BLE indications

Hello,

I have a Xiaomi MI Scale 2 and I want to read the weight using an MDBT42Q using it's BLE. I've found the protocol defined here: https://github.com/oliexdev/openScale/wiki/Xiaomi-Bluetooth-Mi-Scale

For reading the weight I need to subscribe to the 00002a9d-0000-1000-8000-00805f9b34fb Gatt Characteristic. This characteristic enables me to subcribe to it using indications (not notifications).

I wolud like to know if it's posible to subscribe to indications in a similar way that is used for notifications (startNotifications function).

Thank you in advance.

Hi,

Using startNotifications should 'just work'. It actually checks what the characteristic supports - if it supports notify it does that but otherwise if it does indicate it does that instead... the code where it does this is at https://github.com/espruino/Espruino/blob/master/targets/nrf5x/bluetooth.c#L3293-L3299

Hi,

As part of my research I seen this part of code, so I was confident that the indications will work. The problem appeared when I needed to communicate with the above mentioned device(Xiaomi Mi Scale 2).

The characteristic that I need to use has only set as true the indicate parameter. I've written some code to subscribe using the startNotifications() function, the problem is that I only received one packet of data, after that it seems that the device get stuck as is waiting for the ACK packet necesary to finish the indication reading procedure.

I will try to create using 2 espruino devices an example to do it more reproducible without buying a Scale.

Thank you for your fast response.

Thanks - so you think it's likely Espruino doesn't send the ACK for indications, and that's breaking it for you?

Hi,

Yes, this what I think it's happening. Unfortunately I didn't have time to create a testbench to test it yet. I want to do it, as soon as possible, for sharing with you and try to discover where is the problem.