GPS Speedometer, a ESP32 project

This GPS speedometer reads real-time velocity data from a NEO-6M GPS module and displays it on a TFT screen. The ESP32 processes satellite signals to calculate speed and tracks the maximum velocity reached during operation.

The guide includes a complete wiring diagram showing how to connect the GPS module's power and serial data lines to the ESP32, a full parts list, and ready-to-upload firmware that handles GPS parsing, display rendering, and speed calculations. Assembly takes just a few minutes, and once powered up, the device will acquire a satellite lock and begin showing live speed readings.

Wiring diagram

Gather all the parts

Qty	Component
1	NEO-6M GPS Module NEO-6M u-blox NEO-6M based GPS receiver module. Outputs NMEA sentences (GGA, RMC, etc.) over UART at 9600 baud by default. Provides latitude, longitude, altitude, speed, and time. The NEO-6M module itself is a 3.3V-class device; many GY-NEO6MV2 breakout boards accept 5V on their VCC header through an onboard regulator, but UART I/O remains 3.3V-domain and must not be driven above 3.6V. Features an on-board patch antenna footprint and an SMA/IPEX connector for external active antenna (preferred for faster lock acquisition). Supply current ~45 mA in acquisition, ~11 mA in tracking.

Qty

Component

NEO-6M GPS Module

NEO-6M

u-blox NEO-6M based GPS receiver module. Outputs NMEA sentences (GGA, RMC, etc.) over UART at 9600 baud by default. Provides latitude, longitude, altitude, speed, and time. The NEO-6M module itself is a 3.3V-class device; many GY-NEO6MV2 breakout boards accept 5V on their VCC header through an onboard regulator, but UART I/O remains 3.3V-domain and must not be driven above 3.6V. Features an on-board patch antenna footprint and an SMA/IPEX connector for external active antenna (preferred for faster lock acquisition). Supply current ~45 mA in acquisition, ~11 mA in tracking.

Assemble it in 4 steps

1. Place the GPS receiver

Put the NEO-6M GPS module where its small square antenna faces upward and is not covered by metal. For the first test, place it near a window or outdoors so it can see the sky.

The first satellite lock can take several minutes, especially after the module has been stored without power.
Do not put the antenna directly under the ESP32 board or a metal case; blocked sky view prevents a speed reading.

2. Connect GPS power

With the ESP32 unplugged, connect the GPS VCC pin to the board 3V3 pin (power). Connect GPS GND to a board GND pin (ground).

Use short jumper wires and make sure the labels on the GPS module match the labels you connect.
Do not connect GPS VCC to 5V unless your exact GPS breakout is clearly marked as accepting 5V; the design uses the safe 3.3V connection. Swapped VCC and GND can damage the GPS module.

3. Connect the two data wires

Connect GPS TX to ESP32 GPIO3 / RX0 (data). Connect GPS RX to ESP32 GPIO1 / TX0 (data). Leave the GPS PPS pin unconnected.

TX and RX cross over: the GPS pin marked TX goes to the board pin marked RX0, and GPS RX goes to TX0.
Keep these two wires clear of VCC and GND. A loose TX wire will leave the display showing SEARCHING.

4. Power up and get a satellite lock

Check every connection once more, then plug the ESP32 board into USB. Put the antenna where it can see open sky; the screen changes from SEARCHING to LOCKED when the GPS receiver has enough satellites.

Walk or ride slowly in an open area after it says LOCKED; the large number should then show your speed in km/h.
Do not use the displayed speed as a safety-critical instrument while driving; use the vehicle's approved speedometer and obey local laws.

Review all connections

1. Connections between "gps_neo6m" and "ESP32"

Function	gps_neo6m	ESP32
`power`	VCC	3V3
`ground`	GND	GND
`uart`	TX	GPIO 3
`uart`	RX	GPIO 1

Deploy the firmware

main.cppOpen in Schematik

#include <Arduino.h>
#include <TinyGPS++.h>
#include <Arduino_GFX_Library.h>


// Forward declarations
void drawStaticScreen();
void drawSpeed(float speed);
void drawStatus(bool fixed);
void drawTopSpeed();

constexpr int GPS_RX_PIN = 3;  // GPS TX connects here
constexpr int GPS_TX_PIN = 1;  // GPS RX connects here
constexpr uint32_t GPS_BAUD = 9600;

HardwareSerial gpsSerial(2);
TinyGPSPlus gps;

Arduino_ESP32SPI tftBus(2, 15, 14, 13, GFX_NOT_DEFINED);
Arduino_ILI9341 display(&tftBus, GFX_NOT_DEFINED, 0, false, 240, 320);

float shownSpeed = -1.0f;
float topSpeed = 0.0f;
bool shownFix = false;
uint32_t lastDataMs = 0;

void drawStaticScreen() {
  display.fillScreen(BLACK);
  display.setTextColor(CYAN);
  display.setTextSize(2);
  display.setCursor(44, 22);
  display.print("SPEEDOMETER");

  display.drawRoundRect(12, 58, 216, 142, 12, DARKCYAN);
  display.setTextColor(WHITE);
  display.setTextSize(2);
  display.setCursor(91, 168);
  display.print("km/h");

  display.drawFastHLine(20, 205, 200, DARKGREY);
  display.setTextColor(LIGHTGREY);
  display.setTextSize(2);
  display.setCursor(24, 220);
  display.print("TOP:");
  display.setCursor(24, 250);
  display.print("GPS:");

}

void drawSpeed(float speed) {
  display.fillRoundRect(18, 64, 204, 130, 8, BLACK);
  display.setTextColor(speed < 1.0f ? ORANGE : GREEN);
  display.setTextSize(7);
  char speedText[10];
  snprintf(speedText, sizeof(speedText), "%3.0f", speed);
  int16_t x1, y1;
  uint16_t w, h;
  display.getTextBounds(speedText, 0, 0, &x1, &y1, &w, &h);
  display.setCursor((240 - w) / 2, 104);
  display.print(speedText);
}

void drawStatus(bool fixed) {
  display.fillRect(82, 246, 140, 20, BLACK);
  display.setTextSize(2);
  display.setTextColor(fixed ? GREEN : RED);
  display.setCursor(82, 250);
  display.print(fixed ? "LOCKED" : "SEARCHING");
}

void drawTopSpeed() {
  display.fillRect(82, 216, 130, 22, BLACK);
  display.setTextColor(YELLOW);
  display.setTextSize(2);
  display.setCursor(82, 220);
  display.printf("%.1f km/h", topSpeed);
}

void setup() {
  display.begin();
  display.setRotation(0);
  drawStaticScreen();
  drawSpeed(0.0f);
  drawTopSpeed();
  drawStatus(false);
  gpsSerial.begin(GPS_BAUD, SERIAL_8N1, GPS_RX_PIN, GPS_TX_PIN);
}

void loop() {
  while (gpsSerial.available() > 0) {
    gps.encode(gpsSerial.read());
  }

  const bool hasRecentFix = gps.location.isValid() && gps.location.age() < 3000;
  if (hasRecentFix != shownFix) {
    shownFix = hasRecentFix;
    drawStatus(shownFix);
  }

  if (gps.speed.isUpdated()) {
    lastDataMs = millis();
    float speedKmh = gps.speed.kmph();
    if (speedKmh < 0.5f) speedKmh = 0.0f;
    if (speedKmh > topSpeed) {
      topSpeed = speedKmh;
      drawTopSpeed();
    }
    if (fabs(speedKmh - shownSpeed) >= 0.5f) {
      shownSpeed = speedKmh;
      drawSpeed(speedKmh);
    }
  }

  if (millis() - lastDataMs > 3500 && shownSpeed != 0.0f) {
    shownSpeed = 0.0f;
    drawSpeed(0.0f);
  }

  delay(5);
}