HZ in Pulse delay..?

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1

I`m testing pulse for HZ.

ex) I`d like to make a pulse 700HZ, hz/s ->> 1/700,
700hz ->1428571.428~ns -> 22,857clock (Uno 62.5ns / cal)

pulse up +down are one cycle(50%duty). UP & Down each 11428.5clock

Theoretically, it is considered to be 1 cycle every 4 times.(at 2857)
2 times to read the "for" statement, 2 times "for" the sub phrase.
but 700HZ was output only when a value corresponding to approx5.06(not4) was put (at 2258) in osciliscope.

Why does the code properly differ so much from the theory?

Thank you./

#define FG3 3

void setup()
{
pinMode(3, FG3);
}

void loop()
{
digitalWrite(FG3, HIGH);

for(int test=0; test<2857;test++){
asm volatile("nop");
}
digitalWrite(FG3, LOW);
for(int test=0; test<2857;test++){
asm volatile("nop");
}
}

2

Loop overheads?

Please remember to use code tags when posting code.

(What is pinMode 3? Why not use a predefine?)

3

Hello young_k
Do I understand you right that you like to get a PWM (Puls Width Modulation) Signal with 700Hz and 50% Duyt Cycle? If so why not do this via the Interrupt timer? I made a code to get a 10ms and 100ms task raster for doing some calcalation. The adapted frame looks like this:

bool pintoggle = LOW;        // toggle out pin

void setup()
{
    noInterrupts();           // suspent interrupts
    TCCR1A = 0;               // Reset entire TCCR1A register
    TCCR1B = 0;               // Reset entire TCCR1B register
    TCCR1B |= B00000001;      // Set CS10 to 1 so we get Prescalar = 1
    TIMSK1 |= B00000010;      // Set OCIE1A to 1 will enable compare match A
    OCR1A = 11428;            // OCR1A = 11428 will give 700Hz Calculation: 1,428571428571ms / (62,5ns) /2 = 11428
    TCNT1 = 0;                // Set Counter1 value to 0
    interrupts();
    

    pinMode(2, OUTPUT);        // Used for measurement with Oscilloscop
 
}

 
void loop()
{

 
}


ISR(TIMER1_COMPA_vect)
{
    TCNT1  = 0;                     // First, set the timer back to 0 so it resets for next interrupt


   if (pintoggle == LOW) {
      pintoggle = HIGH;
    } else {
      pintoggle = LOW;
    }

    // set the LED with the ledState of the variable:
    digitalWrite(2, pintoggle);
}

The TCCR1B OCR1A register settings have been adapted to your 700Hz.
Please let me know if I am on the right way for your problem? Observe digital Output 2 with Oszi.

Please check the video with good background on Interrupt usage:

4

Hi.
Im sorry because im start user.

pin3 from UNO is using for PWM channel.

5

I will check this code.
I hope It will help me to study
Thank you for your help.

6

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