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Basics: Project 072l

Project name: ESP32 Development board - PIR sensor module

Tags: ESP32 Dev Module, ESP32 development board, ESP32 Development board with WiFi and Bluetooth, ESP32-DevKitC V4 development board, ESP-WROOM-32 module with ESP32‑D0WDQ6 chip, Espressif Systems, ESP32-based development board, ESP32 modules, ESP32-WROOM-32, ESP32-WROOM-32U, ESP32-WROOM-32D, ESP32-SOLO-1, USB-UART bridge, IOT, ESP-WROOM-32 Dev Module, ESP32 DEVKITV1, Installing the ESP32 Board in Arduino IDE, Uploading sketch, PIR motion sensor, HC-SR505 Mini PIR Motion Sensor, Mini PIR Motion Sensor Module SC0322, PIR motion sensor HC-SR501

Attachments: sketch, sketch1

In this project, you need these parts :

1. ESP32 development board with WiFi and Bluetooth and USB A / micro USB B cable 1 pc

2.Arduino IDE ( you can download it from here  )

3.Mini PIR Motion Sensor Module SC0322 1pc

4. Jumper cables F-M

5. Breadboard 1 pc

6. LED 1 pc

7. Resistor 220 Ohm 1 pc

General

We will learn how to use PIR sensor module with the ESP32 development board and explore interrupts and timers.

There are a lot of different development boards made. You can find more information about them here. 

Interrupts

We use interrupts to trigger an event with a PIR motion sensor. Interrupts are very useful for making things happen automatically in Arduino projects and can help solve timing problems. With interrupts you do not need constantly check the current value of a pin - when a change detected an event triggers (a function called). We use attachInterrupt() function to set an interrupt in the Arduino IDE which accepts as arguments: the GPIO pin, the name of the function to be executed and mode: attachInterrupt(digitalPinToInterrupt(GPIO), function, mode); The first argument is a GPIO number. For example, if you want to use GPIO 26 as an interrupt: digitalPinToInterrupt(26). All selected with red pins can be configured as interrupt pins. In this project we will use GPIO 26 as an interrupt connected to the PIR Motion sensor.

The second argument of the attachInterrupt() function is the name of the function that will be called every time the interrupt triggered.

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.

Timers

In this project we will also use timers. We want the LED to stay on for a set number of seconds after motion detected.

You should be familiar with the delay() function as it is widely used. This function is pretty straight forward 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). delay() is a blocking function and prevents a program from doing anything else until that particular task 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.

Using a function called millis() you can return the number of milliseconds that have passed since the program first started without blocking your code. The following sketch shows how you can use the millis() function (blink LED project). It turns an LED on for 1000 milliseconds, and then turns it off.

Understanding PIR sensor module

You can read more about it here.

Understanding the ESP32 Development board with WiFi and Bluetooth

We will discuss here an Espressif Systems products. Our development board is using ESP-WROOM-32 module from Espressif Systems.

Espressif offers a wide range of fully-certified Wi-Fi & BT modules powered by their own advanced SoCs.

1. Dual-core Modules with Wi-Fi & Dual-mode Bluetooth

Features

• Two independently-controlled CPU cores with adjustable clock frequency, ranging from 80 MHz to 240 MHz
• +19.5 dBm output at the antenna ensures a good physical range
• Classic Bluetooth for legacy connections, also supporting L2CAP, SDP, GAP, SMP, AVDTP, AVCTP, A2DP (SNK) and AVRCP (CT)
• Support for Bluetooth Low Energy (BLE) profiles including L2CAP, GAP, GATT, SMP, and GATT-based profiles like BluFi, SPP-like, etc
• Bluetooth Low Energy (BLE) connects to smart phones, broadcasting low-energy beacons for easy detection
• Sleep current is less than 5 μA, making it suitable for battery-powered and wearable-electronics applications
• Integrates 4 MB flash
• Peripherals include capacitive touch sensors, Hall sensor, low-noise sense amplifiers, SD card interface, Ethernet, high-speed SPI, UART, I2S and I2C
• Fully certified with integrated antenna and software stacks

2. Single-core Modules with Wi-Fi & Dual-mode Bluetooth

Features

• High-performance 160 MHz single-core CPU
• +19.5 dBm output at the antenna ensures a good physical range
• Classic Bluetooth for legacy connections, also supporting L2CAP, SDP, GAP, SMP, AVDTP, AVCTP, A2DP (SNK) and AVRCP (CT)
• Support for Bluetooth Low Energy (BLE) profiles including L2CAP, GAP, GATT, SMP, and GATT-based profiles like BluFi, SPP-like, etc
• Bluetooth Low Energy (BLE) connects to smart phones, broadcasting low-energy beacons for easy detection
• Sleep current is less than 5 μA, making it suitable for battery-powered and wearable-electronics applications
• Peripherals include capacitive touch sensors, Hall sensor, low-noise sense amplifiers, SD card interface, Ethernet, high-speed SPI, UART, I2S and I2C
• Fully certified with integrated antenna and software stacks

3. Single-core Modules with 802.11b/g/n 2.4 GHz Wi-Fi

Features

• High-performance 160 MHz single-core CPU
• +19.5 dBm output at the antenna ensures a good physical range
• Sleep current is less than 20 μA, making it suitable for battery-powered and wearable-electronics applications
• Peripherals include UART, GPIO, I2C, I2S, SDIO, PWM, ADC and SPI
• Fully certified with integrated antenna and software stacks

There are different development Boards made by Espressif Systems and other manufacturers. We will publish some information about Espressif Systems boards but you can also find out more information about other development boards here.

1. 2.4 GHz Wi-Fi & BT/BLE Development Boards

Features

• PC connectivity: USB
• Power supply options: USB (by default), or 5V/GND header pins, or 3V3/GND header pins
• SDK: ESP-IDF source code and example applications

2. 2.4 GHz Wi-Fi Development Boards

Features

• PC connectivity: USB
• SDK: ESP8266 SDK source code and example applications

3. 2.4 GHz Wi-Fi + BT/BLE + Sensor Development Boards

Features

• PC connectivity: USB
• SDK: ESP-IOT-SOLUTION source code and example applications

You can find more information (datasheets, schematics, pins descriptions, functional desgn descriptions) about each board by pressing Getting started link close to each board here.

ESP32 chip

ESP32 is a series of low cost, low power system on a chip microcontrollers with integrated Wi-Fi and dual-mode Bluetooth. The ESP32 series employs a Tensilica Xtensa LX6 microprocessor in both dual-core and single-core variations and includes in-built antenna switches, RF balun, power amplifier, low-noise receive amplifier, filters, and power management modules. ESP32 is created and developed by Espressif Systems, a Shanghai-based Chinese company, and is manufactured by TSMC using their 40 nm process. It is a successor to the ESP8266 microcontroller.

ESP32 can perform as a complete standalone system or as a slave device to a host MCU, reducing communication stack overhead on the main application processor. ESP32 can interface with other systems to provide Wi-Fi and Bluetooth functionality through its SPI / SDIO or I2C / UART interfaces.

ESP32 is highly-integrated with in-built antenna switches, RF balun, power amplifier, low-noise receive amplifier, filters, and power management modules. ESP32 adds priceless functionality and versatility to your applications with minimal Printed Circuit Board (PCB) requirements.

ESP32 is capable of functioning reliably in industrial environments, with an operating temperature ranging from –40°C to +125°C. Powered by advanced calibration circuitries, ESP32 can dynamically remove external circuit imperfections and adapt to changes in external conditions.

Engineered for mobile devices, wearable electronics and IoT applications, ESP32 achieves ultra-low power consumption with a combination of several types of proprietary software. ESP32 also includes state-of-the-art features, such as fine-grained clock gating, various power modes and dynamic power scaling.

Functional Block Diagram:

Features of the ESP32 include the following:

Processors:

• CPU: Xtensa dual-core (or single-core) 32-bit LX6 microprocessor, operating at 160 or 240 MHz and performing at up to 600 DMIPS
• Ultra low power (ULP) co-processor
• Memory: 520 KiB SRAM

Wireless connectivity:

• Wi-Fi: 802.11 b/g/n
• Bluetooth: v4.2 BR/EDR and BLE

Peripheral interfaces:

• 12-bit SAR ADC up to 18 channels
• 2 × 8-bit DACs
• 10 × touch sensors (capacitive sensing GPIOs)
• Temperature sensor
• 4 × SPI
• 2 × I²S interfaces
• 2 × I²C interfaces
• 3 × UART
• SD/SDIO/CE-ATA/MMC/eMMC host controller
• SDIO/SPI slave controller
• Ethernet MAC interface with dedicated DMA and IEEE 1588 Precision Time Protocol support
• CAN bus 2.0
• Infrared remote controller (TX/RX, up to 8 channels)
• Motor PWM
• LED PWM (up to 16 channels)
• Hall effect sensor
• Ultra low power analog pre-amplifier

Security:

• IEEE 802.11 standard security features all supported, including WFA, WPA/WPA2 and WAPI
• Secure boot
• Flash encryption
• 1024-bit OTP, up to 768-bit for customers
• Cryptographic hardware acceleration: AES, SHA-2, RSA, elliptic curve cryptography (ECC), random number generator (RNG)

Power management:

• Internal low-dropout regulator
• Individual power domain for RTC
• 5uA deep sleep current
• Wake up from GPIO interrupt, timer, ADC measurements, capacitive touch sensor interrupt

You can find ESP32 chip datasheet here, hardware design here, technical reference manual here.

Signals and connections of the PIR sensor module

We are goinig to use Mini PIR Motion Sensor Module SC0322 in this project.

Signals and connections of the ESP32 Development board with WiFi and Bluetooth

You can find more information (datasheets, schematics, pins descriptions, functional desgn descriptions) about each board (made by Espresiff Systems) by pressing Getting started link close to each board here.

Let's check our development board - ESP32 DEVKITV1 with ESP-WROOM-32 module from Espressif Systems:

Pinout diagram for the ESP Wroom 32 breakout:

ESP32-WROOM-32 - ESP32-WROOM-32 module soldered to the development board. Optionally ESP32-WROOM-32D, ESP32-WROOM-32U or ESP32-SOLO-1 module may be soldered instead of the ESP32-WROOM-32.

USB-UART Bridge - A single chip USB-UART bridge provides up to 3 Mbps transfers rates.

BOOT button - Download button: holding down the Boot button and pressing the EN button initiates the firmware download mode. Then user can download firmware through the serial port.

EN button - Reset button: pressing this button resets the system.

Micro USB Port - USB interface. It functions as the power supply for the board and the communication interface between PC and the ESP module.

TX0, TX2 - transmit pin. GPIO pin

RX0, RX2  - receive pin.  GPIO pin

3V3 (or 3V or 3.3V) - power supply pin (3-3.6V). 

GND - ground pin.

EN - Chip enable. Keep it on high (3.3V) for normal operation.

Vin - External power supply 5VDC.

Wiring

Step by Step instruction

The ESP32 is currently being integrated with the Arduino IDE like it was done for the ESP8266. There’s an add-on for the Arduino IDE that allows you to program the ESP32 using the Arduino IDE and its programming language.

1. Download and install the latest Arduino IDE Windows Installer from arduino.cc
2. Download and install Git and Git GUI from git-scm.com
3. Search for Git GUI, right-click the icon and select “Run as administrator“
4. 
5. Select the Clone Existing Repository option.
6. 
7. Select source and destination. Source Location: https://github.com/espressif/arduino-esp32.git
8. Target Directory:C:/Users/[YOUR_USER_NAME]/Documents/Arduino/hardware/espressif/esp32
9. Do not create the espressif/esp32 folders, because they will be created automatically.
10. 
11. Click Clone to start cloning the repository.Wait a few seconds while the repository is being cloned.
12. 
13. 
14. Open the folder: C:/Users/[YOUR_USER_NAME]/Documents/Arduino/hardware/espressif/esp32/tools
15. Right-click the get.exe file and select “Run as administrator“.
16. 
17. You will see that necessary files will be downloaded and upzipped. It will take some time.
18. 
19. When get.exe finishes, you should see the following files in the directory.
20. 
21. Plug the ESP32 development board to your PC and wait for the drivers to install (or install manually any that might be required).
22. Open Arduino IDE. 
23. Open Boards manager. Go to Tools -> Board -> Boards Manager… (in our case it’s the DOIT ESP32 DEVKIT V1)
24. Select COM port that the board is attached to (if you don’t see the COM Port in your Arduino IDE, you need to install the ESP32 CP210x USB to UART Bridge VCP Drivers)
25. 
26. Modify sketch1 if you want to modify the number of seconds the LED is lit after detecting motion. Simply change the timeSeconds variable with the number of seconds you want.
27. Compile and upload the sketch1 to your ESP32 development board. If everything went as expected, you should see a “Done uploading” message. (You need to hold the ESP32 on-board Boot button while uploading).
28. Press the ESP32 on-board EN button to reboot it. 
    
29. Open the Serial Monitor at a baud rate of 115200.  
30. When motion detected (an interrupt is triggered), the ESP32 development board starts a timer and turns an LED on for 2 seconds. When the timer finishes counting down, the LED is automatically turned off.
31. 

Code

sketch. 

Let's check the blink sketch that works without a delay() function as it uses the millis() function instead.
The previous recorded time previousMillis substracted from the current time currentMillis. If the remainder is greater than the interval (in this case, 2000 milliseconds), the program updates the previousMillis variable to the current time, and either turns the LED on or off.
Because this snippet is non-blocking any code 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 to test it and modify the number of milliseconds in order to see how it works.

sketch1.

We assign two GPIO pins to the LED and PIR sensor. Then we create variables which will allow to set a timer to turn the LED off after motion detected.

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. In the setup() we sinitialise the serial communication at 115200 baud rate, 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 26 and it will call the function detectsMovement() on RISING mode. 

In every loop, the now variable is updated with the current time: now = millis(); When motion detected, the detectsMovement() function is called because we have 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. 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. The "Motion stopped" message will be printed in the Serial Monitor, the LED turned off, and the startTimer variable is set to false.

Summary

We have learnt how to use PIR sensor module with the ESP32 development board. 

Libraries

• No libraries required for this project

Sketch

• See attachments on the begining of this project