ESPHome configuration to monitor and control a ISolar/EASUN SMG II inverter via RS232

• ISolar SMG II
• EASUN SMG II
• SMG III 6.2kW 48V (mostly supported, some registers may not work)
• PowMr POW-HVM5.5K-48V / POW-HVM5.5K-48V-P
• Qoltec 53963 (supports SUF output priority)
• Anenji 3kW-24Vdc-120Vac (supports SUF output priority)
• Anenji 6200W-WiFi (charging priority "Utility first" probably not supported)

• ESPHome 2024.6.0 or higher.
• One half of an ethernet cable with RJ45 connector
• RS232-to-TTL module (MAX3232CSE f.e.)
• Generic ESP32 or ESP8266 board

               RS232                     UART-TTL
┌──────────┐              ┌──────────┐                ┌─────────┐
│          │              │          │<----- RX ----->│         │
│          │<---- TX ---->│  RS232   │<----- TX ----->│ ESP32/  │
│  SMG-II  │<---- RX ---->│  to TTL  │<----- GND ---->│ ESP8266 │
│          │<---- GND --->│  module  │<-- 3.3V VCC -->│         │<--- VCC
│          │              │          │                │         │<--- GND
└──────────┘              └──────────┘                └─────────┘

Please be aware of the different RJ45 pinout colors (T-568A vs. T-568B).

Some SMG II units (confirmed: 6KW/48V) expose RS232 via a USB-A COM port instead of the RJ45 jack. The USB data lines carry RS232 signals — VBUS and GND retain their standard meaning.

               RS232 via USB-A             UART-TTL
┌──────────┐                ┌──────────┐                ┌─────────┐
│          │  D+ ──── TX ──>│          │<----- RX ─────>│         │
│  SMG-II  │  D- ──── RX ──<│  MAX3232 │<----- TX ─────>│ ESP32   │
│  6KW     │  GND ─── GND ─>│  module  │<----- GND ────>│ S2 Mini │
│  USB-A   │  VBUS not used │          │<── 3.3V VCC ──>│         │
└──────────┘                └──────────┘                └─────────┘

A generic USB-A male DIP breakout board is the easiest way to access these pins without cutting a cable.

This firmware variant requires a proprietary wakeup frame before the first Modbus read. One transmission at boot is sufficient — the inverter stays awake as long as polls arrive within ≤10 s:

01 AA 06 DE A2

⚠️ This firmware uses different register addresses than the standard SMG II firmware documented in the Protocol section below. The addresses 201+ do not respond on these units. The following registers were confirmed by empirical scan:

Use esp32-s2-mini-usb-a-example.yaml as a starting point for this hardware variant.

Use the esp32-example.yaml / esp8266-example.yaml as proof of concept:

# Install esphome
pip3 install esphome

# Clone this project
git clone https://github.com/syssi/esphome-smg-ii.git
cd esphome-smg-ii

# Create a secret.yaml containing some setup specific secrets
cat > secrets.yaml <<EOF
wifi_ssid: MY_WIFI_SSID
wifi_password: MY_WIFI_PASSWORD

mqtt_host: MY_MQTT_HOST
mqtt_username: MY_MQTT_USERNAME
mqtt_password: MY_MQTT_PASSWORD
EOF

# Validate the configuration, create a binary, upload it, and start logs
# If you use a esp8266 run the esp8266-examle.yaml
esphome run esp32-example.yaml

The protocol is Modbus RTU via RS232.

None.

If this example doesn't work out of the box for your device please update your configuration to enable the debug output of the UART component and increase the log level to the see outgoing and incoming serial traffic:

logger:
  level: DEBUG
  # Don't write log messages to UART0 (GPIO1/GPIO3) if the inverter is connected to GPIO1/GPIO3
  baud_rate: 0

uart:
  id: uart_0
  baud_rate: 9600
  tx_pin: ${tx_pin}
  rx_pin: ${rx_pin}
  debug:
    direction: BOTH
    dummy_receiver: false

• https://powerforum.co.za/topic/11341-i-want-to-know-protocol-used-in-isolar-smg-ii-5kw/