Simple Analog Output Sketch not working

Projects Programming
1

A simple sketch in Simon Monk book sets out the code below where you simply enter a number of between 0 and 255 eg to get corresponding reading on a multimeter (positive lead attached to digital pin 6 and negative to gnd etc,
Anyway, no matter what number i insert in serial monitor the voltage does not go beyond, say 0.7 volts DC. In other words, there is indeed a jump in DCv but it does not reflect the range 0-5v analog for 0-255 digital input.

Any ideas?

Thanks

void setup() {
pinMode(6, OUTPUT);
Serial.begin(9600);

}

void loop() {
if (Serial.available())
{
int dutyCycle = Serial.parseInt();
analogWrite(6, dutyCycle);
}

}

2

Book: https://www.udemy.com/course/programming-arduino/

When you send something via the Serial Monitor, there migth be a CarriageReturn or LineFeed or both after the text. The Serial.parseInt() does not read that, so the next time the loop() runs, the Serial.parseInt() sees those CarriageReturn and LineFeed, but it can not make a number of it, so it returns zero.

Solution: Get rid of those CarriageReturn and LineFeed.

void setup() 
{
  pinMode(6, OUTPUT);
  Serial.begin(9600);
  Serial.println("Type a number");
}

void loop() 
{
  if (Serial.available() > 0)
  {
    int dutyCycle = Serial.parseInt();
    analogWrite(6, dutyCycle);

    // Remove any CarriageReturn or LineFeed
    while (Serial.available() > 0)
    {
      Serial.read();
    }
  }
}
3

if that doesn’t do it for you, please post a schematic of your wiring - including where you test the output voltage with the DMM

thanks

4

Thanks Koepel, that worked. You’re a genius! Really appreciated!
Tim

Tim Flahvin | Partner
Thomson Geer
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5

could use Serial.readBytesUntil()

char buf [80];

void
loop (void)
{
    if (Serial.available ()) {
        int n = Serial.readBytesUntil ('\n', buf, sizeof(buf)-1);
        buf [n] = '\0';
        int val = atoi (buf);
        Serial.println (val);
    }
}

void
setup (void)
{
    Serial.begin (9600);
}
6

@gcjr You should know that you get into trouble if you use those Stream functions.

  • What if there is only a '\r' ?
  • What if a serial terminal program has a bug and has switched them and sends "\n\r" at the end ?
  • What if someone types numbers with a total length of 90 ?
  • What if someone types "100000" ?

@tflahvin The return value of Serial.parseInt() is 'long', see the reference: Serial.parseInt() - Arduino Reference
If someone types "100000" with the Serial.parseInt() and then convert it to a 'int', then you get a negative number.

This is a little better:

  long dutyCycle = Serial.parseInt();   // it returns a long
  if( dutyCycle < 0)
    dutyCycle = 0;
  if( dutyCycle > 255)
    dutyCycle = 255;
  analogWrite(6, (int) dutyCycle);
7

all things that can be easily dealt with for other types of inputs, but certainly not issues to simply read a number

the OP needs to invest the time to understand what the code does and its limitations

9

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