ESP32 NodeMCU Basic Interface Examples

 Here we can see ESP32 NodeMCU Basic Interface Examples

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LED glow using Button Input Method in While loop

gpio.config( { gpio=23, dir=gpio.OUT }, { gpio=0, dir=gpio.IN}) 
while(true)
do
   if (gpio.read(0)==0) then gpio.write(23, 1) 
   else gpio.write(23, 0) 
   end 
end

LED glow using Button Interrupt

gpio.trig(0, gpio.INTR_UP_DOWN,pin_interrupt_1) –GPIO-0 as INPUT
function pin_interrupt_1(level)
if (0 == gpio.read(0)) then
gpio.write(23, 1)
else
gpio.write(23, 0)
end
end

LED Blink using Timer

gpio.config( { gpio=23, dir=gpio.OUT }) 
ArunEworld_timer = tmr.create()
 ArunEworld_timer:register(1000, tmr.ALARM_AUTO, function() 
	if (gpio.read(23)==1) then gpio.write(23, 0)
	elseif (gpio.read(23)==0) then gpio.write(23, 1)
	end
 end)
ArunEworld_timer:start()

GPIO Configuration

gpio.config({ gpio=23, dir=gpio.OUT })

• gpio=23 → This selects GPIO 23 on the ESP32/NodeMCU.
• dir=gpio.OUT → Sets the pin as an output pin.
• Effect: You can now control GPIO 23 programmatically by writing HIGH (1) or LOW (0) values.

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Creating a Timer

ArunEworld_timer = tmr.create()

• tmr.create() → Creates a new software timer object.
• ArunEworld_timer → Stores this timer, so it can be started, stopped, or reused.

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Registering the Timer Callback

ArunEworld_timer:register(1000, tmr.ALARM_AUTO, function() 
	if (gpio.read(23)==1) then 
		gpio.write(23, 0)
	elseif (gpio.read(23)==0) then 
		gpio.write(23, 1)
	end
end)

• 1000 → Timer interval in milliseconds (1000 ms = 1 second).
• tmr.ALARM_AUTO → Timer repeats automatically after each interval.
• function() ... end → The callback function executed every 1 second.

Inside the callback:

• gpio.read(23) → Reads the current state of GPIO 23.
• if 1 then gpio.write(23,0) → If the pin is HIGH, set it LOW.
• elseif 0 then gpio.write(23,1) → If the pin is LOW, set it HIGH.

Effect: This toggles GPIO 23 every second. If you connect an LED to GPIO 23, it will blink with a 1-second interval.

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Starting the Timer

ArunEworld_timer:start()

Activates the timer, so the callback function begins executing repeatedly every 1 second. ESP32 NodeMCU Basic Interface Examples.

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