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Shelly Plug PM Gen3

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State: partly checked Generation: 3 Chip: ESP32-C3 Relay: none

🧰 Before you start · ⚙️ Config · 📍 Pins · ⚡ Flash it · 👀 What to expect · ↩️ Way back

This plug only measures: Shelly lists the Plug PM Gen3 as a monitoring device, and there is no relay in it. Do not confuse it with the Plug M Gen3, which switches.

Fact Value
Profile PlugPMG3
Model S3PL-30116EU
Flash 8 MB
Official package 2.1.0 (stable since 2026-10-14; Bootloader, partition table and filesystem are the same as in 2.0.1; the hardware run was made with 2.0.1)
Partition table 0x10000
App slot size 0x280000 (smaller than the Plug M and Plug S, 0x2a0000)

Note

Partly checked: flashed over OTA with this tool on a real plug (send with --esphome-factory; reported by the owner, 2026-10-12). The log lines and the readings are not recorded here yet.

Before you start

Check first:

  • the device runs Shelly's own firmware, not ESPHome yet
  • you know its IP address (--ip), or this PC is on the device's own access point (default 192.168.33.1)
  • the device can reach this PC: same network, port 8000 (--port) not blocked
  • your ESPHome config uses the partition table below and is compiled
  • a UART adapter is at hand as your way back (Recovery over UART)

Also:

  • The device is a Plug PM Gen3 (PlugPMG3, S3PL-30116EU), not a Plug M.

ESPHome config

Important

build refuses a config without Shelly's partition table. Copy partitions/PlugPMG3-stock.csv from this repository next to your YAML and keep CONFIG_PARTITION_TABLE_OFFSET: "0x10000".

esp32:
  variant: ESP32C3
  board: esp32-c3-devkitm-1
  flash_size: 8MB
  partitions: PlugPMG3-stock.csv        # copy from partitions/ in this repository
  framework:
    type: esp-idf
    sdkconfig_options:
      CONFIG_PARTITION_TABLE_OFFSET: "0x10000"
    advanced:
      enable_ota_rollback: false

ota:
  - platform: esphome
    allow_partition_access: true

Use this device's own PlugPMG3-stock.csv. The Plug M and Plug S tables have bigger app slots and different file system offsets, and build --esphome-yaml refuses a config whose slot size does not match the profile.

Pins

Read from the stock 2.0.1 firmware (a flash dump and the boot log of a real plug). Not verified against the plug: nobody has reported readings from a running ESPHome on it yet.

Function Pin
BL0942 power meter (UART1, 9600 8N1) ESP RX GPIO6, ESP TX GPIO7
Button (polarity assumed: pull-up, inverted) GPIO18
LED: addressable, 4 pixels (RMT, 20 MHz); chip type and colour order are copied from the Plug S, not read GPIO5
BL0942 CF/ZX pin (see below) GPIO10
Relay none
Temperature (NTC) none found
  • The boot log names the meter (BL0942) and its calibration. The stock firmware sets it up with register 0x19 (MODE) = 0x8F and 0x14 = 0x33; ESPHome's bl0942 does not expose these, so the no-load behaviour can differ from stock.
  • GPIO10 is the multiplexed CF/ZX pin of the BL0942. Stock firmware uses it as a falling-edge interrupt input. After a reset the pin carries the energy pulse (CF); it follows the zero crossings only if register OT_FUNX (0x18) is set to 2. The Plug PM image has no zero-cross code and no caller that selects mode 2, so the pin most likely stays on CF. This was not measured. ESPHome's bl0942 does not use the pin.
  • No ADC pin was found in the firmware, so there is probably no NTC. Apart from the UART transmit pin and the LED data line, the app configures no output pin.
  • The calibration values in the device's shelly partition (voltage, current, power, energy scale) are not used by a plain bl0942 config. Compare the readings with a reference meter and adjust.

Flash it

  1. Install the requirements (once):
pip install -r requirements.txt
  1. Fetch the official package:
python ota.py fetch PlugPMG3 --insecure
  1. Build: put your app into it; the ZIP goes to out/:
python ota.py build PlugPMG3 app.ota.bin --esphome-factory app.factory.bin --esphome-yaml app.yaml
  1. Check the device first. Nothing is sent:
python ota.py send PlugPMG3 out/PlugPMG3-app-<date>.zip --ip <device IP> --dry-run
  1. Flash it (the log goes to a file with --log-file):
python ota.py send PlugPMG3 out/PlugPMG3-app-<date>.zip --ip <device IP> --log-file

app.ota.bin and app.factory.bin are the two files ESPHome compiles. --dry-run only checks the device and, for this package, reads the update target slot. Command reference: Commands.

fetch needs Shelly's update API to answer with a download URL for PlugPMG3. The profile's update_id is the app name found in the image; it is assumed, not confirmed, that the update API uses the same name. If fetch fails with "No https 'url' in update API reply", get the official 2.0.1 package another way and give it to build with --official <ZIP>.

What to expect

send shows these lines at the default log level, in this order:

# Log line Meaning
1 Update target slot: 0 ... The slot check of send. Anything else: run python ota.py restore PlugPMG3 first
2 Device: The bootloader will be replaced ... (raw log: Boot: cur ... min ... update? 1) The installer will write ESPHome's bootloader. WARNING: ESPHome's bootloader was NOT written (update? 0) means it will not: build again with a higher --boot-min-version (why)
3 The progress (Update: ... %, one line that updates in place) up to 100 %, then Done: update installed, the device confirmed it The device restarts into ESPHome

Please report what you see, also when it works: open a device report. The lines Update target slot, Boot: cur ... update? and Will write to slot are the ones that matter, and whether the plug measures voltage, current and power afterwards.

Notes for this device

  • The profile sets boot_min_version: 1.0.9. The plug runs Shelly OS loader 1.0.3 (boot log), so the default (one patch above the official loader, 1.0.3) would be skipped by the installer, and later ESPHome OTAs would not take effect. Same cause as on the H&T Gen3 and the Plug M Gen3.
  • No relay means nothing in the config switches a load. The button can only be a binary sensor.
  • Check the app name (PlugPMG3) and the model (S3PL-30116EU) before you use this page: the Plug M Gen3 (PlugMG3, S3PL-30110EU) looks similar but has a relay and other partition sizes.

Way back

python ota.py restore PlugPMG3 sends the official firmware back while Shelly firmware still runs.

The UART steps on that page were run on a Plus Plug S and a Plug M Gen3. For this plug the parts and addresses come from the official package's manifest and partitions/PlugPMG3-stock.csv; the command below is derived from them and has not been run on a Plug PM Gen3. The only difference to the Plug M command is the file system, which sits at 0x2a0000 here (0x2c0000 on the Plug M):

esptool --chip esp32c3 --port COM4 --baud 460800 erase-region 0x14000 0xc000
esptool --chip esp32c3 --port COM4 --baud 460800 write-flash --flash-mode keep --flash-size keep --flash-freq keep 0x0 bootloader.bin 0x10000 partition-table.bin 0x11000 boot_state.bin 0x20000 PlugPMG3.bin 0x2a0000 fs.img

Do not write the shelly partition (0x7f0000): it holds the model name and the calibration of this plug, and no package contains it. A plug restored this way reports loader 1.0.3 afterwards, which is why the profile sets boot_min_version: 1.0.9.

Warning

  • Wipes Wi-Fi and settings. ESPHome opens its own access point or joins the Wi-Fi from your config; if nothing comes up, power-cycle the device (help).
  • No way back over the network once ESPHome's bootloader runs: restore gets no answer, only UART brings Shelly OS back (Recovery over UART). Take a flash backup first if you can.
  • Flashed it? Tell us, also when it worked: open a device report.

Bootloader and slots · Troubleshooting · Recovery over UART