NodeMCU Learning (IV)--LED Control

1. Schematic diagram

2. GPIO definition

3. Case 1: Light up the LED

(1) GPIO-related APIs, see the official documentation

(2) API--gpio.mode()

(3) API--gpio.write()

(4) Light up the LED on the module

pin = 4

gpio.mode(pin, gpio.OUTPUT)

gpio.write(pin, gpio.LOW)

4. Case 2: Implement LED flashing

pin=4 -- 4 is D4, GPIO2

flag=1

timer1 = tmr.create()

gpio.mode(pin, gpio.OUTPUT)

gpio.write(pin, gpio.HIGH) 

function run_led() 

    if flag == 1 then

        gpio.write(pin, gpio.LOW)

        flag = 0

    else

        gpio.write(pin, gpio.HIGH)  

        flag = 1

    end      

end

timer1:alarm(1000, tmr.ALARM_AUTO, run_led)

5. Notes

(1) NodeMCU modules are produced by multiple manufacturers, and the schematics of different manufacturers may be different, so before writing code, you must carefully read the schematic corresponding to the module you have, and do not search online; (I made this mistake, which resulted in the effect not being achieved, and then I was depressed for several hours because of whether there was a problem with the code);

(2) In the GPIO API function, the pin uses the serial number value corresponding to the GPIO. For example, the serial number corresponding to GPIO16 is 0, and the serial number corresponding to GPIO2 is 4.

(3) The API functions in the Chinese documentation of the NodeMCU API obtained online are very different from the API actually used now. It is recommended to check the API directly on the official website;