Synchronization between two outputs

Projects General Guidance
1

I am working on a project that requires synchronization between two outputs.

So my program is like

digitalWrite(2,HIGH);
analogWrite(3,20);

something like that.

However, the two outputs have a different frequency so they cannot synchronize. The difference is about twenty-something Hz. Is there anything I can do to synchronize the two outputs or to minimize the difference? Thank you.

2

Post the whole code ...

3

jasone111:
digitalWrite(2,HIGH);

That'd be about 0 Hz.

analogWrite(3,20);

That'd be about 490 Hz.

Now if you'd use pin 3 and 11 and use analogWrite on both, they'd be perfectly in sync.

4

This is the simplified version of my program.

void setup() {
pinMode(5,OUTPUT);
pinMode(3,OUTPUT);
}

void loop() {
digitalWrite(3,LOW);
analogWrite(5,30);
digitalWrite(3,HIGH);
}

If the signal is connected to an oscilloscope, there will be 11us difference between the two outputs. How can I correct it?

5

Step back a bit and explain what you are actually trying to do, this sounds to be an xyproblem. xyproblem.info

6

MarkT:
explain what you are actually trying to do,

That's what I said in the OP's other thread here, which may or may not be related.

hannah_mackinlay:
I think the OP should say what they're trying to do.

7

If you want two outputs to change state at the exact same state, make sure they're on the same PORT and use a register call setting or clearing both bit in the same instruction.

Of course it's hard to do this when one of the signals is PWM.

As you apparently have a steady delay between the two, make me wonder: does analogWrite() reset the counter related to that output (TCNT2 in case of pin 3)? If not, the delay should vary.