Loop doesn't execute

Projects Programming
1

I'm trying to debug a problem and hope someone here can help. In the following code the second loop in loop() doesn't execute:

/*
 Fading

 This example shows how to fade an LED using the analogWrite() function.

 The circuit:
 * LED attached from digital pin 9 to ground.

 Created 1 Nov 2008
 By David A. Mellis
 modified 30 Aug 2011
 By Tom Igoe

 http://www.arduino.cc/en/Tutorial/Fading

 This example code is in the public domain.

 */


int ledPin = 23;

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

void loop() 
{
   for (uint8_t fadeValue = 0 ; fadeValue <= 255; ++fadeValue) 
  {
    Serial.println(fadeValue);
    analogWrite(ledPin, fadeValue);
    delay(90);
  } 

  for (uint8_t fadeValue = 255 ; fadeValue >= 0; --fadeValue) 
  {
    Serial.println(fadeValue);
    analogWrite(ledPin, fadeValue);
    delay(90);
  }

}

I've tried this with both a Teensy and Arduino Nano. This effort was with the Teensy, which is why the pin number was chosen. For the Nano, I checked the pinout from http://marcusjenkins.com/wp-content/uploads/2014/06/nano.pdf to be sure I used a PWM capable pin.

Anyone see what I'm doing wrong?

Thanks

Joe

2

Anyone see what I'm doing wrong?

Look carefully at the size of the variable you're using as the loop control.

3

Look at what the compiler has to say (you may need to make it more verbose):

warning: comparison is always true due to limited range of data type [-Wtype-limits]
for (uint8_t fadeValue = 0 ; fadeValue <= 255; ++fadeValue)

4

wildbill:
Look at what the compiler has to say (you may need to make it more verbose):

warning: comparison is always true due to limited range of data type [-Wtype-limits]
for (uint8_t fadeValue = 0 ; fadeValue <= 255; ++fadeValue)

I don't understand. uint8_t is capable of representing 0 - 255. The loop stops at

AWOL:
Look carefully at the size of the variable you're using as the loop control.

Uugh, I knew I'd stared at it too long. Thanks

5

What you want is:

   uint8_t fadeValue = 0 ;
   do
   {
     <loop body>
   } while ++fadeValue != 0 ;

or

   uint8_t fadeValue = 0 ;
   do
   {
     <loop body>
   } while fadeValue++ < 255 ;