From: Pancho.Jones@proton.me   
      
   On 30/03/2024 09:17, The Natural Philosopher wrote:   
   > On 30/03/2024 02:04, Jim H wrote:   
   >> On Fri, 29 Mar 2024 10:49:13 +0000, in ,   
   >> The Natural Philosopher  wrote:   
   >>   
   >>> Maybe ascii art will help   
   >>>   
   >>> CONTROL=10µs   
   >>> ____| |________   
   >>>   
   >>> RETURN = wahatever   
   >>> _____|^^^^^^^^^^^^|____________   
   >>>   
   >>   
   >> Assuming my bleary-eyed math is correct, 10µs is the length of one   
   >> cycle of ultrasound at 100,000 Hz.   
   >>   
   > The width of that pulse is pretty much immaterial - its only a digital   
   > trigger, It doesn't send anything directly.   
   >   
   > The unit does that, and senses a high to the output. Then it transmits a   
   > squawk., When it receives an echo it switches that to low.   
   >   
   > Its a smart device .   
   >   
      
   I think that is the part I was missing. I assumed it was like an analog   
   device, out pin was for send  and the in pin signalled it was receiving.   
      
   On reflection, the code makes sense if it is a smart device. The in pin   
   just goes high (or low) for the period between sending and receiving a   
   few micro seconds of the echo.   
      
      
   > https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf   
   >   
      
   Not the most precise wording.   
      
   Having taken the trouble to understand. I might buy one to tell me if my   
   garage door is open. Buy an echo device that is, not a PICO.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)