lua - NodeMCU gpio triggering incorrectly -

i'm attempting read ir information nodemcu running lua 5.1.4 master build of 8/19/2017.

i might misunderstanding how gpio works , i'm having hard time finding examples relate i'm doing.

pin = 4 pulse_prev_time = 0 ircallback = nil  function trgpulse(level, now)   gpio.trig(pin, level == gpio.high , "down" or "up", trgpulse)    duration = - pulse_prev_time   print(level, duration)    pulse_prev_time = end  function init(callback)   ircallback = callback   gpio.mode(pin, gpio.int)   gpio.trig(pin, 'down', trgpulse) end  -- example print("monitoring ir") init(function (code)   print("omg got something", code) end) 

i'm triggering initial interrupt on low, , alternating low high in trgpulse. in doing i'd expect levels alternate 1 0 in perfect pattern. output shows otherwise:

1   519855430 1   1197 0   609 0   4192 0   2994 1   589 1   2994 1   1198 1   3593 0   4201 1   23357 0   608 0   5390 1   1188 1   4191 1   1198 0   3601 0   3594 1   25147 0   608 1   4781 0   2405 1   3584 0   4799 0   1798 1   1188 1   2994 

so i'm doing wrong or fundamentally don't understand how gpio works. if expected, why interrupts being called multiple times if low/high levels didn't change? , if seem wrong, ideas how fix it?

i'm doing wrong or fundamentally don't understand how gpio works

i suspect it's bit combination of both - latter may cause former.

my explanation may not 100% correct mechanical/electronic perspective (not world) should enough far writing software gpio goes. switches tend bounce between 0 , 1 until settle one. article read on https://www.allaboutcircuits.com/technical-articles/switch-bounce-how-to-deal-with-it/. effect can addressed hardware and/or software.

doing software involves introducing form of delay skip bouncing signals you're interested in "settled state". documented nodemcu lua function use @ https://gist.github.com/marcelstoer/59563e791effa4acb65f

-- inspired https://github.com/hackhitchin/esp8266-co-uk/blob/master/tutorials/introduction-to-gpio-api.md -- , http://www.esp8266.com/viewtopic.php?f=24&t=4833&start=5#p29127 local pin = 4    --> gpio2  function debounce (func)     local last = 0     local delay = 50000 -- 50ms * 1000 tmr.now() has μs resolution      return function (...)         local = tmr.now()         local delta = - last         if delta < 0 delta = delta + 2147483647 end; -- proposed because of delta rolling over, https://github.com/hackhitchin/esp8266-co-uk/issues/2         if delta < delay return end;          last =         return func(...)     end end  function onchange ()     print('the pin value has changed '..gpio.read(pin)) end  gpio.mode(pin, gpio.int, gpio.pullup) -- see https://github.com/hackhitchin/esp8266-co-uk/pull/1 gpio.trig(pin, 'both', debounce(onchange)) 

note: delay empiric value specific sensor/switch!