Serial Port not working well

[carloszb07]

I started with arduino last week and now Im trying a project where I have to use the serial port but this one when I try to read inputs from the computer doesnt read them well.
In this code if I dont write anything it prints the number -1 but if I write a number between 0-9 it prints 48-57 and then a 10 always. Someone can help me with that pls Im using an arduino UNO.

#include <LedControl.h>

LedControl lc = LedControl(11,10,9,0);
int r;

void setup() {
  // put your setup code here, to run once:
  lc.shutdown(0,true);
  Serial.begin(9600);

}

void loop() {
  // put your main code here, to run repeatedly:
r=Serial.read();
Serial.println(r);
delay(4000);

}

[groundFungus]

You need to check if there is data available before you read the from port.

The serial input basics tutorial will help you to reliably read serial data.

[anon57585045]

You posted in the wrong forum category.

[b707]

@carloszb07

n this code if I dont write anything it prints the number -1

"-1" is means that nothing to read in the port
Before reading from Serial port, first you need to check if there is something to read there

[GolamMostafa]

@groundFungus

You need to check if there is data available before you read the from port.

From buffer instead of port?

[b707]

@carloszb07

if I write a number between 0-9 it prints 48-57

change type of r variable to char instead of int, because if you type something in the Monitor - it send chars to Serial

[groundFungus]

If you will.

[anon57585045]

@b707

change type of r variable to char instead of int

If you do that, you can not test for a character available by the usual method of checking for -1 because char is unsigned. You would have to use the available() method instead.

[wildbill]

@carloszb07, Your topic moved to programming questions.

You issue relates to confusion between ASCII character numbers and the characters themselves as alluded to in reply #6

[GolamMostafa]

@anon57585045

char is unsigned.

In Arduino -- since when?

[anon57585045]

Right. 'char' is signed. An int will cast in an assignment to a char correctly as long as it doesn't overflow the char.