How to have user input (Nucleo-F401RE)

I am trying to make a system that takes a numeric user input in the console and then spins a motor that many times
(I want to have 2 inputs and 2 motors but I want to start smaller and build up, I also in the future want it to be able to read the inputs from a text file)
I have been looking at a lot of documentation that is out there relating to BufferedSerial but nothing I have tried seems to work.
Does anyone have any suggestions???


BufferedSerial sometimes can only read a part of the whole string (It is not affected by size of the buffer but probably by a processor speed/load), so you must collect all the parts and then process them.

For code example click here
#include "mbed.h"
#include <string>
#define FORMAT "1-100"

DigitalOut          led(LED1);

static BufferedSerial serial_port(USBTX, USBRX);

int main(){

    printf("Example start\nPlease enter motor ID and number of steps of that motor.\n");
    printf("ID-Steps \nFormat: %s\n", FORMAT);
    char buf[MAXIMUM_BUFFER_SIZE];
    string myString;
    int counter = 0;

    while (1) {
        if (uint32_t num =, sizeof(buf))) {
            // convert to string
            for (int i = 0; i < num; i++) { 
                // only string without  new line and carriage return
                if('\r' != buf[i] && '\n' != buf[i]){
                    myString += buf[i];
            // is complete
            if (counter >= sizeof(FORMAT)-1){
                int motorID = stoi(&myString[0]);
                int motorSteps = stoi(&myString[2]);
                // your motor magic here
                printf("Motor %d will run for %d steps\n", motorID, motorSteps);
                myString = "";
                counter = 0;
            led = !led;

It has been tested with this setup:

  • MbedOS 6.7,
  • MbedStudio 1.3.1
  • Boards - Nucleo-F429ZI, F446RE, F303RE
  • Serial terminals - Termite, Hercules, Putty and also Serial Monitor of the MbedStudio.

BR, Jan

Hello, Thank you for the help so far, I ran the code to ensure it would work and the output is looking like this
do you know what this might be, is it related to the buffer size?

Hmm, I don’t know.
Just try to commented out the first printf, that string is not necessary it is only for info how to use the rest.

BR, Jan