Reverse-engineering the APsystems EZ1-M microinverter.
Replaces the factory ESP32-C2 firmware with ESPHome, giving you direct Home Assistant integration — no cloud, no app.
Disclaimer: Research and educational purposes only. Not affiliated with APsystems. Use at your own risk.
Sensors: DC voltage, current & power per channel, AC power, grid voltage & frequency, temperature, daily & lifetime energy, inverter state, DSP version.
Controls: Max power limit (30–800 W), inverter on/off.
The EZ1-M contains an ESP32-C2 (RISC-V, 26 MHz crystal) that talks to a TI C2000 DSP over UART at 57600 baud. The DSP does the actual inverting — the ESP32 is just the communication interface.
┌──────────────────────────────────────────────┐
│ APsystems EZ1-M Microinverter │
│ │
│ ┌──────────────┐ UART 57600 ┌───────────┐ │
│ │ ESP32-C2 │◄────────────►│ TI C2000 │ │
│ │ (WiFi/BLE) │ TX=GPIO2 │ DSP │ │
│ │ 26MHz XTAL │ RX=GPIO1 │ │ │
│ └──────────────┘ └───────────┘ │
└──────────────────────────────────────────────┘
The factory firmware supports BLE OTA — no need to open the inverter. First, compile the minimal ESPHome config to get a .bin file, then push it over BLE:
esphome compile esphome/ota.yaml
python3 scripts/ota.py .esphome/build/apsystems-ez1/.pioenvs/apsystems-ez1/firmware.bin -fThis is a one-way operation. ESPHome replaces the factory BLE stack, so you cannot OTA back to factory firmware. Reverting requires serial access to the ESP32-C2.
Once the minimal config is running and on WiFi:
esphome run esphome/full.yamlCopy esphome/full.yaml and adjust:
- Create a
secrets.yamlwithapi_key,ota_password,wifi_ssid,wifi_password,ap_password - Set "Lifetime Energy Offset" in Home Assistant to your known total kWh
- Tune divisors if your readings don't match your meter (see comments in config)
Upload firmware to an EZ1 running factory firmware over Bluetooth:
pip install bleak cryptography
python3 scripts/ota.py firmware.bin # normal update
python3 scripts/ota.py firmware.bin -f # force (skip version check)
python3 scripts/ota.py firmware.bin -v # verbose BLE debug# Check latest firmware version available
python3 scripts/vendor_fw/get_ota.py <DEVICE_ID>
# Download a firmware file by URL
python3 scripts/vendor_fw/dl_ota.py <URL>Frame format: FB FB <len> <data[len]> <chk_hi> <chk_lo> FE FE
Checksum = 16-bit sum of all bytes between header and checksum, big-endian.
| Offset | Conversion | Field |
|---|---|---|
| p[2:3] | major.minor | DSP firmware version |
| p[16:17] | ÷50 | CH1 DC voltage (V) |
| p[18:19] | ÷50 | CH2 DC voltage (V) |
| p[20:21] | ÷88 | CH1 DC current (A) |
| p[22:23] | ÷88 | CH2 DC current (A) |
| p[28:29] | seconds | Uptime since DSP boot |
| p[30:31] | raw | AC power (W) |
| p[32:33] | raw | Temperature (°C) |
| p[36:37] | ÷27.32 | Grid frequency (Hz) |
| p[38:39] | ÷10 | Grid voltage (V) |
| p[40:43] | ÷65536÷1000 | CH1 session energy (kWh) |
| p[44:47] | ÷65536÷1000 | CH2 session energy (kWh) |
| p[48] | 0x00/0x02/0x03 | State: Producing/Standby/Ramping |
| p[50:51] | inverse formula | Max power limit readback |
FB FB 06 AA E1 00 00 <raw_hi> <raw_lo> <chk_hi> <chk_lo> FE FE
Power encoding: raw = W²/1200 + 16.6034 × W + 300
ON = setMaxPower(800W), OFF = raw 0x0000.
Divisors are approximate (within ~5–10%). If your readings are off, compare against a known-good meter:
- DC voltage ÷50 — not independently verified
- DC current ÷88 — calibrated with clamp meter (3 data points)
- AC power — reads ~5–10% low vs meter
- Grid voltage ÷10 — close enough for monitoring
- Grid frequency ÷27.32 — should read ~50 Hz
esphome/
full.yaml Full ESPHome config (uses !secret references)
ota.yaml Minimal config for initial flash
scripts/
ota.py BLE OTA firmware uploader
vendor_fw/
get_ota.py Query APsystems cloud for firmware versions
dl_ota.py Download firmware files
MIT