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atc1441 / ATC_MiThermometer

Custom firmware for the Xiaomi Thermometer LYWSD03MMC and Telink Flasher via USB to Serial converter
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LYWSD03MMC - can't connect after enabling "LE Long Range" even with BT5 USB adapter #296

Open tomwaldnz opened 1 year ago

tomwaldnz commented 1 year ago

I use a half dozen Xiaomi LYWSD03MMC temperature sensors with Home Assistant, they work well. I have an XDO bluetooth 5.0 adapter, which I usually have connected to a Raspberry Pi 4, but also works on my Ubuntu PC.

As an experiment to see if I could get longer range I disabled "BT5+ PHY" and enabled "LE Long Range" on one of my thermometers. I can't connect to that thermometer any more, either with the XDO BT5 adapter, with a modern Samsung phone that also supports BT5, or with a Google Pixel 4a that also supports Bluetooth 5 LE.

The sensors are cheap enough that they can be replaced easily, but I'd like to see if I can get it working again. I'm not interested in cutting up a USB cable and soldering to get a physical serial interface though. Can anyone help? Or have I ticked options in a way that mean it's basically bricked?

Here's the details of my Bluetooth adapter

hciconfig -a
hci0:   Type: Primary  Bus: USB
    BD Address: 00:E0:42:8B:xx:xx  ACL MTU: 1021:6  SCO MTU: 255:12
    UP RUNNING PSCAN ISCAN 
    RX bytes:5737 acl:0 sco:0 events:341 errors:0
    TX bytes:32992 acl:0 sco:0 commands:303 errors:0
    Features: 0xff 0xff 0xff 0xfe 0xdb 0xfd 0x7b 0x87
    Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
    Link policy: RSWITCH HOLD SNIFF PARK 
    Link mode: PERIPHERAL ACCEPT 
    Name: 'RTK_BT_5.0'
    Class: 0x000000
    Service Classes: Unspecified
    Device Class: Miscellaneous, 
    HCI Version: 5.1 (0xa)  Revision: 0xdfc6
    LMP Version: 5.1 (0xa)  Subversion: 0xd922
    Manufacturer: Realtek Semiconductor Corporation (93)
d1scolor commented 3 months ago

Got the same problem

d1scolor commented 3 months ago

OK fixed it by shorting the Reset and Gnd on the pcb (you can see them after you open the backplate sensor, next to the battery). It will uncheck that LE Long Range option. When you successfully short the two (when sensor is powered on), you'll see the screen briefly goes blank and it will restart automatically. After the reset, some of (maybe all of?) the other settings remain unchanged.

tomwaldnz commented 3 months ago

Interesting. I solved the problem by throwing it in the rubbish bin and buying another, but your way seems better :)