Hi , I need to check the frequency of a digitalwave. It is important to do this precise. I must be able to differ periods like 28us 26us and more.
Since arduino provides 1us delay at it's shortest , it is very useless for this. I think I must be able to do this using Spi. Since spi can read up to 8mhz which gives 1us/8 , I can track when a digital signal goes 5 and goes 0 precisely.
Can I use arduino uno as a perfect slave which reads continously ?
How can I manipulate the sck pin ?

 

you want to check frequency of some signal?
why not count pulses in some time interval and calculate frequency from there?

 

you want to check frequency of some signal?
why not count pulses in some time interval and calculate frequency from there?

its changing real quick this is not a mission I can go though measurements and avarage it

 

Can I use smth like this If I write an algorithm without spi ?

void wait500ns() {
  // 8 NOP = 8 x 62.5 ns = 500 ns
  asm volatile (
    "nop\n\t"  // 1. NOP = 62.5 ns
    "nop\n\t"  // 2. NOP = 62.5 ns
    "nop\n\t"  // 3. NOP = 62.5 ns
    "nop\n\t"  // 4. NOP = 62.5 ns
    "nop\n\t"  // 5. NOP = 62.5 ns
    "nop\n\t"  // 6. NOP = 62.5 ns
    "nop\n\t"  // 7. NOP = 62.5 ns
    "nop\n\t"  // 8. NOP = 62.5 ns (Toplam = 500 ns)
  );
}

void setup() {
  pinMode(13, OUTPUT);  // SCK pini veya başka bir dijital pin
}

void loop() {
  digitalWrite(13, HIGH);  // Pin HIGH yap
  wait500ns();             // 500 ns bekle
  digitalWrite(13, LOW);   // Pin LOW yap
  wait500ns();             // 500 ns bekle
}

 

hmmm...something is not right.... you started by mentioning read operation and checking frequency.
so, where is the read? i see only digitalWrite...

 

hmmm...something is not right.... you started by mentioning read operation and checking frequency.
so, where is the read? i see only digitalWrite...

I did not share the code I read. This code is written by chatgpt that is claimed to be delaying 500ns

 

you can always read or write IO in a loop. but... the question is but what is it exactly that you wish to accomplish? because contents of yours posts are contradictory.

 

Hi mate , I asked 2 questions. First , can I manipulate the spi to do this ?
Secondly , gpt suggest this code for wait less than 1us.
There is nothing contradicts.
"I must be able to differ periods like 28us 26us and more.
Since arduino provides 1us delay at it's shortest , it is very useless for this. "
Here I clearly explained why would I need such a methodology or the gpts function.
I do not ask for the algorithm , I ask for if I can check wheter the signal input is high or low quickly.

 

t

but what is it exactly that YOU need? because contents of yours posts are contradictory:
View attachment 333243
View attachment 333244

this picture that u painted clearly a basic test code about gpts code. I am asking that code makes sense or not

 

syntax looks ok. function is also ok if you need something that generates fixed frequency square wave. if that works for you, great....

 

syntax looks ok. function is also ok if you need something that generates fixed frequency square wave. if that works for you, great....

loop is uninportant part there. if that nop function works , probably with using direct operation through registers , I can read quickly. I need reads around 1us/8 per read.

 

To capture accurate pulse widths, you would set an input to interrupt on change and capture a running timer on each transition. At 16 MHz that would give you 62.5 nsec resolution.

 

To capture accurate pulse widths, you would set an input to interrupt on change and capture a running timer on each transition. At 16 MHz that would give you 62.5 nsec resolution.

yes , to count , I need some delay under microseconds. nop seems reasonable for me

 

yes , to count , I need some delay under microseconds. nop seems reasonable for me

The method I described can count the width of a pulse to the accuracy of one instruction time. You cannot do that with a program loop. Learn how to use timer / counters, they are a powerful feature of the microcontroller.