Networking and Communications

Introduction

This week focused on establishing communication between multiple microcontroller systems. The goal was to create a functional network where one board transmits data and another receives and processes it for display.

In my implementation, I built a two-node wired communication system using two ESP32 microcontrollers. One node functions as a sender (input node) interfaced with an RFID reader, while the second node acts as a receiver (output node) equipped with an I2C LCD display.

The core communication protocol used was UART (Universal Asynchronous Receiver-Transmitter / Serial Communication), where data packets are transferred between boards using cross-connected TX/RX lines and a common ground reference.

Objectives

Group Assignment

• Send a message between two projects or microcontroller boards.
• Understand communication protocols, timing requirements, and signal transmission integrity.

→ View Group Assignment Documentation

Individual Assignment

• Design and connect multiple nodes with unique network addressing schemes.
• Implement communication pipelines between dedicated input and output devices.
• Document the complete development workflow, hardware challenges, and final operational results.

Tools & Technologies

Hardware Components

• ESP32 Microcontrollers (x2): Dual-core nodes executing sender and receiver tasks.
• MFRC522 RFID Reader: 13.56 MHz RFID module used to read unique IDs from cards/tags.
• RFID Card/Tag: High-frequency transponder storing fixed identification payload data.
• 16x2 I2C LCD Display: Visual display module for rendering incoming packet data.
• Jumper Wires: Interconnect cables for crossed TX/RX UART transmission and power lines.

Software & Drivers

• Arduino IDE: Development interface for writing C++ code and monitoring serial buses.
• CP210x USB-to-UART Bridge VCP Driver: Essential host driver for ESP32 board detection.

Software Libraries

• SPI.h – Hardware SPI library for interfacing with the MFRC522 reader.
• MFRC522.h – Driver library for MFRC522 RFID card detection and UID parsing.
• Wire.h – Two-Wire I2C bus interface library.
• LiquidCrystal_I2C.h – Serial I2C character LCD controller library.

Workflow & Implementation

Step 1: Debugging ESP32 Connection & Driver Setup

Initially, I encountered a critical issue where the ESP32 board was not detected by my operating system, preventing uploading from the Arduino IDE.

Upon inspecting Windows Device Manager, I noticed a driver warning indicator showing that the computer lacked the required CP210x USB-to-UART Bridge Driver.

Troubleshooting Steps & Resolution:

1. Downloaded the Silicon Labs CP210x VCP drivers from the Silicon Labs Driver Download Page.
2. Extracted and executed the driver setup installer on the host workstation.
3. Rebooted the workstation and reconnected the ESP32 via USB.

After installation, the Virtual COM Port (COM) appeared correctly in Arduino IDE:

Step 2: System Architecture (Two-Node Network)

I structured a master-slave styled serial communications system consisting of two independent processing nodes:

• Node 1 (Sender): ESP32 reading card UIDs via SPI from an MFRC522 RFID reader.
• Node 2 (Receiver): ESP32 listening on its RX line and printing payloads to an I2C LCD screen.

Step 3: ESP32 Pinout Mapping & Independent Node Verification

I consulted the standard ESP32 pinout reference to identify dedicated SPI, I2C, and UART pins prior to hardware assembly.

Testing Node 1: RFID MFRC522 Reader

The MFRC522 module uses the high-speed SPI (Serial Peripheral Interface) protocol. I connected SCK, MISO, MOSI, SDA, and RST to default ESP32 SPI pins and uploaded a test sketch to confirm UID parsing.

RFID Standalone Demonstration Video

Testing Node 2: 16x2 I2C LCD Display

I independently verified Node 2 using an I2C scanner and a simple LCD initialization sketch to confirm contrast and character display.

Step 4: Establishing Hardware UART Interconnection

UART transmission requires crossing data signals between nodes while bonding ground potential:

• Sender TX (Transmit Pin) → Receiver RX (Receive Pin)
• Sender GND → Receiver GND (Common Ground Reference)

Note: Crossing TX to RX is fundamental so that outgoing bit toggles align directly with the remote node's input shift register.

Step 5: Node 1 Payload Transmission Code

When an RFID card is swiped, Node 1 parses the hexadecimal byte array into a string payload and streams it down the serial line:

// Transmit parsed UID string over UART Serial
Serial.println(uid);

Step 6: Node 2 Reception & LCD Rendering Code

Node 2 checks its hardware serial buffer for incoming newline-terminated byte streams and outputs them onto the LCD screen:

if (Serial.available()) {
  String msg = Serial.readStringUntil('\n');

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Received:");

  lcd.setCursor(0, 1);
  lcd.print(msg);
}

Step 7: Network Addressing & Message Formatting

To simulate multi-node networking over shared lines, I added sender identification headers (node addressing) to the transmitted payload:

// Formatting payload with Node Source ID
Serial.println("NODE1:" + uid);

This prefix allows receiver nodes to filter and distinguish payload origins in multi-device bus networks.

Results & Validation

• Established stable inter-board UART communication between two separate ESP32 systems.
• Real-time SPI read of RFID UIDs transmitted cleanly over serial line to receiving node.
• Instantaneous rendering of received packet payload on I2C LCD screen.

Data Pipeline Flow:

[Scan RFID Tag] ──SPI──> [Node 1: ESP32] ──UART TX/RX──> [Node 2: ESP32] ──I2C──> [16x2 LCD Display]

Complete Network System Demonstration Video

Challenges & Solutions

1. ESP32 Host Connection Failure

Cause: Absence of CP210x USB-to-UART bridge controller drivers on host PC.
Solution: Installed official Silicon Labs VCP drivers and verified active COM assignment in Device Manager.

2. Data Transmission Not Registering on Receiver

Cause: Direct parallel wiring (TX to TX) instead of cross wiring.
Solution: Swapped wire placement so Node 1 TX connected directly to Node 2 RX with common GND.

3. Garbage Characters or Garbled Serial Text

Cause: Baud rate mismatch between sender and receiver serial initialization.
Solution: Standardized both firmware sketches to run at matching 115200 baud rates.

4. LCD Library Compilation Errors

Cause: Conflicting header functions across generic LiquidCrystal repositories.
Solution: Used the standard LiquidCrystal_I2C library compatible with PCF8574 backpacks.

What I Learned

• Fundmentals of UART Serial Communication (TX/RX timing, baud rate sync, common ground requirements).
• Simultaneous management of multiple protocol buses (SPI for RFID, UART for inter-board networking, I2C for display).
• Importance of host VCP drivers in physical hardware debugging environments.
• Implementing sender node address headers to form structured network payloads.
• Systematic unit-testing procedures: validating sensor/actuator nodes individually prior to network integration.

Downloads & Links