attributes
  Serial.println("Discovering attributes ...");
  if (peripheral.discoverAttributes()) {
    Serial.println("Attributes discovered");
  } else {
    Serial.println("Attribute discovery failed!");
    peripheral.disconnect();
    return;
  }

  // retrieve the LED characteristic
  BLECharacteristic ledCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_LED);
  BLECharacteristic gyroXCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_GYROX);
  BLECharacteristic gyroYCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_GYROY);
  BLECharacteristic gyroZCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_GYROZ);

  //PASTEBEGIN
  BLECharacteristic accACharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_ACCA);
  BLECharacteristic accBCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_ACCB);
  BLECharacteristic accCCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_ACCC);
  
  BLECharacteristic magKCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_MAGK);
  BLECharacteristic magLCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_MAGL);
  BLECharacteristic magMCharacteristic = peripheral.characteristic(BLE_UUID_CHARACT_MAGM);
  //PASTEFINISH


  // check if an specific BLE characteristic exists
  if (!ledCharacteristic) {
    Serial.println("Peripheral does not have LED characteristic!");
    peripheral.disconnect();
    return;
  } else if (!ledCharacteristic.canWrite()) {
    Serial.println("Peripheral does not have a writable LED characteristic!");
    peripheral.disconnect();
    return;
  }

  
  int buttonState = 0;
  float x, y, z, a, b, c, k, l, m;
   
  while (peripheral.connected()) {

    //begin
      unsigned long start = millis();

        while (millis() - start < 2000){
          motorControlChar.writeValue(1);
          delay(100);
        }

        start = millis();

        while (millis() - start < 100){
          motorControlChar.writeValue(3);
          delay(100);
        }

        start = millis(); 

        while (millis() - start < 2000){
          motorControlChar.writeValue(1);
          delay(100);
        }

        start = millis();

        while (millis() - start < 100){
          motorControlChar.writeValue(4);
          delay(100);
        }

        start = millis(); 

        while (millis() - start < 2000){
          motorControlChar.writeValue(1);
          delay(100);
        }

        start = millis();

        while (millis() - start < 100){
          motorControlChar.writeValue(3);
          delay(100);
        }
 
        start = millis(); 

        while (millis() - start < 2000){
          motorControlChar.writeValue(2);
          delay(100);
        }

        start = millis();

        while (millis() - start < 100){
          motorControlChar.writeValue(3);
          delay(100);
        }
 
        start = millis(); 

        while (millis() - start < 2000){
          motorControlChar.writeValue(2);
          delay(100);
        }

        start = millis(); 

        while (millis() - start < 2000){
          motorControlChar.writeValue(4);
          delay(100);
        }
    //end

    // while the peripheral is connected
    // read the gyroscope values
    gyroXCharacteristic.readValue( &x, 4 );
    gyroYCharacteristic.readValue( &y, 4 );
    gyroZCharacteristic.readValue( &z, 4 );

    //PASTEBEGIN
    accACharacteristic.readValue( &a, 4 );
    accBCharacteristic.readValue( &b, 4 );
    accCCharacteristic.readValue( &c, 4 );

    magKCharacteristic.readValue( &k, 4 );
    magLCharacteristic.readValue( &l, 4 );
    magMCharacteristic.readValue( &m, 4 );
    //PASTEFINISH

    Serial.print(millis());
    Serial.print('\t');
    Serial.print(x);
    Serial.print('\t');
    Serial.print(y);
    Serial.print('\t');       
    Serial.print(z);
    Serial.print('\t');
    //PASTEBEGIN
    Serial.print(a);
    Serial.print('\t');
    Serial.print(b);
    Serial.print('\t');       
    Serial.print(c);
    Serial.print('\t');

    Serial.print(k);
    Serial.print('\t');
    Serial.print(l);
    Serial.print('\t');       
    Serial.println(m);
    //PASTEFINISH

    // make the LED blink
    if (buttonState == 0)
    {buttonState = 1;}
    else if (buttonState == 1)
    {buttonState = 0;}
    
    digitalWrite(LED_BUILTIN, buttonState);
      if (buttonState == 0) {
        // write 0x01 to turn the LED on
        ledCharacteristic.writeValue((byte)0x01);
      } else {
        // write 0x00 to turn the LED off
        ledCharacteristic.writeValue((byte)0x00);
      }
  }
  Serial.println("Peripheral disconnected");
}

peripheral code:

/*
  -----------------------------------------------------------------------------------------------
 | BLE_IMU_PERIPHERAL - Wireless IMU Communication with central device
 |
 | Arduino Boards Tested: Nano 33 BLE Sense as a peripheral & Nano 33 BLE as central.
 | Code not tested for multiple peripherals

 | This sketch works alongside the BLE_IMU_CENTRAL sketch to communicate with an Arduino Nano 33 BLE. 
 | This sketch can also be used with a generic BLE central app, like LightBlue (iOS and Android) or
 | nRF Connect (Android), to interact with the services and characteristics created in this sketch.
 
 | This example code is adapted from the ArduinoBLE library, available in the public domain.
 | Authors: Aaron Yurkewich & Pilar Zhang Qiu
 | Latest Update: 25/02/2021
  -----------------------------------------------------------------------------------------------
*/

#include <ArduinoBLE.h>
#include <Arduino_LSM9DS1.h>
//#include <Arduino_LSM6DS3.h> // Uncomment this if your peripheral is the Nano 33 IoT

// ------------------------------------------ BLE UUIDs ------------------------------------------
#define BLE_UUID_PERIPHERAL               "19B10000-E8F2-537E-4F6C-D104768A1214" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_LED              "19B10001-E8F2-537E-4F6C-E104768A1214" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_GYROX             "29B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_GYROY             "39B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_GYROZ             "49B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL

//PASTEBEGIN
#define BLE_UUID_CHARACT_ACCA             "59B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_ACCB             "69B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_ACCC             "79B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL

#define BLE_UUID_CHARACT_MAGK             "89B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_MAGL             "99B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
#define BLE_UUID_CHARACT_MAGM             "09B10001-E8F2-537E-4F6C-a204768A1215" //please chnage to a unique value that matches BLE_IMU_CENTRAL
//PASTEFINISH


BLEService LED_IMU_Service(BLE_UUID_PERIPHERAL); // BLE LED Service

//begin
BLEService motorService("19B10000-E8F2-537E-4F6C-E104768A1214");
BLEByteCharacteristic motorControlChar("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);
//end

// BLE LED Switch Characteristic - custom 128-bit UUID, read and writable by central
BLEByteCharacteristic switchCharacteristic(BLE_UUID_CHARACT_LED, BLERead | BLEWrite);
BLEFloatCharacteristic gyroXCharacteristic(BLE_UUID_CHARACT_GYROX, BLERead | BLENotify | BLEWrite);
BLEFloatCharacteristic gyroYCharacteristic(BLE_UUID_CHARACT_GYROY, BLERead | BLENotify | BLEWrite);
BLEFloatCharacteristic gyroZCharacteristic(BLE_UUID_CHARACT_GYROZ, BLERead | BLENotify | BLEWrite);


//PASTEBEGIN
BLEFloatCharacteristic accACharacteristic(BLE_UUID_CHARACT_ACCA, BLERead | BLENotify | BLEWrite);
BLEFloatCharacteristic accBCharacteristic(BLE_UUID_CHARACT_ACCB, BLERead | BLENotify | BLEWrite);
BLEFloatCharacteristic accCCharacteristic(BLE_UUID_CHARACT_ACCC, BLERead | BLENotify | BLEWrite);

BLEFloatCharacteristic magKCharacteristic(BLE_UUID_CHARACT_MAGK, BLERead | BLENotify | BLEWrite);
BLEFloatCharacteristic magLCharacteristic(BLE_UUID_CHARACT_MAGL, BLERead | BLENotify | BLEWrite);
BLEFloatCharacteristic magMCharacteristic(BLE_UUID_CHARACT_MAGM, BLERead | BLENotify | BLEWrite);
//PASTEFINISH

//begin
int enA=3;
int enB=5;
int in1=2;
int in2=4;
int in3=6;
int in4=7;
//end

const int ledPin = LED_BUILTIN; // pin to use for the LED
float x, y, z, a, b, c, k, l, m;



// ------------------------------------------ VOID SETUP ------------------------------------------
void setup() {

  //PASTEBEGIN
  pinMode(enA, OUTPUT);
  pinMode(enB, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT);
  //PASTEFINISH

  Serial.begin(9600); 
  //while (!Serial); //uncomment to view the IMU data in the peripheral serial monitor

  // begin IMU initialization
  if (!IMU.begin()) {
    Serial.println("Failed to initialize IMU!");
    while (1);
  }

  // set LED pin to output mode
  pinMode(ledPin, OUTPUT);

  // begin BLE initialization
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");
    while (1);
  }

  // set advertised local name and service UUID:
  BLE.setLocalName("BLE_IMU");
  BLE.setAdvertisedService(LED_IMU_Service);

  //begin
  BLE.setLocalName("MotorControlPeripheral");
  BLE.setAdvertisedService(motorService);
  motorService.addCharacteristic(motorControlChar);
  //end

  // add the characteristic to the service
  LED_IMU_Service.addCharacteristic(switchCharacteristic);
  LED_IMU_Service.addCharacteristic(gyroXCharacteristic);
  LED_IMU_Service.addCharacteristic(gyroYCharacteristic);
  LED_IMU_Service.addCharacteristic(gyroZCharacteristic);

  //PASTEBEGIN
  LED_IMU_Service.addCharacteristic(accACharacteristic);
  LED_IMU_Service.addCharacteristic(accBCharacteristic);
  LED_IMU_Service.addCharacteristic(accCCharacteristic);

  LED_IMU_Service.addCharacteristic(magKCharacteristic);
  LED_IMU_Service.addCharacteristic(magLCharacteristic);
  LED_IMU_Service.addCharacteristic(magMCharacteristic);
  //PASTEFINISH

  // add service
  BLE.addService(LED_IMU_Service);

  //begin
  BLE.addService(motorService);
  //end

  // set the initial value for the characeristic:
  switchCharacteristic.writeValue(0);

  //begin
  motorControlChar.writeValue(0);
  //end

  // start advertising
  BLE.advertise();

  Serial.println("BLE LED Peripheral");

  //PASTEBEGIN
  /*Serial.begin(9600);
  while (!Serial);
  Serial.println("Started");

  if (!IMU.begin()) {
    Serial.println("Failed to initialize IMU!");
    while (1);
  }

  Serial.print("Accelerometer sample rate = ");
  Serial.print(IMU.accelerationSampleRate());
  Serial.println(" Hz");
  Serial.println();
  Serial.println("Acceleration in g's");
  Serial.println("A\tB\tC");
  
  if (!IMU.begin()) {
    Serial.println("Failed to initialize IMU!");
    while (1);
  }
  Serial.print("Magnetic field sample rate = ");
  Serial.print(IMU.magneticFieldSampleRate());
  Serial.println(" Hz");
  Serial.println();
  Serial.println("Magnetic Field in uT");
  Serial.println("K\tL\tM");
  */
  //PASTEFINISH
}

// ------------------------------------------ VOID LOOP ------------------------------------------
void loop() {
  
  // listen for BLE peripherals to connect:
  BLEDevice central = BLE.central();

  // if a central is connected to peripheral:
  if (central) {
    Serial.print("Connected to central: ");
    // print the central's MAC address:
    Serial.println(central.address());

    // while the central is still connected to peripheral:
    while (central.connected()) {
      // if the remote device wrote to the characteristic,
      // use the value to control the LED:

      if (switchCharacteristic.written()) {
        if (switchCharacteristic.value()) {   // any value other than 0
          Serial.println("LED on");
          digitalWrite(ledPin, HIGH);         // will turn the LED on
        } else {                              // a 0 value
          Serial.println(F("LED off"));
          digitalWrite(ledPin, LOW);          // will turn the LED off
        }
      }

      if (IMU.gyroscopeAvailable()) {
        IMU.readGyroscope(x, y, z);

        gyroXCharacteristic.writeValue(x);
        gyroYCharacteristic.writeValue(y);
        gyroZCharacteristic.writeValue(z);
        

        Serial.print(millis());
        Serial.print('\t');
        Serial.print(x); 
        Serial.print('\t');
        Serial.print(y); 
        Serial.print('\t');         
        Serial.print(z); 
        Serial.print('\t'); 
      }


      //PASTEBEGIN
      if (IMU.accelerationAvailable()) {
        IMU.readAcceleration(a, b, c);

        accACharacteristic.writeValue(a);
        accBCharacteristic.writeValue(b);
        accCCharacteristic.writeValue(c);
        

        Serial.print(a);
        Serial.print('\t');
        Serial.print(b);
        Serial.print('\t');
        Serial.print(c);
        Serial.print('\t');
      }

      if (IMU.magneticFieldAvailable()) {
        IMU.readMagneticField(k, l, m);

        magKCharacteristic.writeValue(k);
        magLCharacteristic.writeValue(l);
        magMCharacteristic.writeValue(m);

        Serial.print(k);
        Serial.print('\t');
        Serial.print(l);
        Serial.print('\t');
        Serial.println(m);
      }
      //PASTEFINISH

      //begin
      if (motorControlChar.written()) {
        byte motorCommand = motorControlChar.value();

        // Motor kontrolü
        if (motorCommand == 1) {
          // İleri düz hareket
          analogWrite(enA, 120);
          digitalWrite(in1, HIGH);
          digitalWrite(in2, LOW);

          analogWrite(enB, 120);
          digitalWrite(in3, HIGH);
          digitalWrite(in4, LOW);
        } else if (motorCommand == 2) {
          // Geri düz hareket
          analogWrite(enA, 120);
          digitalWrite(in1, LOW);
          digitalWrite(in2, HIGH);

          analogWrite(enB, 120);
          digitalWrite(in3, LOW);
          digitalWrite(in4, HIGH);
        } else if (motorCommand == 3) {
          // İleri sağa hareket
          analogWrite(enA, 120);
          digitalWrite(in1, HIGH);
          digitalWrite(in2, LOW);

          analogWrite(enB, 120);
          digitalWrite(in3, LOW);
          digitalWrite(in4, HIGH);
        } else if (motorCommand == 4) {
          // İleri sola hareket
          analogWrite(enA, 120);
          digitalWrite(in1, LOW);
          digitalWrite(in2, HIGH);

          analogWrite(enB, 120);
          digitalWrite(in3, HIGH);
          digitalWrite(in4, LOW);
        } else if (motorCommand == 0) {
          // Dur
          analogWrite(enA, 0);
          analogWrite(enB, 0);
        }
      }
      //end

    }

      // when the central disconnects, print it out:
      Serial.print(F("Disconnected from central: "));
      Serial.println(central.address());
    }

  }

peripheral device which is connected to L298N by cables:

L298N:

motors:

gcjr · February 11, 2025, 10:45am

can you describe how your 2 programs work and interact?

i see a connection to central, but i don't see where anything is read from it

fellasfellas · February 11, 2025, 10:56am

they connect with bluetooth and they recognize eachother by the same characteristic uuid.

gcjr · February 11, 2025, 11:07am

???

fellasfellas · February 11, 2025, 11:18am

it reads all the sensor data with readValue and writeValue but i dont know about the motor task. but the problem is different from all these. my serial monitor is total blank or it keeps warning the same thing:

gcjr · February 11, 2025, 11:35am

don't see the point of having BT communication if nothing is being read and wouldn't expect anything to happen if commands are being read and processed.

can you explain the flow of your code? maybe i'm missing something

system · August 10, 2025, 11:36am

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Serial monitor is blank when motor controlling and sensor reading with two nano 33 ble sense

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