Attention!!! 0.0.6 changed some of the pins and is not 100% compatible anymore. Please keep in mind, when using the ESPhome YAML or when implementing your own firmware.

If you need to assemble a few parts (ECAPs and optional stuff) or flash another firmware, watch my video on YouTube.


At first, do not get confused, KM217 and KM271 ist the same, I just had a number swap in and it is simply impossible to change all the historic stuff and naming 🙁

If you ordered the module described in Reverse Engineering the Buderus KM271 – And Making It WiFi-Flying on ESPhome and Home Assistant from my Tindie store or built it on your own, this is the place to search for, when it comes to getting it up and running. You will find the Information for both versions (0.0.5 and 0.0.6 here). Version 0.0.6 is already available and can be ordered.

Known compatible Heating Control Units

  • Buderus Logamatic 2107 M (this is my own unit)
  • Logamatic HS2102 (not EcoMatic !!!)

If you have one of my boards and a different control unit that works, please tell me about, so I can add it to this list 🙂 If you are not 100% sure, I have still plenty of old bare 0.0.5-Boards for a very low price. Antoher option is to print one of the PCB pages with 1:1 scale, glue it on a cardboard cut it out and test if it fits in your heating controller.

The Hardware

To make your life easier for aseembly and to find the parts and signals, here is the interactie BOM.

The Software

There is a ton of software alternatives for the board, but I’ll only describe three of them in more detail. You can select the firmware when you order the board.

Default, no FW selected: Blinkenlights

At first, I’ll just tell you, what is on the board, when you did not select any firmware during your order on Tindie. It is a simple test program, that ensures, that the ESP32 and the LEDs are working.

It does nothing more than rolling through the 4 LEDs on the board.

It will be possibly extended in future to catch hardware and assembly bugs, should they arise in future.

You can find it on GitLab. Use VSCode with PlatformIO to open, compile and flash it. This is also a very nice foundation for developing your own firmware.

Flashing can be done, by connecting power, ground, RX and TX. IO0 and EN is not needed and can be triggered with the buttons. Press BOOT and keep it pressed, shortly press RESET and start your flash tool. Then release BOOT and flashing will start.

I’ll possibly improve the Blinkenlight to be able to update the board via WiFi or BLE. If you feel responsible to do this, I would be happy to take the pull request. If I get a working firmware, the minimal thing I would do is refunding the board you bought from me 🙂

Sven’s great MQTT-firmware

Sven published a firmware on GitHub for my module that speaks MQTT on the network. This was probably the most complete piece of code for my module before JEns accepted the challenge on the ESPhome part. The „only thing“ you need to do is installing VSCode and the PlatformIO addon, set the credentials for WiFi, MQTT and OTA (in include/Credentials.h), compile and flash it to the board.


If you selected ESPhome, you will get an (older) ESPhome firmware version for this board. But as you will update the firmware after adjusting the config, you will have the latest firmware aligned with your ESPhome instance. Currently, the firmware is likely to be feature complete and runs without problems. See the section below, ho to connect to your board.

Diggers Full Example YAML (Drop Down Accordeon)

  name: buderus-km217
  platform: ESP32
  board: esp32dev

# Enable logging

# Enable Home Assistant API

  password: "XYZ"

  ssid: !secret wifi_ssid
  password: !secret wifi_pass

  # Enable fallback hotspot (captive portal) in case wifi connection fails
    ssid: "Fallback Hotspot"
    password: "XXX"


  id: uart_bus
  tx_pin: GPIO2
  rx_pin: GPIO4
  baud_rate: 2400

#  - source:
#      type: local
#      path: my_components/components
#    components: [ km271_wifi ]
  - source: github://the78mole/esphome_components@main
    components: [ km271_wifi ]

  - id: budoil
    uart_id: uart_bus

# SPI starting from version 0.0.6
  clk_pin: GPIO18
  mosi_pin: GPIO23
  miso_pin: GPIO19
  id: bus_spi1

# nCS for SPI is GPIO15

  sda: GPIO13
  scl: GPIO16
  scan: true
  id: bus_i2c1

# For version 0.0.6
# For triggered actions, I2C devices can use GPIO14
# To enable the I2C level shifter (I2C_EXT_EN), use GPIO 12

  id: ledgn1
    number: GPIO21
    inverted: true

  - platform: km271_wifi
      name: "Warmwassersolltemperatur Tag"

  - platform: template
    name: "Warmwasser Betriebsart"
    id: warmwasser_betriebsart
    entity_category: config
    optimistic: true
      - Dauerhaft aus (0)
      - Dauerhaft ein (1)
      - Automatik (2)
    initial_option: Automatik (2)
      - lambda:
          auto index = id(warmwasser_betriebsart).index_of(x);
          if (index.has_value()) {
            uint8_t command[] = {0x0C, 0x0E, (uint8_t)index.value(), 0x65, 0x65, 0x65, 0x65, 0x65};
            budoil->writer.enqueueTelegram(command, 8);

  - platform: km271_wifi
      name: "KM271 Kesselfehler"
      name: "KM271 Kesselbetrieb"
      name: "KM271 Ladepumpe"

  - platform: km271_wifi
      name: "KM271 Vorlaufsolltemperatur"
      name: "KM271 Vorlauftemperatur"
      name: "KM271 Warmwassersolltemperatur"
      name: "KM271 Warmwassertemperatur"
      name: "KM271 Kesselvorlaufsolltemperatur"
      name: "KM271 Kesselvorlauftemperatur"
      name: "KM271 Außentemperatur"
      name: "KM271 Raumsolltemperatur"
      name: "KM271 Heizkurve -10 °C"
      name: "KM271 Heizkurve 0 °C"
      name: "KM271 Heizkurve +10 °C"
      name: "KM271 Brennereinschalttemperatur"
      name: "KM271 Brennerausschalttemperatur"

  - platform: wifi_signal
    name: "KM217 WiFi Signal Sensor"
    update_interval: 60s

  - platform: adc
    pin: 36
    unit_of_measurement: "V"
    name: "KM217 5V Supply"
    accuracy_decimals: 2
    update_interval: 5s
    attenuation: 6dB
      - multiply: 27.7317
      - throttle_average: 60s
  - platform: gpio
    name: LED2_Green
      number: 22
      mode: OUTPUT
      inverted: true
  - platform: gpio
    name: LED3_Yellow
      number: 17
#     number: 23  # For 0.0.5
      mode: OUTPUT
      inverted: true
  - platform: gpio
    name: LED4_Red
      number: 25
      mode: OUTPUT
      inverted: true

Connecting to the board

I configured the ESPhome firmware to run a captive portal after approx one minute. So, after powering the board, you could (after one minute) connect to the SSID „Fallback Hotspot“. Turn of your cellular internet (it disturbs the WiFi very often) and select the Fallback (password is "Z8zfajgxVvNw"). When WiFi of your phone is connected (sometimes you need some tries), a pop-up should ask you to sign in to the network. Follow this. It will present the portal of the ESPhome firmware and show you all WiFis it has found. Select the appropriate one and enter the password of this WiFi.

When the module is correctly connected to the network, it should soon show up as a new ESPhome board in your Home Assistant. Sometimes, you need to wait for a few minutes for the notification to show up. When adopted, you will see it in your ESPhome devices overview and can enter adjust the YAML to your needs. New sensor nodes will also take a few minutes to be shown sometimes.

The relevant part of the YAML is as follows:

  name: km217-for-friends
  platform: ESP32
  board: esp32dev

# Enable logging

# Enable Home Assistant API


  ssid: "<YOUR WIFI SSID>"
  password: "<YOUR WIFI PASSPHRASE>"

  # Enable fallback hotspot (captive portal) in case wifi connection fails
    ssid: "Fallback Hotspot"
    password: "Z8zfajgxVvNw"

Other Settings

Renaming the module should be done using ESPhome GUI

For more detailed information, see my blog about the development of the module.

Using Arduino with MQTT

Coming soon 🙂

5,0 von 5 Sternen (basierend auf 21 Bewertungen)
Sehr gut0%


10. Januar 2024

Was soll ich sagen, ausgepackt, eingesteckt, Wlan ausgewählt und es funktioniert.

Auch perfekt mit der Logomatic 2107 „ohne M“.

Vielen Dank sp spare ich mir den ständigen Weg in den Keller 🙂



5. Januar 2024

Hi, ich weiss dass diese Betrieb und div störmeldungen auch über den Bus kommen. Bei einer Ölheizung hat dies aber einen Haken. Über den Bus kommt brenner Betrieb mit anziehen des Relais wenn T1 T2 Signal an den feuerungsauromaten gibt. Dann startet aber erstmal ölvorwärmung. Erst dann kommt luftumwälzung brennraum, Einspritzung und Zündung. Erst dann gibt der feuerungsautomat famme stabil als Betrieb zurück. Dies wertet die logamatk aber nicht aus. Auch direkte Störung feuerungsautomat aufgrund fall ignition oder Flame cut kriegt die logamatik nicht direkt mit [230v Signale aus dem feuerungsautomaten] deshalb bei mir die koppelrelais. Von mir stammte 2016 die python Variante mit km271 für die logamatik und die Fehler bekam ich nur extern hardwaremässig erfasst


Antwort von MolesBlog

Hallo Michael,

OK, so genau hatte mir das noch nicht angeschaut. Ich weiß nur, dass die Brennerstörung in meinem SmartHome korrekt ankommt und dieses mir dann eine Nachricht schickt.



Sehr gut aber noch eine Frage

2. Januar 2024

Ich habe da auch eine Frage: Ich möchte 2 potentialfreie Relaiseingänge zusätzlich einlesen und über MQTT übertragen.

(Über ralais ausgekoppelte Brenner in Betrieb und Flammstörung)

Version ist die 0.0.7 mit der MQTT Firmware.

Lässt sich dieses so realisieren ?

Gruss, Michael


Antwort von MolesBlog

Hallo Michael,

das ließe sich so realisieren. Du könntest die potenzialfreien Kontakte an den Sensor-Header (J6) oder auch an den Extension-Header (J7) anschließen. Beim Sensor-Header würde es sich anbieten, Pin 6-3 und Pin 4-3 über den potenzialfreien Kontakt zu brücken. Das zieht dann den ADC1_CH5 bzw. ADC1_CH6 des ESP32 gegen Masse. Allerdings sollten Dir die Zustände auch schon über die Parameter zur Verfügung stehen, die über den Bus gesammelt werden…

Beste Grüße,