ESP8266 Interrupt

Other Hardware 3rd Party Boards
1

Hello,
I am trying to get a very simple sketch running, but ...failing :astonished:

I want to measure the frequency with the WEMOD1 mini coming to the pin 4 by external interrupt . The two rising edges are measured so far correct, but I want to get the difference calculated. And this doesn't work...
I am running out of ideas...

volatile unsigned long saveMicros, previousMicros, currentMicros, frequency, duration;

void setup() {
  Serial.begin(115200);
  attachInterrupt(digitalPinToInterrupt(4), IntCallback, RISING);
  delay(10);
}

void loop() {
  Serial.print("prev: ");
  Serial.print(previousMicros);
  Serial.print("  curr:");
  Serial.print(currentMicros);
  Serial.print("  delta:");
  Serial.println(duration);

}

void IntCallback() {
  previousMicros = currentMicros;
  currentMicros = micros();
  duration =  ( previousMicros - currentMicros );
}

And the serial monitor gives results like that:

prev: 7559521 curr:7560820 delta:4294966967 <--- Whaaaat?
prev: 7563423 curr:7565208 delta:4294967016
prev: 7567752 curr:7569254 delta:4294966968
prev: 7571537 curr:7573159 delta:4294967002

2

Current micros is more than previous micros, so answer would be negative. But you're using unsigned long so negative overflows to huge positive. Reverse the order of subtraction

3

Arghh- I did not write my post completely. This is what I have tried before as well. But the results with the changed formula are not correct as well:

prev: 14113243 curr:14114575 delta:34 <--something of 1331 would be right here
prev: 14116795 curr:14118127 delta:35
prev: 14120347 curr:14121680 delta:34
prev: 14123900 curr:14125232 delta:34