Re: Need help with PI PICO...

On 2024-03-25 16:57, The Natural Philosopher wrote:

That is, some asynchrounous event in this sequence
      gpio_put(ULTRASONIC_OUT,1);
     sleep_us(10);
     gpio_put(ULTRASONIC_OUT,0); //reset the input
//if asynch event lasting more than 100uS occurs here...
     // wait for echo pulse start
     while(!gpio_get(ULTRASONIC_IN))
         ;
//then the low-high-low echo pulse will never be detected.

if you change the wait body to include a counter then you could realize that when the counter had reached a high number - you missed the pulse.
Just try again then. Getting a reading is not that time sensitive - or?
:START
       int cnt = 0;
       gpio_put(ULTRASONIC_OUT,1);
       sleep_us(10);
       gpio_put(ULTRASONIC_OUT,0); //reset the input
  //if asynch event lasting more than 100uS occurs here...
       // wait for echo pulse start
       while(TRUE) {
         if (! gpio_get(ULTRASONIC_IN)) {
            cnt++
         } else {
           break;
         }
         if (cnt >= TOO_HIGH_VALUE) {
            goto START;
         }
       }
--
/Björn