EEESAU Wiki

1.2 Serial Monitor

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Using serial over USB to print messages from the Pico.

C Interface

Documentation

#include "pico/stdlib.h"
 
// Initialise the Standard I/O interface.
stdio_init_all();
 
// Print a formatted string
stdio_printf(const char* format, ...);

Instructions

You can use a USB serial monitor program to trace output logs from the Pico. This is useful to print out some basic debugging information or to get some external input.

In the C code, you need to add the following function call to your main() function, to turn on the serial communication:

stdio_init_all();

VSCode has a built-in serial monitor, you can find it as one of the tabs in the “Terminal”:

Other serial monitor programs are:

  • PuTTY (Windows)
  • minicom (Linux, macOS)

Build and upload the serial-monitor program, connect the serial port and then reset the Pico. You should see a message appear in the log.

  • On Linux/macOS, the serial port is /dev/ttyACM0
  • On Windows, the serial port will be called COM* where * is a number.

Serial Input

The serial monitor can also be used to send inputs to the Pico over USB. Open the serial-monitor-input.cpp file to see how to do this.

A helper function has been written to make the process easier.

size_t gets_s(char* string, size_t string_size);

The code in serial-monitor-input.cpp asks the user for a password, then prints a message depending on whether it is correct or not.

Exercise

Can you make a short quiz using the serial input and output?

Print a message to ask a question, and then when the user gives an answer, print out “Correct” or “Incorrect”.

Hint: use the strcmp function to check if strings are equal.

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