M5NtripClient

A portable NTRIP (Networked Transport of RTCM via Internet Protocol) client for M5Stack devices that receives RTK correction data from NTRIP casters and forwards it to u-blox GNSS receivers for high-precision positioning.

Overview

This project turns your M5Stack into a standalone NTRIP client that:

• Connects to WiFi networks
• Authenticates with NTRIP casters to receive RTCM correction data
• Forwards RTCM data to u-blox GNSS receivers via serial connection
• Sends GGA NMEA sentences back to the caster for accurate corrections
• Displays real-time status information on the M5Stack screen
• Provides a portable, battery-powered RTK solution

Features

• Auto-reconnection: Automatically reconnects to NTRIP server if connection is lost
• Real-time Display: Shows WiFi status, NTRIP connection, data rate, GPS quality
• GGA Feedback: Sends NMEA GGA sentences to caster every 5 seconds for optimal corrections
• Multi-tasking: Uses FreeRTOS tasks for concurrent operations
• Health Monitoring: Detects connection issues and automatically attempts recovery
• GPS Quality Indicators: Color-coded display showing fix quality (Invalid/GPS/DGPS/RTK Float/RTK Fixed)
• Button Controls: Power off and manual reconnection via physical buttons
• Data Statistics: Real-time RTCM data rate and total data received

Hardware Requirements

Bill of Materials (BOM)

• M5Stack Core 1 - ESP32-based development kit with display
• u-blox ZED-F9R - Multi-band GNSS receiver with RTK support
• Optional: Battery pack for M5Stack (for portable operation)

Wiring Diagram

Connect the M5Stack to the ZED-F9R as follows:

M5Stack Pin	ZED-F9R Pin	Description
5V	5V	Power supply
GND	GND	Ground
GPIO 16	TXO2	Serial receive (UART2 TX from GPS)
GPIO 17	RXD2	Serial transmit (UART2 RX to GPS)

Software Requirements

Dependencies

• PlatformIO - Development platform
• M5Unified - M5Stack unified library
• Arduino framework for ESP32

Compatible Platforms

• PlatformIO IDE
• Visual Studio Code with PlatformIO extension

Installation

1. Clone the Repository

git clone https://github.com/michalpelka/M5NtripClient.git
cd M5NtripClient

2. Configure Secrets

Create a secrets header file with your WiFi and NTRIP credentials:

cp include/Secrets/secrets.h.template include/Secrets/secrets.h

Edit include/Secrets/secrets.h with your actual credentials:

namespace secrets {
    const char* SSID = "your_wifi_ssid";              // Your WiFi network name
    const char* PASSWORD = "your_wifi_password";      // Your WiFi password
    const char* NTRIP_HOST = "ntrip.example.com";     // NTRIP caster hostname
    const uint16_t NTRIP_PORT = 2101;                 // NTRIP caster port (typically 2101)
    const char* NTRIP_MOUNTPOINT = "MOUNTPOINT";      // Your NTRIP mountpoint
    const char* NTRIP_USERNAME = "username";          // NTRIP username
    const char* NTRIP_PASSWORD = "password";          // NTRIP password
}

3. Configure u-blox Receiver

You need to configure your u-blox ZED-F9R receiver using u-center software:

Required Settings:

• Accept RTCM corrections on UART2 (RXD2)
• Output only GGA NMEA sentences on UART2 (TXD2)
• Set UART2 baudrate to 115200

A pre-configured settings file is provided: p9r+m5stack.ucf

To apply settings in u-center:

1. Connect ZED-F9R to your computer via USB
2. Open u-center software
3. Load the configuration file: Tools > Receiver Configuration > Load Configuration → select p9r+m5stack.ucf
4. Transfer to receiver: Tools > Receiver Configuration > Transfer file > GPS
5. Save to BBR/Flash: View > Configuration View > CFG > Save current configuration

4. Build and Upload

Using PlatformIO CLI:

pio run --target upload

Or use the PlatformIO IDE interface to build and upload.

Usage

Starting the Device

1. Power on your M5Stack
2. The device will:
   • Connect to WiFi (displays connection status)
   • Connect to NTRIP caster
   • Authenticate with the caster
   • Begin receiving and forwarding RTCM data

Display Information

The M5Stack display shows:

• IP Address: Current WiFi IP
• WiFi RSSI: Signal strength in dBm
• RTCM Data Rate: Current data rate in bytes/second
• Total Data: Cumulative data received in KB
• NTRIP Status: Connected (green) or disconnected (red) with retry count
• GGA Quality: GPS fix quality with color coding:
  • 🔴 Red (0): Invalid/No fix
  • 🟡 Yellow (1): GPS fix
  • 🔵 Cyan (2): DGPS fix
  • 🟢 Green (5): RTK Float
  • 🟢 Green-Yellow (4): RTK Fixed
• GGA Sentence: Current NMEA GGA sentence from receiver

Power off

Double click red button on the side of M5Stack.

Serial Monitor

Connect to serial monitor at 115200 baud to see debug information:

pio device monitor

Troubleshooting

Cannot Connect to WiFi

• Verify SSID and password in secrets.h
• Check WiFi signal strength
• Ensure 2.4GHz WiFi network (ESP32 doesn't support 5GHz)

Cannot Connect to NTRIP Server

• Verify NTRIP host, port, and credentials in secrets.h
• Check that mountpoint exists and is accessible
• Verify internet connectivity
• Some NTRIP services require valid subscription

No RTK Fix

• Ensure ZED-F9R has clear view of sky
• Verify RTCM data is being received (check data rate on display)
• Confirm GGA sentences are being sent to caster
• Check that mountpoint provides corrections for your location
• RTK requires time to converge (typically 30 seconds to several minutes)

No Data Displayed

• Verify wiring between M5Stack and ZED-F9R
• Check baudrate configuration (115200)
• Ensure ZED-F9R is configured to output GGA on UART2

Device Restarts/Crashes

• Check power supply (USB or battery)
• Monitor serial output for error messages
• Verify all connections are secure

Development

Project Structure

M5NtripClient/
├── src/
│   ├── main.cpp        # Main application logic
│   ├── ntrip.cpp       # NTRIP client implementation
│   └── base64.cpp      # Base64 encoding for authentication
├── include/
│   ├── ntrip.h         # NTRIP client header
│   ├── base64.h        # Base64 encoding header
│   └── Secrets/
│       └── secrets.h.template  # Template for credentials
├── platformio.ini      # PlatformIO configuration
└── p9r+m5stack.ucf     # u-blox receiver configuration

Key Components

• FreeRTOS Tasks:
  • lcdUpdateTask: Updates display every second
  • ggaReadTask: Reads GGA sentences from GPS
  • healthCheckTask: Monitors connection health
• Main Loop: Handles NTRIP data reception and GGA transmission

Contributing

Contributions are welcome! Please feel free to submit issues or pull requests.

License

This project is licensed under the GNU General Public License v2.0 - see the LICENSE file for details.

Acknowledgments

• Built with M5Unified library
• Uses PlatformIO development platform
• Implements NTRIP protocol for RTK corrections (custom implementation following NTRIP v1.0 specification)
• Utilizes Base64.c library

Author

Michał Pełka - michalpelka