Self-diagnose components in the circuit How can I tackle self-diagnosis problem within my Arduino project?
For example, I have a temperature sensor and humidity sensor. How can I know if they work or not on Arduino start or inside the sketch loop?
You could get your program to output messages to the serial pin on your board, Tx. For example:

Serial.begin(9600) //baud rate of 9600

Serial.print("Debug Message");


You can use this to print out string and integers. Here is the link to further information on the Arduino website - https://www.arduino.cc/en/reference/serial

If you are already using the Serial pins then you could use the SoftwareSerial Library - https://www.arduino.cc/en/Reference/softwareSerial

This library allows you to make two other pins on your board Tx and Rx. For example:

SoftwareSerial mySerial(12,13) //Makes pin 12 Rx and pin 13 Tx

mySerial.begin(9600) //baud rate of 9600

mySerial.println("Debug Message");


To read the output from any of the pins on your arduino - use a USB to TTL serial cable. Plug it into your computer and use a program like PuTTY to connect to the serial cable and read the messages coming from the Arduino.