growatt2radio

Point-to-point transmission of PV inverter data via 868 MHz radio signal to MQTT client with WiFi interface.

• Transmitter: Connection to PV inverter via Modbus interface (USB or RS-485)
• Radio transmission via 868 MHz ISM band; FSK modulation; max. range: ~150 m
• Revceiver: MQTT client with WiFi interface

growatt2lorawan-v2 worked totally fine for quite a while, but now my LoRaWAN node cannot communicate with any public gateway (The Things Network or Helium Network) any more from its present location. Presumably a new building and/or its scaffolding within line-of-sight between node and TTN gateway are blocking the radio signal path. This project is a workaround by using point-to-point transmission.

The implementation is based on a few existing projects.

Contents

• Hardware Requirements
  • Hardware Example (Transmitter)
• Inverter Modbus Interface Options
  • Modbus Interface Select Input
• Power Supply
• Pinning Configuration
  • Modbus Interface Selection
  • Modbus via RS485 Interface
  • Debug Interface in case of using Modbus via USB Interface (optional)
• Library Dependencies
• Software Build Configuration
• MQTT Integration
  • IoT MQTT Panel Example
  • Datacake Integration
  • Home Assistant Integration
• Legal

Hardware Requirements

• ESP32 (optionally with LiPo battery charger and battery)
• SX1276 or SX1262 (or compatible) LoRaWAN Radio Transceiver
• 868 MHz Antenna
• Transmitter
  • optional: RS485 Transceiver - 3.3V compatible, half-duplex capable (e.g Waveshare 4777 module)
  • optional: USB-to-TTL converter for Debugging (e.g. AZ Delivery HW-598)

Hardware Example (Transmitter)

• DFR0478 - FireBeetle ESP32 IoT Microcontroller
• TEL0125 - LoRa Radio 868MHz - FireBeetle Covers
• 868 MHz Antenna

Inverter Modbus Interface Options

1. USB Interface

   The inverter's USB port operates like a USB serial port (UART) interface at 115200 bits/s. If the length of a standard USB cable is sufficient to connect the ESP32 to the inverter (and there are no compatibility issues with the ESP32 board's USB serial interface), this is the easiest variant, because no extra hardware is needed.

   As pointed out in otti/Growatt_ShineWiFi-S, only CH340-based USB-Serial converters are compatible - converters with CP21XX and FTDI chips do not work!

2. COM Interface

   The inverter's COM port provides an RS485 interface at 9600 bits/s. An RS485 tranceiver is required to connect it to the ESP32.

Modbus Interface Select Input

The desired interface is selected by pulling the GPIO pin INTERFACE_SEL (defined in settings.h) to 3.3V or GND, respectively:

Level	Modbus Interface Selection
low (GND)	USB Interface
high (3.3V/open)	RS485 Interface

Power Supply

The ESP32 development board can be powered from the inverter's USB port which only provides power if the inverter is active.

No sun - no power - no transmission! 😎

But: Some ESP32 boards have an integrated LiPo battery charger. You could power the board from a battery while there is no PV power (at least for a few hours).

Pinning Configuration

See src/growatt_cfg.h

Modbus Interface Selection

GPIO define	Description
INTERFACE_SEL	Modbus Interface Selection (USB/RS485)

Modbus via RS485 Interface

GPIO define	Waveshare 4777 pin
MAX485_DE	RSE
MAX485_RE_NEG	n.c.
MAX485_RX	RO
MAX485_TX	DI

Debug Interface in case of using Modbus via USB Interface (optional)

USB-to-TTL converter, e.g. AZ Delivery HW-598

GPIO define	USB to TTL Converter
DEBUG_TX	RXD
DEBUG_RX	TXD / n.c.

Library Dependencies

• ModbusMaster by Doc Walker
• RadioLib by Jan Gromeš
• arduino-mqtt by Joël Gähwiler
• ArduinoJson by Benoît Blanchon
• Lora-Serialization by Joscha Feth

Software Build Configuration

• Install the Arduino ESP32 board package in the Arduino IDE
• Install all libraries listed in package.json — section dependencies — via the Arduino IDE Library Manager
• Clone (or download and unpack) the latest (growatt2radio release)
• Transmitter
  • Select your ESP32 board
  • Check / modify pin configuration in src/growatt_cfg.h
  • Build and upload examples/gw_transmitter/gw_transmitter.ino
• Receiver
  • Select your ESP32 board
  • Set your WiFi and MQTT credentials in examples/gw_receiver/secrets.h
  • Build and upload examples/gw_receiver/gw_receiver.ino

MQTT Integration

IoT MQTT Panel Example

Arduino App: IoT MQTT Panel

You can either edit the provided IoT MQTT Panel configuration file before importing it or import it as-is and make the required changes in IoT MQTT Panel. Don't forget to add the broker's certificate if using secure MQTT! (in the App: Connections -> Edit Connections: Certificate path.)

Editing scripts/iot_mqtt_panel_growatt2radio.json

Change CONNECTIONNAME, YOURMQTTBROKER, USERNAME and PASSWORD as needed:

[...]
"connectionName": "CONNECTIONNAME",
"host": "YOURMQTTBROKER",
[...]
"username":"USERNAME","password":"PASSWORD"
[...]

Datacake Integration

See Datacake MQTT Integration Documentation.

scripts/datacake_uplink_decoder.js is an example payload decoder. Change device_id and the MQTT topic variables as required.

With Datacake, you can get data reports as CSV files at regular intervals.

Home Assistant Integration

See scripts/home_assistant_configuration.yaml

Concept draft

Transmitter

• https://github.com/matthias-bs/growatt2lorawan-v2/blob/main/src/growattInterface.h
• https://github.com/matthias-bs/growatt2lorawan-v2/blob/main/src/growattInterface.cpp
• https://github.com/matthias-bs/growatt2lorawan-v2/blob/main/src/AppLayer.h
• https://github.com/matthias-bs/growatt2lorawan-v2/blob/main/src/AppLayer.cpp
• Arduino sketch
  • FSK transmitter configuration based on https://github.com/matthias-bs/SensorTransmitter/blob/main/SensorTransmitter.ino (uses RadioLib)
  • Operating sequence
    1. Power-on / wake-up
    2. Read data from PV inverter via Modbus interface
    3. Pack data into binary buffer
    4. Whitening / encryption?
    5. Add preamble, digest and transmitter ID
    6. Transmit packet via radio modem
    7. Sleep

Receiver

• https://github.com/matthias-bs/BresserWeatherSensorReceiver/tree/main/src
• https://github.com/matthias-bs/BresserWeatherSensorReceiver/blob/main/examples/BresserWeatherSensorMQTT/BresserWeatherSensorMQTT.ino
• Arduino sketch
  • FSK receiver configuration and based on BresserWeatherSensorReceiver (uses RadioLib)
  • Operating sequence
    1. Power-on / wake-up
    2. Wait for radio message preamble
    3. Receive message
    4. Validate digest and transmitter ID (optional)
    5. De-whitening / decryption?
    6. Convert binary payload buffer to JSON (reverse lora-serialization)
    7. Publish JSON data using MQTT via WiFi
    8. Sleep

Legal

This project is in no way affiliated with, authorized, maintained, sponsored or endorsed by Growatt or any of its affiliates or subsidiaries.