16 bit Timer counter count direction

Projects Programming
1

I am using counter 4 but it only seems to count down. I have the Wave generation mode set to 0 with WGM4 0 to 3 set to zero. I have read the atmel documentation multiple times but there only seems brief mention of "direction" for the control unit.

How do you set the count direction please.

3

It is the Mega 2560

5

Please post the code that demonstrates this. Use code tags.

6

The Arduino core may have initialized timers for "Phase Correct" PWM. If you're going to use a timer for purposes other than analogWrite(), make sure you initialize ALL of the control bits.

7

Here is the code, I suspect I am doing something daft, it's definitely counting down, it's not the end of the world just really annoying not knowing whats wrong. Ignore the ICR as I was going on the use that further in the project.

void setup()
{
Serial.begin(9600);
noInterrupts();
TCCR4A=0;
TCCR4B=0;
TCNT4=0;

TCCR4A |= (0 << WGM40);
TCCR4A |= (0 << WGM41);

TCCR4B |= (1 << ICNC4); // enable noice canceler
TCCR4B |= (1 << CS42);//128 prescaler
TCCR4B |= (0 << WGM42);
TCCR4B |= (0 << WGM43);

interrupts();
}

void loop()
{
Serial.print("counter =");Serial.println(TCNT4);
Serial.print("ICR =");Serial.println(ICR4);
Serial.print("TCCR4A =");Serial.println(TCCR4A);
Serial.print("TCCR4B =");Serial.println(TCCR4B);
Serial.println("");

delay(1000);
}
8

ORing with zero accomplishes nothing. What was your intent here?

TCCR4A |= (0 << WGM40);
TCCR4A |= (0 << WGM41);

The problem is that you are reading the counter every second, but it overflows within that time, so you see steadily decreasing counts.

Change the serial Baud rate to a modern rate, like 115200, and remove the delay to see the expected behavior.

1 Like
10

This is a classic case illustrating the Sampling Theorem, and the expected aliasing that results from sampling at a frequency less than the highest frequency in the input stream.

Like wagon wheels that appear to be rotating backwards in a cowboy Western movie.

1 Like
11

Well done guys, obvious when you point that out. Lesson learnt, thanks.

12

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