FreqMeasure on Uno using ICP1/ICR1 doesn't appear to work.

[drf5n]

Describe the bug
The ICP1/ICR1 feature doesn't appear to work with the FreqMeasure library on a Simulated Uno while it does on silicon.

Here is a sketch demonstrating it:

https://wokwi.com/projects/330562550517203540

For an Uno, FreqMeasure monitors Timer1 per:

https://github.com/PaulStoffregen/FreqMeasure/blob/8d4485f7f439267f0a9236999bff4f232d8a83dd/util/FreqMeasureCapture.h#L29

The register code that FreqMeasure uses on an Uno is:

https://github.com/PaulStoffregen/FreqMeasure/blob/8d4485f7f439267f0a9236999bff4f232d8a83dd/util/FreqMeasureCapture.h#L393-L435

To Reproduce
Steps to reproduce the behavior, including link to a simulation project where we can see the problem.

Use the demo sketch from https://www.pjrc.com/teensy/td_libs_FreqMeasure.html

I added an analogOut(3,127); to make the Uno self-testing. Here's a sketch and code:

https://wokwi.com/projects/330562550517203540

/*
This is a demo of the FreqMeasure library 

On an Uno, jumpering pin 3 to pin 8 reports the PWM frequency of 490.20Hz

490.20
490.20
490.20
490.20
490.20
...

With the pin floating with a loose jumper it reports 60Hz hum.  
It does not report with pin 8 grounded.

On Wokwi this doesn't appear to work.  
I reported this as https://github.com/wokwi/wokwi-features/issues/352

Code: https://wokwi.com/projects/330562550517203540

This is a modificaton of the https://www.pjrc.com/teensy/td_libs_FreqMeasure.html demo code
to add a PWM output on pin 3.

It adds some code to track pin 8;

With the jumper to pin 13 and the switch, you can see the pwm output on the built-in LED and toggle 
the connection.


*/
#include <FreqMeasure.h> // https://www.pjrc.com/teensy/td_libs_FreqMeasure.html

void setup() {
  Serial.begin(115200);
  FreqMeasure.begin();
  pinMode(3,OUTPUT); analogWrite(3,127);  // 50% duty cycle on pin 3
}

double sum=0;
int count=0;
static uint32_t count8=0;

void loop() {
  if (FreqMeasure.available()) {
    // average several reading together
    sum = sum + FreqMeasure.read();
    count = count + 1;
    if (count > 30) {
      float frequency = FreqMeasure.countToFrequency(sum / count);
      Serial.println(frequency);
      sum = 0;
      count = 0;
    }
  }
  count8 += digitalRead(8)==LOW;
  report();
}

void report(){
  static uint32_t last = -1000;
  if(millis() - last >= 1000){
    last+=1000;
    Serial.print("count8: ");
    Serial.println(count8); 
  }
}

Expected behavior

The same sketch on a silicon Uno with a jumper from 3 to 8 produces this output:

490.20
490.20
490.20
490.20
490.20
490.20
490.20
490.20
490.20

I would expect the simulation to behave similarly.
Environment (please complete the following information):

• OS: iOS
• Browser chrome
• Version 100.0.4896.127 (Official Build) (x86_64)

Additional context

[urish]

Thanks for the super detailed report!

I looked into this, and the reason for this issue is that we're missing the Input Capture unit in the timers. Opened wokwi/avr8js#125 to track it.