A little more help on smartpins

Comments

• AJL Posts: 521

  2019-12-05 02:13 edited 2019-12-05 02:17

  You aren't monitoring the IN bit for the smartpin in question.
  I think you'll find that with no edges to time, the Z register (which holds the result) will still give you the result of the last completed measurement, but the IN bit will be low.
  
  If you tested INA[7] before RDPIN you'd know whether the Z register contents was current or stale. Simply waiting for a new reading won't achieve what you want so you need to keep looping and detect valid new readings and act accordingly.
  
  As your loop could easily cycle more than once per pulse you need to keep track of this in a variable.
  
  It could be something as crude as

  repeat
      if ina[7] == 0                'new count available?
          stalecount++           'no 
      elseif
          stalecount := 0       'yes, clear stalecount and get it
          asm
            rdpin    tmr1, #7 {wc}
          endasm
  
      if stalecount > toolong  ' reading is too old, so pulse train has been lost
          tmr1 := 0
  
    serial.str(string(" Tmr "))  
    serial.dec(tmr1)
    serial.str(string("     ")) 
  
  

  
  Finding a value for toolong might need some trial and error, or some cycle counting based on the final code.
  
  EDIT: Of course, the whole status testing, stale count tracking, and pin reading could be done in asm, but the serial object timing is the timing wildcard.
• CRST1 Posts: 106

  2019-12-05 02:25 edited 2019-12-05 02:30

  Can you tell me what sets the ina to 0? Is it when read with rdpin?
  I take it it's set to 1 when it reads a complete pulse from rise to rise. then what sets it low again?
  
  The reason for this is to read a speed and tach pulse train for a vehicle.
• evanh Posts: 16,870

  2019-12-05 02:41 edited 2019-12-05 02:44

  From the main google doc, at beginning of smartpins:

  When a mode-related event occurs in a smart pin, it raises its IN signal to alert the cog(s) that new data is ready, new data can be loaded, or some process has finished. A cog acknowledges a smart pin whenever it does a WRPIN, WXPIN, WYPIN, RDPIN or AKPIN on it. This causes the smart pin to lower its IN signal so that it can be raised again on the next event. Note that since the RQPIN instruction (read quiet) does not do an acknowledge, it can be used by any number of cogs, concurrently, to read a pin without bus conflict.

  
  And for mode %10011:

  Upon completion of X periods, the measurement is placed in Z, IN is raised, and a new measurement begins. RDPIN/RQPIN can then be used to retrieve the completed measurement. Z will be limited to $80000000.

  
  So, yep, your hunches are all correct.
  
  
• CRST1 Posts: 106

  2019-12-05 02:52

  Thanks. I guess I read that, I have those parts printed, it's just so much new to learn and I don't injest it when I'm just reading it. I will probably have more questions, especially when I get into the analog to digital stuff. I'll try the ina monitor and let you guys know how it comes out.
• CRST1 Posts: 106

  2019-12-05 03:38

  Update
  Yes that will work. I had tried similar before but was using clock values for the counter loop. It was way too long of loop and never reset to 0. Brought the number way down and now it works with the too long counter.
  It's been a long three days of studying but its getting there.
  Thank you
  
• AJL Posts: 521

  2019-12-05 06:11

  CRST1 wrote: »

  Update
  Yes that will work. I had tried similar before but was using clock values for the counter loop. It was way too long of loop and never reset to 0. Brought the number way down and now it works with the too long counter.
  It's been a long three days of studying but its getting there.
  Thank you

  
  Glad to be of help. Living is learning, or at least it should be.