Circuit Documentation

Summary

This circuit integrates an ESP32 Devkit V1 microcontroller with an LCD TFT screen ILI9488 HD and interfaces with an OBD2 Diag module through UART communication. The ESP32 is responsible for controlling the display and processing data received from the OBD2 Diag module, which is connected to an OBD-II port for vehicle diagnostics. The circuit is designed to read vehicle speed from the OBD2 interface and display it on the LCD screen.

Component List

ESP32 Devkit V1

• Microcontroller with WiFi and Bluetooth capabilities.
• It has multiple GPIO pins for interfacing with peripherals and sensors.

LCD TFT screen ILI9488 HD

• A color display module with an ILI9488 controller.
• It supports SPI communication and has a backlight control pin.

OBD2 Diag

• A module for interfacing with a vehicle's On-Board Diagnostics (OBD) system.
• It provides access to various vehicle parameters and diagnostics data.

OBD-II port

• A standardized hardware interface in vehicles for self-diagnostics and reporting capability.

Wiring Details

ESP32 Devkit V1

• 3V3 connected to LCD TFT screen ILI9488 HD VCC (3.3~5V) for power.
• GND connected to LCD TFT screen ILI9488 HD GND and OBD2 Diag GND for common ground.
• D4 connected to LCD TFT screen ILI9488 HD RST for reset control.
• RX2 connected to LCD TFT screen ILI9488 HD D/C for data/command selection.
• D5 connected to LCD TFT screen ILI9488 HD CS for chip select.
• D18 connected to LCD TFT screen ILI9488 HD SCK for SPI clock.
• D19 connected to LCD TFT screen ILI9488 HD SDO(MISO) for SPI Master In Slave Out.
• D23 connected to LCD TFT screen ILI9488 HD SDI(MOSI) for SPI Master Out Slave In.
• RX0 connected to OBD2 Diag TX-O for UART receive.
• TX0 connected to OBD2 Diag RX-I for UART transmit.

LCD TFT screen ILI9488 HD

• BL connected to ESP32 Devkit V1 3V3 for backlight control.
• Other connections to ESP32 Devkit V1 as detailed above.

OBD2 Diag

• GND connected to ESP32 Devkit V1 GND for common ground.
• TX-O connected to ESP32 Devkit V1 RX0 for UART transmit.
• RX-I connected to ESP32 Devkit V1 TX0 for UART receive.

OBD-II port

• GND connected to OBD2 Diag GND for common ground.
• CANH connected to OBD2 Diag CAN HI for CAN high signal.
• CANL connected to OBD2 Diag CAN LO for CAN low signal.
• 12v connected to OBD2 Diag 12V+ for power supply.

Documented Code

#include <Wire.h>
#include <Adafruit_ILI9341.h>
#include <Adafruit_GFX.h>
#include <HardwareSerial.h>

#define TFT_CS     5
#define TFT_RST    4
#define TFT_DC     16
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_RST);

HardwareSerial mySerial(2); // UART2 (GPIO 16 RX, GPIO 17 TX)

void setup() {
  Serial.begin(115200);
  mySerial.begin(9600, SERIAL_8N1, 16, 17); // Setup UART2
  tft.begin();
  tft.setRotation(2); // Set display orientation
  tft.fillScreen(ILI9341_BLACK);
}

void loop() {
  mySerial.println("010D"); // Command to get speed from OBD2
  delay(1000);
  
  if (mySerial.available()) {
    String speedData = mySerial.readStringUntil('\r');
    int speed = parseSpeed(speedData);
    displaySpeed(speed);
  }
}

int parseSpeed(String data) {
  // Process data from OBD2
  if (data.length() > 6) {
    String speedHex = data.substring(6, 8);
    return strtol(speedHex.c_str(), NULL, 16);
  }
  return 0;
}

void displaySpeed(int speed) {
  tft.fillScreen(ILI9341_BLACK);

  // Set text size and color for speed
  tft.setTextSize(9); // Text size 9x standard size (corresponds to 90 pixels)
  tft.setTextColor(ILI9341_WHITE);

  // Calculate position for speed (center of display)
  int16_t x1, y1;
  uint16_t w, h;
  String speedStr = String(speed);
  tft.getTextBounds(speedStr, 0, 0, &x1, &y1, &w, &h);
  int speedX = (tft.width() - w) / 2;
  int speedY = (tft.height() - h) / 2 - 25; // Move slightly up

  // Display speed
  tft.setCursor(speedX, speedY);
  tft.print(speedStr);

  // Set text size and color for "km/h"
  tft.setTextSize(5); // Text size 5x standard size (corresponds to 50 pixels)
  tft.setTextColor(ILI9341_WHITE);

  // Calculate position for "km/h" (below speed)
  String unitStr = "km/h";
  tft.getTextBounds(unitStr, 0, 0, &x1, &y1, &w, &h);
  int unitX = (tft.width() - w) / 2;
  int unitY = speedY + h + 10; // Move below speed

  // Display "km/h"
  tft.setCursor(unitX, unitY);
  tft.print(unitStr);
}

This code initializes the ESP32 Devkit V1 and the LCD TFT screen ILI9488 HD, sets up UART communication with the OBD2 Diag module, and continuously reads and displays the vehicle speed on the LCD screen. The speed is requested from the OBD2 module, parsed from the response, and then displayed in a large font with the unit "km/h" below it.