Dr.ESP32

Download full project (contains programs for ESP32, programs for Raspberry Pi 4B and photos with video)

Table of Contents

• The motivation
• Description
• Typical Application
• Board of Materials
• Setup Procedure
  • ESP32
    • Hardware connections
    • Programming for ESP32
  • Raspberry Pi 4
    • Operating System installation
    • LAMP server installation
    • Programming for Raspberry Pi 4
• Arisen issues during development and solutions
• Gallery

The motivation

It was in 2020, a year that all people on Earth won't forget about the global pandemic. In Canada, beside other physical methods such as social distancing and sanitization, the only popular technological methods to slow the virus spread was COVID Alert App. COVID Alert App is a mobile app on both iOS and Android platforms. It can only work when the user enables Bluetooth on their smartphone. The smartphone will interact with nearby smartphone by exchanging encrypted bluetooth messages and store all the connection in the smartphone only. When an app user got infected by virus, he/she has to declare this to the app and the app will send alert from its database to other app users who have close contacted with that person.
Click here to learn more about the COVID Alert App.

However, there were many issues that this application cannot tackle:

• Privacy:

Many people were concerned about how their private information will be stored and used and who could access them.

• Dependency on users' device:

It could be that people left their phone at home when they go out, the WiFi connection is terrible to get alert in time, or simply they don't have a compatible smartphone

• Dependency on user's routine:

Smartphone users usually turn off the Bluetooth to increase battery life. Therefore, many app users may coincidentially leave the app running without Bluetooth which are useless and ineffective.

• Affordability:

Not everyone can afford a compatible smartphone, and not everyone can have regular WiFi access. This is the biggest challenge if the app is applied in remote areas and developing countries.

Therefore, this project arises to overcome all those challenges. Additionally, this is my first project with both ESP32 microcontroller and Raspberry Pi 4 single-board computer.

Description

The entire project consists of:

• One single Raspberry Pi 4 single-board computer as the database server, placed in a secure place with continuous power supply (cooling solutions such as heat sink, fan are recommended for long-term usage)
• Multiple Dr.ESP32 devices which contain a ESP32 microcontroller and a LiFePO4 3.2V 1200mAh battery as client device, attached to or come along with the user. Each device can run continuously for 14-15 hours under each full charge.

Typical Application

For example, this system is implemented in a supermarket. Each Dr.ESP32 is attached to the buggy or cart. The device should be disabled (under waiting state) in the buggy or cart station area. Whenever a new customer enters the supermarket and takes the buggy or cart out of the station, the Dr.ESP32 is activated (under working state). In this state,Dr.ESP32 continuously searches for any nearby Dr.ESP32 by scanning for any Bluetooth Low Energy (BLE) signal. The Dr.ESP32 will record that Dr.ESP32 in the contact list with the date and sent them to the database server (or store in EEPROM if it cannot connect to the server) if that Dr.ESP32 transmits a BLE signal that:

• is strong enough ( indicating that a nearby customer is standing closer than 2 meters from the original user )
• has correct BLE Address ( a list of BLE Address of each Dr.ESP32 is already stored in the sketch to identify if that is really from a Dr.ESP32 or from smartphone, headphones,... and which Dr.ESP32 it is )

When the customer checks out, the security guards will ask for his/her email and enter the device number to the database so the server can link the customer's email and the Dr.ESP32 device number together. In the future, this process will be automated by scanning customer member card (such as More Reward card, Air Miles card,..) and scan the NFT of the cart to get the Dr.ESP32 device number. In the future, if one of the past customers is infected, he/she can send the email to the supermarket with his/her virus test result for verification purposes. Once a staff reviews his/her email, they will enter the infected email into the database server. The server will automatically send an alert email to all people who had close contact with him/her.

Board of Materials

Below table is for a project with 1000 Dr.ESP32 devices. Change is neccessary accordingly to the number of Dr.ESP32 devices in the real application. Price is not including enclosure.

Device	Digi-Key Part Number	Number	Price
Raspberry Pi 4 Model B 4GB	1690-RASPBERRYPI4B/4GB-ND	1	87
ESP32-WROOM-32D(4MB)	1965-ESP32-WROOM-32D(4MB)CT-ND	1000	5601.40
1200mAh 3.2V LiFePO4 battery	-	1000	3250
Linear Voltage Regulator IC 1.5A	296-12602-1-ND	1000	362.50
BJT PNP 65V 6A 100mA 100Mhz 200mW SMD	BC856AW,135	1000	25.206
Shunt Voltage Reference IC 36V 1% SMD	TL431ACDBZT	1000	672.00
2.5 Ohm 1% 1/8W SMD 0805	CRCW08052R50FKTA	2000	45.2
470 Ohm 1% 0.1W SMD 0603	CR0603-FX-4700ELF	1000	3.91
110 Ohm 1% 0.1W SMD 0603	RC0603FR-07110RL	1000	5.59
1 kOhm 1%, 0.1W SMD 0603	ERJ-3EKF1001V	1000	8.59
2.49 kOhm 1% 0.1W SMD 0603	ERJ-3EKF2491V	1000	8.59

Total cost is 10069.986. An average of 10.07 for each device.
Unit of currency: CAD

Setup Procedure

ESP32

Hardware connections

Still under review but here is a sense of it. Update: Below circuit is ineffective anymore

Programming for ESP32

In this project, I use Arduino IDE for compiling and uploading the program. It is a free software and most tinkerer will be familiar with.

• First of all, if this is the first time you use ESP32 in Arduino IDE, you should install ESP32 Add-on for Arduino IDE
• Secondly, you may want to install the library PubSubClient.h library
• Thirdly the ESP32 can only store 1,310,720 bytes of sketch under default, which is not enough for our program (~ 1.5 KB). You should extend the sketch storage of the ESP32 by repartition the ESP32:

  • Change default.csv file

    • Open file C/Users/”YourName”/AppData/Local/Arduino15/packages/esp32/hardware/esp32/1.0.4/tools/partitions/default.csv
    • Change it into

    #Name	Type	SubType	Offset	Size	Flags
    nvs	data	nvs	0x9000	0x5000
    otadata	data	ota	0xe000	0x2000
    app0	app	ota_0	0x10000	0x340000
    eeprom	data	0x99	0x350000	0x1000
    spiffs	data	spiffs	0x351000	0xAF000

  • Change boards.txt file

    • Open file C/Users/”YourName”/AppData/Local/Arduino15/packages/esp32/hardware/esp32/1.0.4/boards.txt
    • Change the first block into

    esp32.name=ESP32 Max
    
    esp32.upload.tool=esptool_py
    esp32.upload.maximum_size=3407872
    esp32.upload.maximum_data_size=327680
    esp32.upload.wait_for_upload_port=true
    
    esp32.serial.disableDTR=true
    esp32.serial.disableRTS=true
    
    esp32.build.mcu=esp32
    esp32.build.core=esp32
    esp32.build.variant=esp32
    esp32.build.board=ESP32_DEV
    
    esp32.build.f_cpu=240000000L
    esp32.build.flash_size=4MB
    esp32.build.flash_freq=40m
    esp32.build.flash_mode=dio
    esp32.build.boot=dio
    esp32.build.partitions=default
    esp32.build.defines= 
    

• Now, you are ready to compile and upload the program code onto the ESP32 microcontroller. There are 3 files in total:
  • ESP32.ino
  • functions.cpp
  • functions.hpp
• Remember to modify the ssid and pass variables in the ESP32.ino file corresponding to your WiFi name and WiFi password.

Raspberry Pi 4

Operating System Installation

Follow this tutorial to install the OS. I recommend to install the Raspberry Pi OS (32-bit) Lite.

Notice: In step sudo nano /etc/dhcpcd.conf, use these lines instead:

interface wlan0
static ip_address = A/24
static routers = B
static domain_name_servers = B

where A is the Raspberry Pi IP Address (first 8-digit address from the command hostname -I) and B is A with last digit replaced by 1

LAMP Server Installation

Follow this tutorial to install the LAMP Server on Raspberry Pi 4.

Programming for Raspberry Pi 4

1. Preparing Your MySQL Database:
   • Open your browser and type http://A/phpmyadmin where A is the Raspberry Pi IP Address
   • Login by the account you setup before
   • Select the Databases menu at the top, complete the Create database fields by the drop down menu:
     • esp_data
     • utf8mb4_general_ci
   • Press the Create button
   • save your database name as esp_data
2. Create SQL tables:
   • Create SQL table to store contact between devices:
     • In the left sidebar select your database name esp_data
     • Open the SQL tab, Copy this SQL query into the SQL query field then press the Go button to create your table
   • Create SQL table to store customer information:
     • In the left sidebar select your database name esp_data
     • Open the SQL tab, Copy this SQL query into the SQL query field then press the Go button to create your table
   • Create SQL table to identify the infected customer :
     • In the left sidebar select your database name esp_data
     • Open the SQL tab, Copy this SQL query into the SQL query field then press the Go button to create your table
3. Create PHP files in Raspberry Pi 4:
   • PHP Script HTTP POST - Insert contact data into COVID 19 Database
     • Connecting to Raspberry Pi with an SSH connection, then type sudo nano /var/www/html/post-esp-data.php
     • Copy this PHP script to the newly created file
     • Remember to modify the $dbname, $username and $password variables with your own ones
   • PHP Script - Display COVID 19 Database Content
     • Type sudo nano /var/www/html/esp-data.php
     • Copy this PHP script to the newly created file
     • Remember to modify the $dbname, $username and $password variables with your own ones
   • PHP Script - Insert customer information into CustomerInfo Database
     • Type sudo nano /var/www/html/checkOutCustomer.php
     • Copy this PHP script to the newly created file
     • Remember to modify the $dbname, $username and $password variables with your own ones
   • PHP Script - Temporarily store infected customers from the original customer
     • Type sudo nano /var/www/html/trackInfection.php
     • Copy this PHP script to the newly created file
     • Remember to modify the $dbname, $username and $password variables with your own ones
4. Create Python file to send email upon request by LAMP Server
   • Connecting to Raspberry Pi with an SSH connection, then type sudo nano /var/www/html/newmailing.py
   • Copy this Python script to the newly created file
   • Remember to modify the username and password variables. This project will use a Gmail account to send out alert email.

Arisen issues during development and solutions

1. Too big sketch size
   • As mentioned in Programming for Raspberry Pi 4, the default available sketch size is 1,310,720 bytes meanwhile the program sketch size is ~1.5 KB so we have to change the partition setting of ESP32
2. Constantly rebooting when being powered by battery
   • There is a brownout sensor in ESP32 that makes the ESP32 reboot if it detects the supply voltage drops significantly. As our Dr.ESP32 is powered by battery, during setup, it has to draw huge current to initialize BLE and WiFi, leading to the significant supply voltage drop. Therefore, our Dr.ESP32 keeps rebooting and cannot work. To overcome this, we have to disable the brownout sensor during starting BLE and WiFi.
   • The solution is by adding these lines of code to disable brownout sensor at the beginning of setup and enable brownout sensor at the ending of setup.
     • WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0); to disable
     • WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 1); to enable
3. BLE connection is waiting for too long
   • I used to make the Dr.ESP32 exchange device number to recognize each other. However, there are some moments the BLE connection cannot connect and it just waits for really long time for the connection ( ~50 days in default) until it proceeds to the next instructions.
   • The solution is by changing the waiting time in the FreeRTO.cpp file:
     • Go to C/Users/”YourName”/AppData/Local/Arduino15/packages/esp32/hardware/esp32/1.0.4/libraries/BLE/src/FreeRTO.cpp
     • Change xSemaphoreTake(m_semaphore, portMAX_DELAY) into xSemaphoreTake(m_semaphore, 3000)

Gallery

Main hardware

Click on the image to play the demonstration video