ESP8266 Community Forum

- Sat Apr 09, 2016 3:38 pm #45192 A very big thanks again, Terry!

This time it seems to work! I fixed some minor typos in your code and that was it. The only thing I figured out was that the first measurement is usually off (the time is always to low). That's why I excluded it from the result/average calculation.

Here is the final code (without code cleanup/optimization and removal of debug statements):

Code: Select alllocal gpio, time_start, time_end, trigger, echo = gpio, 0, 0
local sample_count, timer_id

return function(trig_pin, echo_pin, sample_cnt, timer_id, report_cb)
    trigger, echo   = trig_pin or 7, echo_pin or 6
    sample_count, timer_id = (sample_cnt+1) or 4, timer_id or 1   

    local total, i, result = 0, 0, {}

    local function echo_cb(level)
      if level == 1 and result[i] == 0 then
        result[i] = -tmr.now()
        gpio.trig(echo, "down")
      elseif level == 0 and result[i] < 0 then
        result[i] = tmr.now() + result[i];
        gpio.trig(echo, "none")
      else
        gpio.trig(echo, "none") -- anything else turn off interrupts and restart at next sample
        print("DEBUG INT off")
      end
    end
   
    local function measure()
      if i > 0 then -- process last sample
        if result[i] < 0 then 
          result[i] = 0
          i = i - 1
          return -- skip a beat to allow the sonar to settle down
        else
          total = total + result[i];
        end
        if i == sample_count then
          tmr.unregister(timer_id)
          for j = 1, sample_count do print(("Sample %u is %u"):format(j,result[j])) end
          total = total - result[1] -- substract sample one because it is usually off...
          return report_cb(total / (58*(sample_count-1)))
        end
      end

      gpio.mode(echo, gpio.INT)
      gpio.trig(echo, "up", echo_cb)
      gpio.write(trigger, gpio.HIGH); tmr.delay(20); gpio.write(trigger, gpio.LOW)
      i = i + 1
    end
   
    for j = 0, sample_count do result[j] = 0 end -- pre-allocate result array

    gpio.mode(trigger, gpio.OUTPUT)
    tmr.alarm(timer_id, 60, tmr.ALARM_AUTO, measure)
    measure()
  end

Again, thank you very much for your support, Terry!

- Sat Apr 09, 2016 5:59 pm #45199 Thanks to you as well, lepido. I will probably use these myself.

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