This tutorial shows how to detect motion with the ESP32 using a PIR motion sensor. In this example, when motion is detected (an interrupt is triggered), the ESP32 starts a timer and turns an LED on for a predefined number of seconds. When the timer finishes counting down, the LED is automatically turned off.
With this example we’ll also explore two important concepts: interrupts and timers.
Before proceeding with this tutorial you should have the ESP32 add-on installed in your Arduino IDE. Follow one of the following tutorials to install the ESP32 on the Arduino IDE, if you haven’t already.
Watch the Video Tutorial and Project Demo
This tutorial is available in video format (watch below) and in written format (continue reading).
Parts Required
To follow this tutorial you need the following parts
- ESP32 DOIT DEVKIT V1 Board – read ESP32 Development Boards Review and Comparison
- Mini PIR motion sensor (AM312) or PIR motion sensor (HC-SR501)
- 5mm LED
- 330 Ohm resistor
- Jumper wires
- Breadboard
You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!
Introducing Interrupts
To trigger an event with a PIR motion sensor, you use interrupts. Interrupts are useful for making things happen automatically in microcontroller programs, and can help solve timing problems.
With interrupts you don’t need to constantly check the current value of a pin. With interrupts, when a change is detected, an event is triggered (a function is called).
To set an interrupt in the Arduino IDE, you use the attachInterrupt() function, that accepts as arguments: the GPIO pin, the name of the function to be executed, and mode:
attachInterrupt(digitalPinToInterrupt(GPIO), function, mode);GPIO Interrupt
The first argument is a GPIO number. Normally, you should use digitalPinToInterrupt(GPIO) to set the actual GPIO as an interrupt pin. For example, if you want to use GPIO 27 as an interrupt, use:
digitalPinToInterrupt(27)With an ESP32 board, all the pins highlighted with a red rectangle in the following figure can be configured as interrupt pins. In this example we’ll use GPIO 27 as an interrupt connected to the PIR Motion sensor.
Function to be triggered
The second argument of the attachInterrupt() function is the name of the function that will be called every time the interrupt is triggered.
Mode
The third argument is the mode. There are 5 different modes:
- LOW: to trigger the interrupt whenever the pin is LOW;
- HIGH: to trigger the interrupt whenever the pin is HIGH;
- CHANGE: to trigger the interrupt whenever the pin changes value – for example from HIGH to LOW or LOW to HIGH;
- FALLING: for when the pin goes from HIGH to LOW;
- RISING: to trigger when the pin goes from LOW to HIGH.
For this 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.
Introducing Timers
In this example we’ll also introduce timers. We want the LED to stay on for a predetermined number of seconds after motion is detected. 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 should use a timer.
The delay() function
You should be familiar with the delay() function as it is widely used. This function is pretty straightforward to use. It accepts a single int number as an argument. This number represents the time in milliseconds the program has to wait until moving on to the next line of code.
delay(time in milliseconds)When you call delay(1000) your program stops on that line for 1 second.
delay() is a blocking function. Blocking functions prevent a program from doing anything else until that particular task is completed. If you need multiple tasks to occur at the same time, you cannot use delay().
For most projects, you should avoid using delays and use timers instead.
The millis() function
Using a function called millis() you can return the number of milliseconds that have passed since the program first started.
millis()Why is that function useful? Because by using some math, you can easily check how much time has passed without blocking your code.
Blinking an LED with millis()
The following snippet of code shows how you can use the millis() function to create a blink LED project. It turns an LED on for 1000 milliseconds, and then turns it off.
/*********
Rui Santos
Complete project details at https://randomnerdtutorials.com
*********/
// constants won't change. Used here to set a pin number :
const int ledPin = 26; // the number of the LED pin
// Variables will change :
int ledState = LOW; // ledState used to set the LED
// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0; // will store last time LED was updated
// constants won't change :
const long interval = 1000; // interval at which to blink (milliseconds)
void setup() {
// set the digital pin as output:
pinMode(ledPin, OUTPUT);
}
void loop() {
// here is where you'd put code that needs to be running all the time.
// check to see if it's time to blink the LED; that is, if the
// difference between the current time and last time you blinked
// the LED is bigger than the interval at which you want to
// blink the LED.
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval) {
// save the last time you blinked the LED
previousMillis = currentMillis;
// if the LED is off turn it on and vice-versa:
if (ledState == LOW) {
ledState = HIGH;
} else {
ledState = LOW;
}
// set the LED with the ledState of the variable:
digitalWrite(ledPin, ledState);
}
}
How the code works
Let’s take a closer look at this blink sketch that works without a delay() function (it uses the millis() function instead).
Basically, this code subtracts the previous recorded time (previousMillis) from the current time (currentMillis). If the remainder is greater than the interval (in this case, 1000 milliseconds), the program updates the previousMillis variable to the current time, and either turns the LED on or off.
if (currentMillis - previousMillis >= interval) {
// save the last time you blinked the LED
previousMillis = currentMillis;
(...)Because this snippet is non-blocking, any code that’s located outside of that first if statement should work normally.
You should now be able to understand that you can add other tasks to your loop() function and your code will still be blinking the LED every one second.
You can upload this code to your ESP32 and assemble the following schematic diagram to test it and modify the number of milliseconds to see how it works.
Note: If you’ve experienced any issues uploading code to your ESP32, take a look at the ESP32 Troubleshooting Guide.
ESP32 with PIR Motion Sensor
After understanding these concepts: interrupts and timers, let’s continue with the project.
Schematic
The circuit we’ll build is easy to assemble, we’ll be using an LED with a resistor. The LED is connected to GPIO 26. We’ll be using the Mini AM312 PIR Motion Sensor that operates at 3.3V. It will be connected to GPIO 27. Simply follow the next schematic diagram.
Important: the Mini AM312 PIR Motion Sensor used in this project operates at 3.3V. However, if you’re using another PIR motion sensor like the HC-SR501, it operates at 5V. You can either modify it to operate at 3.3V or simply power it using the Vin pin.
The following figure shows the AM312 PIR motion sensor pinout.
Uploading the Code
After wiring the circuit as shown in the schematic diagram, copy the code provided to your Arduino IDE.
You can upload the code as it is, or you can modify the number of seconds the LED is lit after detecting motion. Simply change the timeSeconds variable with the number of seconds you want.
/*********
Rui Santos
Complete project details at https://randomnerdtutorials.com
*********/
#define timeSeconds 10
// Set GPIOs for LED and PIR Motion Sensor
const int led = 26;
const int motionSensor = 27;
// Timer: Auxiliary variables
unsigned long now = millis();
unsigned long lastTrigger = 0;
boolean startTimer = false;
boolean motion = false;
// Checks if motion was detected, sets LED HIGH and starts a timer
void IRAM_ATTR detectsMovement() {
digitalWrite(led, HIGH);
startTimer = true;
lastTrigger = millis();
}
void setup() {
// Serial port for debugging purposes
Serial.begin(115200);
// PIR Motion Sensor mode INPUT_PULLUP
pinMode(motionSensor, INPUT_PULLUP);
// Set motionSensor pin as interrupt, assign interrupt function and set RISING mode
attachInterrupt(digitalPinToInterrupt(motionSensor), detectsMovement, RISING);
// Set LED to LOW
pinMode(led, OUTPUT);
digitalWrite(led, LOW);
}
void loop() {
// Current time
now = millis();
if((digitalRead(led) == HIGH) && (motion == false)) {
Serial.println("MOTION DETECTED!!!");
motion = true;
}
// Turn off the LED after the number of seconds defined in the timeSeconds variable
if(startTimer && (now - lastTrigger > (timeSeconds*1000))) {
Serial.println("Motion stopped...");
digitalWrite(led, LOW);
startTimer = false;
motion = false;
}
}
Note: if you’ve experienced any issues uploading code to your ESP32, take a look at the ESP32 Troubleshooting Guide.
How the Code Works
Let’s take a look at the code. Start by assigning two GPIO pins to the led and motionSensor variables.
// Set GPIOs for LED and PIR Motion Sensor
const int led = 26;
const int motionSensor = 27;Then, create variables that will allow you set a timer to turn the LED off after motion is detected.
// Timer: Auxiliar variables
long now = millis();
long lastTrigger = 0;
boolean startTimer = false;The now variable holds the current time. The lastTrigger variable holds the time when the PIR sensor detects motion. The startTimer is a boolean variable that starts the timer when motion is detected.
setup()
In the setup(), start by initializing the Serial port at 115200 baud rate.
Serial.begin(115200);Set the PIR Motion sensor as an INPUT PULLUP.
pinMode(motionSensor, INPUT_PULLUP);To set the PIR sensor pin as an interrupt, use the attachInterrupt() function as described earlier.
attachInterrupt(digitalPinToInterrupt(motionSensor), detectsMovement, RISING);The pin that will detect motion is GPIO 27 and it will call the function detectsMovement() on RISING mode.
The LED is an OUTPUT whose state starts at LOW.
pinMode(led, OUTPUT);
digitalWrite(led, LOW);loop()
The loop() function is constantly running over and over again. In every loop, the now variable is updated with the current time.
now = millis();Nothing else is done in the loop().
But, when motion is detected, the detectsMovement() function is called because we’ve set an interrupt previously on the setup().
The detectsMovement() function prints a message in the Serial Monitor, turns the LED on, sets the startTimer boolean variable to true and updates the lastTrigger variable with the current time.
void IRAM_ATTR detectsMovement() {
Serial.println("MOTION DETECTED!!!");
digitalWrite(led, HIGH);
startTimer = true;
lastTrigger = millis();
}Note: IRAM_ATTR is used to run the interrupt code in RAM, otherwise code is stored in flash and it’s slower.
After this step, the code goes back to the loop().
This time, the startTimer variable is true. So, when the time defined in seconds has passed (since motion was detected), the following if statement will be true.
if(startTimer && (now - lastTrigger > (timeSeconds*1000))) {
Serial.println("Motion stopped...");
digitalWrite(led, LOW);
startTimer = false;
}The “Motion stopped…” message will be printed in the Serial Monitor, the LED is turned off, and the startTimer variable is set to false.
Demonstration
Upload the code to your ESP32 board. Make sure you have the right board and COM port selected.
Open the Serial Monitor at a baud rate of 115200.
Move your hand in front of the PIR sensor. The LED should turn on, and a message is printed in the Serial Monitor saying “MOTION DETECTED!!!”. After 10 seconds the LED should turn off.
Wrapping Up
To wrap up, interrupts are used to detect a change in the GPIO state without the need to constantly read the current GPIO value. With interrupts, when a change is detected, a function is triggered. You’ve also learned how to set a simple timer that allows you to check if a predefined number of seconds have passed without having to block your code.
We have other tutorials related with ESP32 that you may also like:
- ESP32 Web Server – Arduino IDE
- ESP32 Data Logging Temperature to MicroSD Card
- How to Use I2C LCD with ESP32 on Arduino IDE
- ESP32 vs ESP8266 – Pros and Cons
This is an excerpt from our course: Learn ESP32 with Arduino IDE. If you like ESP32 and you want to learn more, we recommend enrolling in Learn ESP32 with Arduino IDE course.
Thanks for reading.
Good Job)
Thank you!
I have this problem, but don’t know how to fix:
load 0x4010f000, len 1384, room 16
tail 8
chksum 0x2d
csum 0x2d
v8b899c12
~ld
ISR not in IRAM!
Hi.
Your callback function needs to be defined in RAM.
For that, use void IRAM_ATTR before the function definition.
Regards,
Sara
hello sara
when i used this command in your motion project,s void setup():
attachInterrupt(digitalPinToInterrupt(motionSensor), detectsMovement, RISING);
i received unknown respanses in my arduino serial monitor that,s run fast and program does not execute.
thanks vm,
areza alikhani
Hi.
Which GPIO are you using to connect the PIR motion sensor?
Make sure that your PIR motion sensor is well connected.
Regards,
Sara
thanks sara
i fixed this problem but i want when motion detect the picture and sms transfered for my phone by 8266 and node-red
thanks vm
hello sara
help me pls for my last post
ISR Best Practice is to do as little as possible inside them. Like only set a flag, ie, FIRED = 1; After the ISR completes and program execution returns back to the main loop(), check the flag, if (FIRED == 1) if TRUE, execute the send “picture and sms “, then clear the flag, FIRED = 0;
Within the ISR, the FIRED flag should probably checked. If it is TRUE, then the ISR was trigger again before the send “picture and sms” code completed.
This is only a problem if the ISR’s continues to get triggered before the main code completes. ISR’s queue up and can exhaust memory, ie, that IRAM.
EXCELLENT ARTICLE!
EXCELENTE ARTIGO, COMO TODOS OUTROS
Thank you Marcio!
Obrigado!
Work for me 100 % Thank you very much !
Thanks 🙂
Can I use 5V triggering for ESP32 pins which operate on 3.3V ?
Hi Ivan.
You can’t do that! The ESP32 pins operate at 3.3V. You can’t provide 5V to those pins – that will damage your ESP32.
Regards,
Sara
Use a resistive devider off of the 5V pin. Use something like
PIR pin-2.2K
2.2K to 3.3K
3.3K to ground
from the junction of the 2.2Kand3.3K connect to the ESP pin.
Hope this helps.
Forrest Erickson
Amused Scientist
Hello great tutorial i got it working but now i am working on a button to activate the system od not, as a alarm system do you have any ideas?
thnx reinier
Hi.
You can add a button and declare it as an interrupt. This button will simply change a variable state to “active” or “not active”.
Then, instead of just looking if motion was detected or not, you also need to check if it is active or not.
So you’ll need a condition that checks the following:
if (motion detected and motion sensor is activated) then do something…
I hope this helps.
Regards,
Sara
Hi, good tutorial. Surprised no one has commented on the little timing mistake for “Blinking an LED with millis()”. You refer to using 1000 milliseconds, but your code has “const long interval = 5000; // interval at which to blink (milliseconds)”. That’s a 4 second difference. Not a big deal. Just an FYI.
Hi Chuck.
Thanks for noticing. We’ve already fixed that.
Regards,
Sara
Hello Thank you for the Tutorial,
i have a question how i can blink the Motion led after motion detected? t i need 10 sec. continuous blinking and after 10 sec. stop the blinking.
Thank you
Hi Ferdi.
I think the best way to do that is by creating two timers, one to keep track of the 10 seconds and the other to blink the LED without delay.
You can find an example to blink the LED without delay in the Arduino examples. In your Arduino IDE, go to File > Examples > 02.Digital > BlinkWithoutDelay
Regards,
Sara
I tried the same code just changed the pins a little bit. I attached an interrupt to gpio27, led on gpio2 and also changed the ON time of led to 1 second in place of 10. But I get error “Guru Meditation Error: Core 1 panic’ed (Interrupt wdt timeout on CPU1) ” but as soon as I disable Serial.begin function things work fine. Any clue why is this happening?
I get an error trying to compile: “expected initializer before ‘detectsMovement'” I’m using a Sparkfun ESP32 Thing. Otherwise everything is as explained in the tutorial. I’ve googled and not been able to find anything for this particular error. Any ideas appreciated, please.
My issue has been resolved. Apparently at some point the board type had reverted back to the default. So the Arduino Uno was selected. With the correct board selected, everything works great.
OK. It is solved now.
Regards,
Sara
Thank you so much for what you do. These tutorials are great.
That’s very weird.
Please make sure that you’ve copied all the code and didn’t delete any line accidentally. Because that’s probably what happened.
Regards,
Sara
Hi Mrs. Sara Santos!
My name is Angel and I bought your book “Learn Esp32 with arduino” and is really good! but in the “Multisensor Project” there is a fatal error in the code:
This Fail says:
‘detectsMovement’ was not declared in this scope
C:\Users\Jhon Kremer\Documents\Arduino\Mando_central\Mando_central.ino: In function ‘void setup()’:
Mando_central:81:55: error: ‘detectsMovement’ was not declared in this scope
attachInterrupt(digitalPinToInterrupt(motionSensor),detectsMovement, RISING);
C:\Users\Jhon Kremer\Documents\Arduino\Mando_central\Mando_central.ino: At global scope:
Mando_central:91:3: error: ‘Serial’ does not name a type
Serial.println(” bytes read from Flash . Values are:”);
^
Mando_central:92:3: error: expected unqualified-id before ‘for’
for(int i = 0; i < EEPROM_SIZE; i++) {
^
Mando_central:92:18: error: 'i' does not name a type
for(int i = 0; i < EEPROM_SIZE; i++) {
^
Mando_central:92:35: error: 'i' does not name a type
for(int i = 0; i < EEPROM_SIZE; i++) {
^
Mando_central:98:10: error: expected constructor, destructor, or type conversion before '(' token
pinMode(output, OUTPUT);
^
Mando_central:99:10: error: expected constructor, destructor, or type conversion before '(' token
pinMode(redRGB, OUTPUT);
^
Mando_central:100:10: error: expected constructor, destructor, or type conversion before '(' token
pinMode(greenRGB, OUTPUT);
^
Mando_central:101:10: error: expected constructor, destructor, or type conversion before '(' token
pinMode(blueRGB, OUTPUT);
^
Mando_central:105:3: error: expected unqualified-id before 'if'
if(!EEPROM.read(0)) {
^
Mando_central:109:3: error: expected unqualified-id before 'else'
else {
^
Mando_central:113:3: error: 'selectedMode' does not name a type
selectedMode = EEPROM.read(1);
^
Mando_central:114:3: error: 'timer' does not name a type
timer = EEPROM.read(2);
^
Mando_central:115:3: error: 'ldrThreshold' does not name a type
ldrThreshold = EEPROM.read(3);
^
Mando_central:116:18: error: expected constructor, destructor, or type conversion before ';' token
configureMode();
^
Mando_central:119:3: error: 'Serial' does not name a type
Serial.print("Connecting to ");
^
Mando_central:120:3: error: 'Serial' does not name a type
Serial.println(ssid);
^
Mando_central:121:3: error: 'WiFi' does not name a type
WiFi.begin(ssid, password);
^
Mando_central:122:3: error: expected unqualified-id before 'while'
while (WiFi.status() != WL_CONNECTED) {
^
Mando_central:127:3: error: 'Serial' does not name a type
Serial.println("");
^
Mando_central:128:3: error: 'Serial' does not name a type
Serial.println("WiFi connected.");
^
Mando_central:129:3: error: 'Serial' does not name a type
Serial.println("IP address: ");
^
Mando_central:130:3: error: 'Serial' does not name a type
Serial.println(WiFi.localIP());
^
Mando_central:131:3: error: 'server' does not name a type
server.begin();
^
Mando_central:132:1: error: expected declaration before '}' token
}
^
Se encontraron varias bibliotecas para "WiFi.h"
Usado: C:\Users\Jhon
No usado: C:\Users\Jhon
No usado: C:\Program
Se encontraron varias bibliotecas para "EEPROM.h"
Usado: C:\Users\Jhon
Se encontraron varias bibliotecas para "DHT.h"
Usado: C:\Users\Jhon
Se encontraron varias bibliotecas para "Adafruit_Sensor.h"
Usado: C:\Users\Jhon
No usado: C:\Users\Jhon
exit status 1
'detectsMovement' was not declared in this scope
I would like that you help me as soon as possible.
I will hope your answer wishing you a have a nice day!
Greetings from México!
PS. I already have installed all "The Libraries", really i don´t know why the code fail it, if i renamed the adafruit librarie and Installed many libraries about this. Thank you!
Hi jhon kremer.
If you have bought the ESP32 course, please post your questions on the RNTLab forum, so that we can reach to you faster: https://rntlab.com/forum/
Cut the detectsMovement() function and paste it before the setup(). I’m talking about the following lines:
void detectsMovement() {
if(armMotion || (armMotion && armLdr)) {
Serial.println(“MOTION DETECTED!!!”);
startTimer = true;
lastMeasure = millis();
}
}
Let me know if this solved your issue. If not, open a new question on the RNTLAB forum. Exclusive for those who have bought the course.
Regards,
Sara
Hi Sara,
Thanks for this – really helpful. When I tried it I sometimes got unexpected results – the LED flashed, or just didn’t stay on for the full time. I made a couple of minor changes that I think helped. Firstly, variables that are used in both the main code and the interrupt I made ‘volatile’:
volatile unsigned long lastTrigger = 0;
volatile boolean startTimer = false;
Secondly, I stopped the interrupt from firing again while the LED was still lit:
void IRAM_ATTR detectsMovement() {
if (!startTimer) {
Serial.println(“MOTION DETECTED!!!”);
digitalWrite(led, HIGH);
startTimer = true;
lastTrigger = millis();
}
}
What do you think?
Best wishes,
Peter
Peter,
From what I’ve read, making shared variables volatile is the right way to handle them, so that there is no chance of using a pre-stored register copy of the variable value, after the variable itself has changed.
Seems like a good practice….still working better?
Dave K.
Hi ,
Is it possible to have the input GPIO on a “master” esp32 and the output GPIO on a “slave” esp32 communicating using esp now?
Hi.
Yes.
Take a look at this tutorial that might help: https://randomnerdtutorials.com/esp-now-two-way-communication-esp32/
Regards,
Sara
Hi Graham,
Have you been able to solve this?
Can you share please?
Regards
Braam
Great code. Been looking for this for some time now. Thanks.
Witam Sara.
Bardzo fajny artykuł.
Jestem pod wrażeniem Twojej wiedzy.
Pozdrawiam Bogdan.
Thanks 🙂
Hi,
Maybe someone else has mentioned it before but I did not find a post about the interrupt types of the ESP32 when used with Arduino.
In this tutorial a list is shown with ESP32 interrupt types but the list is not correct! There are no HIGH or LOW interrupts, HIGH and LOW are equal to TRUE and FALSE, 1 and 0 resp. and should be used for logical purposes, not for interrupts.
By using HIGH or LOW for the interrupt type can lead to unexpected or “faulty” behaviour because HIGH (1) as interrupt type actualy yields an interrupt on the RISING edge and LOW (0) does not correspond to any interrupt type.
Instead of HIGH and LOW, ONHIGH and ONLOW should be used.
Here is are the types for ESP32 as defined in Arduino.h:
RISING 1
FALLING 2
CHANGE 3
ONLOW 4
ONHIGH 5
ONLOW_WE 0x0C
ONHIGH_WE 0x0D
This is realy different from Arduino Uno for instance.
I am just starting with the ESP32 and with some experimenting with pushbuttons and interrupts and it looks like the falling edge of a pulse on a input pin with pull_up resistor, also often triggers the FALLING interrupt on the rising edge of a pulse (debouncing is accounted for). It happens often but not always, when releasing the pushbutton. Even after five seconds or more. I checked the inputpin with my oscilliscope and there are no spikes or debounce pulses shown. Is this a known (erratic) behaviour of the ESP32 ?
Thank you.
Hi!
Thanks for all the suggestions and the good explanations!
Modifying the code slightly, the “lamp” will always light when motion is detected; this may be more like the real world:
if (startTimer && (now – lastTrigger > (timeSeconds*1000)) && !digitalRead (motionSensor))
About IRAM/Instruction RAM: I think it’s not just about the flash being slower, but what effect it has. My understanding is that it must be ensured that all data and functions accessed by an interrupt handler, including those that call the handlers, are in IRAM. If a function or symbol is not properly stored in IRAM and the interrupt handler reads from the flash cache during a flash operation, it will cause a crash.
Thanks.
Rui and Sara, Thank you for the great tutorials. I am really enjoying them and have been telling other people about them.
Thank you so much 😀
You guys at RNT (Rui and Sara) make learning this stuff so much easier than other sites and it comes down to the clear way you present the material. I have long wanted to find out how to use interrupts in my code but thought must be too difficult for me to figure out. But finally I absolutely needed ‘interrupts’ because I have a optical shaft encoder to read and the speed it runs means that normal code is not going to cut it. So I first watched the video then followed along with the code explanations and got the idea instantly. There was simply nothing in the code that I did not understand except IRAM_ATTR. But you even explained that. As a 70 year old learning this stuff from scratch I feel so empowered by this new knowledge and understanding and that is down to you guys.
That’s great!
I’m really glad you learned with our tutorials.
Thank you for following our work.
Regards,
Sara
I have a Wemos D1 Mini with a motion sensor connected to it. I would like to add a LED of 5v to it so if the montion sensor detects movement the led will stay ON for 60 seconds.
For now I have this:
binary_sensor:
– platform: gpio
pin: GPIO12
name: “PIR Sensor”
device_class: motion
Is it possible to use the same Wemos to power the 5v led?
Where do I need to connect the LED and what do I have to add to the code?
You should always avoid putting a Serial.println statement inside an isr interrupt handler.
Serial.println(“MOTION DETECTED!!!”);
This statement was causing my ESP32 to reboot sometimes when the isr was executed.
Once I commented this statement out, all OK.
Discussion here https://esp32.com/viewtopic.php?f=13&t=3748&p=17131
I forgot to mention you can replace the Serial.println statement with an isr safe print statement ets_printf()
This small change eliminated the rebooting issue
//Serial.println(“MOTION DETECTED!!!”);
ets_printf(“MOTION DETECTED!!!\n”);
Thanks for sharing that.
Regards,
Sara
Hi There,
What do you suggest for implementing the timer in assembly (directly in ESP32)?
Thanks
hey there i need some help i want to connect another led TO GPIO25 that switches on and of after led GPIO26 and switches on just before GPIO26 switchs off
please help with code
The persistent popup advert for your books is VERY annoying. I have purchased the books of interest to me and continually having to be interrupted and close this advert is irritating. Maybe look at some other strategy as it is not up to the standard of your excellent website.
Hi.
I’m sorry for that issue.
If you login into your browser and use your account, for example using your google account on google chrome, it will save that on cache and it will only display it the first three times.
Regards,
Sara
Hello Random Nerd, excellent article, as usual.
Using timer for the first time with esp32 and following your article, works real good until I enable esp-now ( or the wifi ) .
is it possible to get a precise timer running with the WiFi ( or esp-now ) ??
if yes , how.
tks
Hi.
Yes.
The Wi-Fi should not interfere with the timers.
Regards,
Sara
tks for the reply Sara as ‘ The Wi-Fi should not interfere with the timers’
Altough, I see otherwise.
Will continue my search
Do you have a sample code that uses timers and wifi ?
Unfortunately, we don’t have any tutorials dedicated specifically to that subject.
Regards,
Sara
Hi sara,
Which GPIO pin on ESP32 board to connect the PIR motion sensor?
Hi.
We’re using GPIO 27. But, you can use any other suitable GPIO.
Check the ESP32 pinout: https://randomnerdtutorials.com/esp32-pinout-reference-gpios/
Regards,
Sara