ESP8266 Community Forum

- Thu Oct 13, 2016 1:01 am #56447 I am trying to use timers to blink some LEDs. However, I don't know how to pass an argument to the callback function to specify which pin to turn off. Here is some example code that doesn't work.

for pin in pairs(devices) do
myTimer = tmr.create()
tmr.alarm(myTimer, 5000, tmr.ALARM_SINGLE, function(myTimer, pin) print(pin) end)
end

Do I have to have a separately hardcoded timer for each pin, or can I do this in a way that lets me assign pins somewhere else, and dynamically create timers for them?

- Sun Oct 23, 2016 8:15 am #56978

I don't know how to pass an argument to the callback function

You need an intermediary function which takes that parameter and returns a closure:

Code: Select allfunction createCallback(which_pin)
  -- optional: local pin = which_pin
  return function()
    print(which_pin) -- or 'pin', see above
  end
end
for pin = 1, 10 do
  myTimer = tmr.create()
  tmr.alarm(myTimer, 5000, tmr.ALARM_SINGLE, createCallback(pin))
end


Reference: http://www.luafaq.org/#T1.28.1

https://frightanic.com/
https://nodemcu-build.com/
https://github.com/marcelstoer/nodemcu-pyflasher