Hello, I am new to microcontrollers programming. I just got my hands on the arduino uno board. I am trying to build the popular "bluetooth robot car" using the uno, adafruit motorshield v1 and HC-05 bluetooth module. My code /******************* Robot Remote Control Mode ********************/ // include the Adafruit motor v1 library #include AF_DCMotor MotorFR(1); // Motor for drive Front Right on M1 AF_DCMotor MotorFL(2); // Motor for drive Front Left on M2 AF_DCMotor MotorBL(3); // Motor for drive Back Left on M3 AF_DCMotor MotorBR(4); // Motor for drive Back Right on M4 const int buzPin = 2; // set digital pin 2 as buzzer pin (use active buzzer) const int ledPin = A5; // set digital pin A5 as LED pin (use super bright LED) int valSpeed=255; void setup(){ Serial.begin(9600); // set up Serial library at 9600 bps Serial.println("*Robot Remote Control Mode*"); pinMode(buzPin, OUTPUT); // sets the buzzer pin as an Output pinMode(ledPin, OUTPUT); // sets the LED pin as an Output // Set the speed to start, from 0 (off) to 255 (max speed) MotorFL.setSpeed(valSpeed); MotorFR.setSpeed(valSpeed); MotorBL.setSpeed(valSpeed); MotorBR.setSpeed(valSpeed); // turn off motor MotorFL.run(RELEASE); MotorFR.run(RELEASE); MotorBL.run(RELEASE); MotorBR.run(RELEASE); } void loop() { while (Serial.available() > 0) { char command = Serial.read(); // gets one byte from serial buffer Serial.println(command); switch(command){ case 'F': // move forward SetSpeed(valSpeed); MotorFL.run(FORWARD); MotorFR.run(FORWARD); MotorBL.run(FORWARD); MotorBR.run(FORWARD); break; case 'B': // move backward SetSpeed(valSpeed); MotorFL.run(BACKWARD); MotorFR.run(BACKWARD); MotorBL.run(BACKWARD); MotorBR.run(BACKWARD); break; case 'R': // turn right SetSpeed(valSpeed); MotorFL.run(FORWARD); MotorFR.run(BACKWARD); MotorBL.run(FORWARD); MotorBR.run(BACKWARD); break; case 'L': // turn left SetSpeed(valSpeed); MotorFL.run(BACKWARD); MotorFR.run(FORWARD); MotorBL.run(BACKWARD); MotorBR.run(FORWARD); break; case 'G': // forward left MotorFL.setSpeed(valSpeed/4); MotorBL.setSpeed(valSpeed/4); MotorFL.run(FORWARD); MotorFR.run(FORWARD); MotorBL.run(FORWARD); MotorBR.run(FORWARD); break; case 'H': // backward left MotorFL.setSpeed(valSpeed/4); MotorBL.setSpeed(valSpeed/4); MotorFL.run(BACKWARD); MotorFR.run(BACKWARD); MotorBL.run(BACKWARD); MotorBR.run(BACKWARD); break; case 'I': // forward right MotorFR.setSpeed(valSpeed/4); MotorBR.setSpeed(valSpeed/4); MotorFL.run(FORWARD); MotorFR.run(FORWARD); MotorBL.run(FORWARD); MotorBR.run(FORWARD); break; case 'J': // backward right MotorFR.setSpeed(valSpeed/4); MotorBR.setSpeed(valSpeed/4); MotorFL.run(BACKWARD); MotorFR.run(BACKWARD); MotorBL.run(BACKWARD); MotorBR.run(BACKWARD); break; case 'S': // stop MotorFL.run(RELEASE); MotorFR.run(RELEASE); MotorBL.run(RELEASE); MotorBR.run(RELEASE); break; case 'V': // beep buzzer digitalWrite(buzPin, HIGH); delay(150); digitalWrite(buzPin, LOW); delay(100); digitalWrite(buzPin, HIGH); delay(250); digitalWrite(buzPin, LOW); break; case 'W': // turn light on digitalWrite(ledPin, HIGH); break; case 'w': // turn light off digitalWrite(ledPin, LOW); break; case '0': // set speed motor to 0 (min) SetSpeed(0); break; case '1': // set speed motor to 30 SetSpeed(30); break; case '2': // set speed motor to 55 SetSpeed(55); break; case '3': // set speed motor to 80 SetSpeed(80); break; case '4': // set speed motor to 105 SetSpeed(105); break; case '5': // set speed motor to 130 SetSpeed(130); break; case '6': // set speed motor to 155 SetSpeed(155); break; case '7': // set speed motor to 180 SetSpeed(180); break; case '8': // set speed motor to 205 SetSpeed(205); break; case '9': // set speed motor to 230 SetSpeed(230); break; case 'q': // set speed motor to 255 (max) SetSpeed(255); break; } } } // function for setting speed of motors void SetSpeed(int val){ valSpeed = val; MotorFL.setSpeed(val); MotorFR.setSpeed(val); MotorBL.setSpeed(val); MotorBR.setSpeed(val); } Compiles and uploads without any error or warning. While not stacking the shield and not attaching the bluetooth module, instead seeing "Robot remote control mode" on the serial monitor, I see some "Rbnld tedisjvv shhsjj hshhs". When I attach and connect the bluetooth module and send a command 'R', instead of seeing 'R' on the monitor I see 'R' followed by an up-pointing arrow. I tried to search for help in stack-overflow for similar problem but none has helped. I have tried other codes for serial communication(like blinking an led when 'B' is read from serial) and it worked perfectly.I need help.

Your uploaded code has the port speed set at 9600 baud. You must set the speed for the Serial monitor the same. Or change the code to match the Serial Monitor (it may be 155200 baud by default).

My Serial monitor is at 9600 baudrate and it works fine if I run a sketch without including any library.

[image] braingix: Compiles and uploads without any error or warning. In which case it's not a topic for Installation and Troubleshooting (see About the IDE 1.x category) and hence your topic has been moved.

Kindly share the circuit diagram

I have this issue when I have nothing connected to the arduino, just the board hooked up to my computer. If I compile const int led=7; void setup(){ Serial.begin(9600); pinMode(led, OUTPUT); //led attached on pin 7 Serial.println("Led pin configured"); } void loop(){ while(Serial.available()>0){ char command=Serial.read(); //read a byte from serial Serial.println(command); switch(command){ case 'F': digitalWrite(led, HIGH); Serial.println("led turned on"); break; case 'B': digitalWrite(led, LOW); Serial.println("led turned off"); break; } } } everything works fine. The problem starts when I include the "AFMotor.h" and create an AF_DCMotor object. I don't know what is wrong with using the library. I have tried uninstalling and reinstalling the library. Even trying the examples in the library gives the same issue.

Sorry, I am new to the platform. I couldn't find any tag that describes my issue than this one.

[image] braingix: I have this issue when I have nothing connected to the arduino, just the board hooked up to my computer. Have you tried another Arduino? Maybe your hardware connections burned a pin. Have you tested the Arduino with simple serial sketches to verify the serial operation separately from the motor sketch? Use divide and conquer methodology.

Issue with Using libraries

Projects General Guidance

anon57585045 August 21, 2022, 1:13am 4

Please post a wiring diagram.

Topic		Replies	Views
Arduino UNO - fatal error: Tone.h: No such file or directory - Neuling ohne Plan Deutsch	25	418	June 6, 2026
Arduino robot problem General Guidance	46	1710	January 5, 2024
Inconcistency with motors and an ESP32, H Bridge Programming	7	226	October 24, 2026
AFmotor.h not compiling Programming	22	527	November 17, 2025
Add <IRremote> to library General Guidance	23	869	May 28, 2026

Issue with Using libraries

Related topics