Xiaomi LYWSD03MMC temp/humidity sensor

Hello, I am one week new to Home Assistant, and face a challenge that I would like to ask some help for. Excuse me if it is a trivial question, and point me in the right direction for more learning in that case :slight_smile: I have a few Xiaomi temperature and humidity sensors, and I would like to use them with HomeAssistant (installed on Raspberry Pi 3B) to monitor temperature in my house. I am having difficulty connecting them. I start with one sensor.

  1. HomeAssistant automatically detects the sensor (impressive UX!), and offers to connect to it.
  2. It asks for a bindkey.
  3. I use the tool at Telink Flasher v7.1 to connect to that sensor, and it works fine (shows the same values as on Xiaomi sensor LCD display). It also gives me a 32-character Mi Bind Key.
  4. When I use that key as the bindkey in HA, it tells me “The provided bindkey did not work, sensor data could not be decrypted. Please check it and try again.”


  1. Why does that TelinkFlasher tool work without me providing any key, but HA needs me to supply a key to read the very same values?
  2. Googling shows that there are two options I might want to investigate: flashing different firmware and using some proxy hardware like ESP. But why would that be needed (or recommended) if, again, TelinkFlasher reads the values just fine out of the box, both on my smartphone and on my laptop?
  3. Is there a generally accepted preferred method to connect those sensors in the end of 2023? I see a lot of material on the web, but I am not sure what of that is recommended today, and what is already outdated. As the first step, I’d like to connect 1…4 sensors I already have. Ideally without buying extra hardware (so that I can start monitoring the new house ASAP). If possible, I’d like to extend it to up to 8…10 sensors in the long term.

Many thanks for your help in advance!

I have converted all LYWSD03MMC here from BT to Zigbee. In case you have a Zigbee network in place just give it a try. Works very reliable so far and no tampering with keys necessary. A good reading about the latter you’ll find HERE.

I have a ton of those that I’ve flashed with the same tool. I had trouble initially but switched them to the BTHome protocol (can’t remember the name of the setting in the flasher) from whatever the default is and they work perfectly.

Thanks Ben, this was a saver. After some more struggle with “standard” protocol, I followed your advice and switched to BTHome, as explained at https://bthome.io/ on the main page. Both devices have been working fine since that moment. The only funny observation I have is that one of them shows, in addition to temp and humidity, mass and both show pressure (?!??!). Not sure how to interpret those yet :slight_smile:

Glad it helped!

Weird. I have several dozen that I’ve slowly collected and none of them have had those sensors.

Hi!I also have this heater but now it asks for the bind key, i used the extractor tool but it doesnt work any reason why?

You can get the bindkey from the flashing tool.

I entered the site Telink Flasher v7.4

But doesnt detect the heater, it asks for bluetooth connections but the heater uses wifi i think.

Whats the flashing tool?

Is that a typo? This post is about a temp/humidity sensor.

The heater has a humidity and temp sensor inside. Its being detected by home assistant.

That flashing tool and this thread is specific to the Xiaomi LYWSD03MMC temp/humidity sensor. Is there a reason you thought it would work with your heater?