Embedded Programming

This project aims to develop a prototype Point-of-Sale (POS) machine using an ESP32 microcontroller. The goal was to create an affordable POS device with a simple interface, like a keypad and LCD, to process transactions. This prototype forms the basis for integrating hardware into fintech ecosystems for secure transactions. It’s related to my fintech startup, Edris, in creating proprietary transaction devices to enhance product offerings.

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The Background

Point-of-Sale (POS) machines are essential for enabling transactions in retail and service environments. Traditionally, POS systems were bulky and expensive, accessible mainly to larger businesses. Advances in technology have made POS devices compact, affordable, and integrated with digital payment solutions, benefiting smaller businesses. IoT-enabled POS devices, like those using the ESP32 microcontroller, provide secure, customizable, and cost-effective solutions. In Egypt, the lack of POS machines limits small businesses from efficiently conducting cashless transactions, hindering financial inclusion and economic growth. By developing an affordable POS solution, I aim to address this gap and help drive economic growth.This project focuses on developing a prototype POS machine using an ESP32 microcontroller, with a simple interface like a keypad and LCD, aligning with the trend of accessible transaction technology. For my fintech startup, Edris, this project lays the foundation for creating proprietary transaction devices. By leveraging IoT technologies, we can expand beyond software to offer an integrated financial solution for small businesses and underserved markets, supporting our mission to democratize financial access.

I decided to make the embedded programming for a simple POS Machine.

The Works

Adding Components to the Wokwi Workspace

I added the following components to the workspace:

  1. 4x4 Keypad (to enter transaction amounts)

  2. 16x2 I2C LCD Display (to display information)

  3. LED (to indicate the transaction status)

Wiring the Components to the ESP32

1. Wiring the Keypad to the ESP32:

The 4x4 keypad has 8 pins (4 for rows, 4 for columns).

  • Connect the row pins (R1, R2, R3, R4) to GPIO13, GPIO12, GPIO14, and GPIO27 on the ESP32.

  • Connect the column pins (C1, C2, C3, C4) to: GPIO26, GPIO25, GPIO33, and GPIO32 on the ESP32.

2. Wiring the LCD to the ESP32:

The 16x2 LCD (I2C) has four pins: VCC, GND, SDA, and SCL.

  • Connect VCC to the 3.3V pin of the ESP32.

  • Connect GND to the GND pin of the ESP32.

  • Connect SDA to GPIO21 of the ESP32.

  • Connect SCL to GPIO22 of the ESP32.

3. Wiring the LED to the ESP32:

The LED has two pins: Anode (positive) and Cathode (negative).

  • Connect the anode to GPIO2 of the ESP32.

  • Connect the cathode to GND of the ESP32.

  • Add a 220Ω resistor in series between the cathode and GND.

Modifying the Code for the Components

This code snippet is part of the implementation for an ESP32-based Point-of-Sale (POS) machine. It includes the necessary libraries for handling Wi-Fi connectivity, keypad input, and LCD display, which are key components of the POS system. The setup() function initializes the serial communication, configures GPIO pins, sets up the LCD display, and connects to a Wi-Fi network using provided credentials. The loop() function continuously reads user input from a 4x4 keypad, which is used to enter transaction amounts. The LCD displays feedback for each key press, and upon submission (indicated by pressing #), the system processes the transaction by simulating it and turning on an LED as a status indicator. The connectToWiFi() function handles connecting the ESP32 to a Wi-Fi network, providing connectivity for future data transmission or remote interactions. This approach helps create a basic yet functional POS system that is easy to use and build.

The Final Product

Start the Simulation:

  • Click the green "Play" button in the Wokwi interface to start the simulation.

  1. Interact with the Components:

    • Use the keypad to enter numbers. You should see the input on the LCD display.

    • Press # to simulate submitting a transaction.

    • The LED should light up briefly, indicating the transaction is processing.

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