growatt-esp8266
A library to monitor a Growatt MTL-5000 using an ESP8266 (Wemos D1) via a modbus over RS232 interface.
Software
The library uses a software serial port to connect to the inverter to retrieve data using its Modbus interface. Modbus provides a set of predefined parameters available at certain addresses, which can be queried using a "read register" commmand. This library will:
- Create a software serial port on the pins you specify
- Create a modbus master using this serial port
- Read data from the modbus client (the inverter) registers, decode it and make it available via the library
Using the library
#include <GrowattInverter.h>
#define PIN_TX D5
#define PIN_RX D6
#define SLAVE_ADDRESS 1
GrowattInverter inverter(PIN_RX, PIN_TX, SLAVE_ADDRESS);
void setup(){
Serial.begin(9600);
}
void loop(){
inverter.read();
if(inverter.valid){
// Power output from the PV panels
Serial.println(inverter.Ppv);
// Power output from the inverter
Serial.println(inverter.Pac1);
}else{
Serial.println("Inverter read failed");
}
delay(1000);
}
Hardware
See the hardware/ directory for EAGLE schematic and circuit board design.
To simplify board design and fabrication, the board uses a module for the esp8266 and all through hole components beyond this.
The board itself is comprised of:
- Wemos D1 Mini
- LM7805 voltage regulator
- 1x330uF capacitor (for main power)
- MAX232 level converter
- 3x 1uF capacitors (for MAX232)
- 3x 3mm leds + 1/4W resistors (optional)
Pinout
The growatt inverter I have has a DB9 connector for an RS232 connection, which has the pinout:
FROM INVERTER
----------------------- 2 = TX
\ (5) (4) (3) (2) (1) / 3 = RX
\ (9) (8) (7) (6) / 5 = GND
\_________________/ 9 = V+ (about 8 volts)
Inverter DB9 Our DB9 PCB Wemos
(female) (male) (J4) (pins)
2 ---(TX)----(RX)--- 2 --------- 3 ---(RX)--- D6
3 ---(RX)----(TX)--- 3 --------- 4 ---(TX)--- D5
5 ---(GND)---------- 5 --------- 1 ---------- GND
9 ---(V+)----------- 9 --------- 2 -- VREG -- VCC
Sample project
I've included a complete sample project using the board and software library if you just want to get this running on your own inverter. It uses an MQTT + WiFi wrapper library I put together a while ago called iot-thing but you should be easily able to rip this out and use your own code for the internet / wifi connectivity side of things.
Enclosure
Coming soon...
Todo
- Example project should use self configuring captive portal for wifi setup
- Add a simple web UI to show present values from the inverter
- WiFi Serial debugging using socket