Growatt Modbus TCP Gateway

ESP8266 firmware that converts Modbus RTU (from Growatt inverter) to Modbus TCP for home automation integration.

Overview

This firmware turns a ShineWiFi-X stick into a Modbus TCP gateway, enabling home automation systems like Homey, Home Assistant, or OpenHAB to read real-time data from Growatt solar inverters.

Key Features:

• 🔌 Modbus RTU Master (reads from Growatt inverter via USB/Serial)
• 🌐 Modbus TCP Server (serves data over WiFi network)
• ⚡ Low latency - optimized for ESP8266 performance
• 📊 Protocol 1.20 support (TL-X series inverters)
• 🔧 Serial setup menu (button + USB terminal for WiFi and Modbus settings)

Hardware Requirements

• ShineWiFi-X stick (ESP8266 ESP-07S based)
  • 1MB flash, 80MHz CPU
  • USB-to-Serial (CH340) interface
• Growatt Inverter with Modbus support
  • Tested with: 600TL-X (115200 baud, protocol v1.20)
  • Should work with: TL-X, TL3-X, MIC series

Supported Data Points

The gateway reads and publishes the following registers via Modbus TCP:

Real-time Data (Registers 0-48)

• Inverter status
• DC input power, voltage, current (PV1, PV2)
• AC output power (total + per phase)
• Grid voltage, current, frequency
• Temperature

Energy Counters (Registers 53-60)

• Energy produced today (kWh)
• Total energy produced (kWh)

Installation

Prerequisites

• PlatformIO (IDE or CLI)
• USB cable for flashing

Build & Upload

1. Clone the repository

   git clone https://github.com/jochemkroon/GrowattModbusTCP.git
   cd GrowattModbusTCP

2. Configure WiFi credentials

   WiFi and Modbus settings are configured via the serial setup menu (no code edit required).

3. Build and upload

   # Using PlatformIO CLI
   pio run -e ModbusTCP-Gateway --target upload
   
   # Or use VSCode PlatformIO extension
   # Click "Upload" in the PlatformIO toolbar

4. Connect to inverter

   • Disconnect ShineWiFi-X from computer
   • Plug into Growatt inverter USB port
   • The stick will connect to WiFi and start serving Modbus TCP

WiFi Setup (Button + Serial Menu)

Use this flow to configure WiFi and network settings:

1. Connect the ShineWiFi-X stick to USB.
2. Open a serial monitor at 115200 baud.
3. Reset/power-cycle the stick.
4. During boot, when you see Checking button..., hold the hardware button for 5 seconds.
5. Wait for CONFIG MODE ACTIVATED! and the menu.
6. Use menu options:
   • 1 set WiFi SSID
   • 2 set WiFi password
   • 3 toggle static IP on/off
   • 4, 5, 6 set IP, gateway, subnet
   • 7, 8, 9 set Modbus ID, baud, TCP port
   • S save and restart
   • R restore defaults and restart
   • X exit without saving

After restart, the gateway boots with the saved settings.

Configuration

Modbus RTU Settings

Default configuration in code:

#define DEFAULT_MODBUS_RTU_SLAVE_ID    1
#define DEFAULT_MODBUS_RTU_BAUD        115200

Modbus TCP Settings

#define DEFAULT_MODBUS_TCP_PORT        502

Update Interval

#define READ_INTERVAL 30  // seconds

Usage

Connecting from Homey

1. Install "SolarEdge + Growatt TCP modbus" app
2. Add device with these settings:
   • IP Address: 192.168.1.100 (your static IP)
   • Port: 502
   • Modbus ID: 1
   • Poll Interval: 30-60 seconds

Key Register Addresses (Protocol 1.20)

Register	Data Point	Type	Multiplier	Unit
0	Inverter Status	16-bit	1	-
1-2	DC Power Total	32-bit	0.1	W
3	PV1 Voltage	16-bit	0.1	V
5-6	PV1 Power	32-bit	0.1	W
35-36	AC Power Total	32-bit	0.1	W
37	Grid Frequency	16-bit	0.01	Hz
38	AC Voltage L1	16-bit	0.1	V
40-41	AC Power L1	32-bit	0.1	W
53-54	Energy Today	32-bit	0.1	kWh
55-56	Energy Total	32-bit	0.1	kWh

LED Indicators

• Green (GPIO0): Inverter communication OK
• Red (GPIO2): Communication error
• Blue (GPIO16): WiFi activity

Technical Details

Memory Usage

• RAM: ~30KB (36.8% of 80KB)
• Flash: ~320KB (33.4% of 958KB)

Network

• Static IP recommended for reliability
• Modbus TCP uses standard port 502
• WiFi reconnect on connection loss

Protocol

Based on Growatt Modbus Protocol v1.20 for TL-X series inverters.

Troubleshooting

No WiFi connection

• Enter setup mode via button + serial menu and verify SSID/password
• If static IP is enabled, verify IP/gateway/subnet values
• Use R in the serial menu to restore defaults and reconfigure

No data from inverter

• Verify inverter Modbus settings (slave ID, baud rate)
• Check USB connection (try different cable)
• Monitor serial output during boot

Homey shows 0W

• Verify Homey is configured for register 35-36 (AC Power)
• Check if inverter is actively producing (daylight, grid connected)
• Test with manual Modbus TCP client tool

Development

Project Structure

Growatt_ShineWiFi-X-master/
├── SRC/
│   └── GrowattModbusTCP.ino    # Main firmware
├── platformio.ini               # PlatformIO config
└── README.md

Libraries Used

• ModbusMaster v2.0.1 - Modbus RTU client
• modbus-esp8266 v4.1.0 - Modbus TCP server

License

MIT License.

Credits

• Based on Growatt_ShineWiFi-X hardware documentation
• Growatt Modbus protocol definitions (v1.20, v1.24, v3.05)

Support

For issues specific to this Modbus TCP gateway, please open an issue on GitHub.

For general Growatt inverter questions, consult the official Growatt documentation.