Arduino Basics: Debugging

Debugging is the process of identifying and fixing problems in your Arduino code or circuits. Effective debugging helps you find errors quickly and ensures your projects work reliably.

1. Using the Serial Monitor

The Serial Monitor is one of the most powerful tools for debugging Arduino sketches. It allows your Arduino to send information to your computer for inspection.

• Initialize the serial communication in setup():

void setup() {
  Serial.begin(9600); // Start serial communication at 9600 baud
}

int sensorValue = analogRead(A0);
Serial.print("Sensor reading: ");
Serial.println(sensorValue);

2. Checking Connection Issues

• Verify the correct **board type** is selected in Tools → Board.
• Verify the correct **COM port** is selected in Tools → Port.
• Reset the board if necessary using the reset button.

3. Installing Drivers

Some Arduino clones use USB-to-serial chips like CH340 or CP2102. If your board is not detected:

• Download and install the correct driver for your operating system.
• After installation, reconnect the board and check the COM port again.

4. Using the Right USB Cables

• Not all USB cables support data transfer—some are power-only (charging cables).
• Use a data-capable cable to upload sketches and communicate via Serial Monitor.

5. Hardware Checks

• Check for loose jumper wires or components on the breadboard.
• Test basic functionality using the **built-in LED** (usually pin 13) with a simple blink sketch.
• Measure voltages with a multimeter if necessary.

6. Understanding Common Error Messages

• avrdude: stk500_recv(): programmer is not responding – Usually means wrong COM port, board type, or bad USB connection.
• ‘x’ was not declared in this scope – Variable or function is used before being defined.
• exit status 1 – Generic compilation error; check preceding error messages for specifics.
• board not found – Driver missing or USB cable issue.

7. Debugging Tips

• Break your code into smaller sections and test each part individually.
• Add Serial.println() statements at key points to track program flow and variable values.
• Check wiring and connections before modifying code—hardware issues are common causes of errors.
• Keep sketches organized with comments to make debugging easier.

Example: Debugging a Sensor

int sensorPin = A0;
int sensorValue = 0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  sensorValue = analogRead(sensorPin);      // Read sensor value
  Serial.print("Sensor: ");                 
  Serial.println(sensorValue);              // Print value