NODEMCU LUA SIMPLE DELAY CODE

The value will quickly become too large for an int to store Generally, you should use 'unsigned long' for variables that hold time

Int ledState = LOW // ledState used to set the LED Used here to set a pin number :Ĭonst int ledPin = 26 // the number of the LED pin It turns an LED on for 1000 milliseconds, and then turns it off.

NODEMCU LUA SIMPLE DELAY CODE

The following snippet of code shows how you can use the millis() function to create a blink project. If you’re already familiar with timers, you can skip to the PIR motion sensor project. If you’re not familiar with millis() function, we recommend reading this section. Blinking an LED using millis() (without delay) Why is that function useful? Because by using some math, you can easily verify how much time has passed without blocking your code. Using a function called millis() you can return the number of milliseconds that have passed since the program first started. For most projects you should avoid using delays and use timers instead. If you need multiple tasks to occur at the same time, you cannot use delay(). Blocking functions prevent a program from doing anything else until that particular task is completed. When you call delay(1000) your program stops on that line for 1 second. This number represents the time in milliseconds the program has to wait until moving on to the next line of code. The delay() function accepts a single int number as an argument. Instead of using a delay() function that blocks your code and doesn’t allow you to do anything else for a determined number of seconds, we’ll use a timer. We want the LED to stay on for a predetermined number of seconds after motion is detected. Introducing ESP8266 Timersįor this tutorial, we’ll use timers. RISING: to trigger when the pin goes from LOW to HIGH.įor our example, will be using the RISING mode, because when the PIR motion sensor detects motion, the GPIO it is connected to goes from LOW to HIGH.FALLING: for when the pin goes from HIGH to LOW.

CHANGE: to trigger the interrupt whenever the pin changes value – for example from HIGH to LOW or LOW to HIGH.

The third argument is the mode and there are 3 different modes: ISRs need to have ICACHE_RAM_ATTR before the function definition to run the interrupt code in RAM. The best approach is to signal the main code that the interrupt has happened by using a global variable and within the loop() check and clear that flag, and execute code. The ISR function should be as simple as possible, so the processor gets back to the execution of the main program quickly. The second argument of the attachInterrupt() function is the name of the function that will be called every time the interrupt is triggered – the interrupt service routine (ISR). The ESP8266 supports interrupts in any GPIO, except GPIO16. For example, if you want to use GPIO 14 as an interrupt, use: digitalPinToInterrupt(14) You should use digitalPinToInterrupt(GPIO) to set the actual GPIO as an interrupt pin. To set an interrupt in the Arduino IDE, you use the attachInterrupt() function, that accepts as arguments: the GPIO interrupt pin, the name of the function to be executed, and mode: attachInterrupt(digitalPinToInterrupt(GPIO), ISR, mode) GPIO interrupt pin This is especially useful to trigger an action whenever motion is detected or whenever a pushbutton is pressed without the need to constantly check its state. When an interrupt happens, the processor stops the execution of the main program to execute a task, and then gets back to the main program as shown in the figure below. This function is called interrupt service routine (ISR). When a change is detected, an event is triggered – a function is called. With interrupts you don’t need to constantly check the current pin value. Interrupts are useful for making things happen automatically in microcontroller programs and can help solve timing problems. Follow this tutorial to Install ESP8266 in Arduino IDE, if you haven’t already. attachInterrupt(digitalPinToInterrupt(GPIO), ISR, mode) īefore proceeding with this tutorial you should have the ESP8266 add-on installed in your Arduino IDE. The mode can be CHANGE, RISING or FALLING. The ISR function must have the ICACHE_RAM_ATTR attribute declared. To create an interrupt, call attachInterrupt() and pass as arguments the GPIO interrupt pin, the ISR (funcion to be called) and mode. When the timer finishes counting down, the LED automatically turns off. As an example, we’ll detect motion using a PIR motion sensor: when motion is detected, the ESP8266 starts a timer and turns an LED on for a predefined number of seconds.

Nodemcu lua simple delay