• Wrapping it all up

    biemster • 09/23/2024 at 11:29 • 0 comments

    This was a really quick project. Implementing the FindMy advertisement was basically the same as what was done for the Lenze st17h66, and is implemented in https://github.com/biemster/tlsr825x_FindMy

    This repo also contains a small python script that will exchange the dummy key in the firmware with one you control yourself, as generated with the generate_keys.py script in biemster/FindMy.

    Precompiled firmware can be found in both the biemster/FindMy and biemster/tlsr825x_FindMy repositories, so no compilation required to get started with this!

    This concludes the updates here, but there are a couple minor enhancements that can be done which will be tracked in the github repository. For example advertising the battery status can be added, and maybe also key rotation and advertising to the Google FindMy network are three things I might pick up soon.

  • Firmware SDK and toolchain, first success!

    biemster • 09/21/2024 at 17:46 • 0 comments

    In the description I already mentioned that this project might be quite straightforward. Since those are usually famous last words I was prepared for defeat, but no!

    Connecting a programmer to the chip worked already on the second attempt, with the help of a script by @pvvx: https://github.com/pvvx/TlsrComSwireWriter

    I had the pleasure of receiving his help on the FindMy implementation on the Lenze st17h66, and this work on the telink 8250 in the BL7T did not disappoint either. With only 3 wires connected via an USB UART I can read and write the firmware in a pinch.

    Second, the SDK. These are usually not easy to find, and if one is found require extensive modifications to get even a basic blinky out of it. But also here we are in luck: https://github.com/Ai-Thinker-Open/Telink_825X_SDK

    This SDK has instructions on installing the toolchain (tc32) in Chinese, but it's basically just extracting a tarball to /opt and then you're good to go. The example/8258_feature_test is configured to test the power consumption of an advertisement, which is already very close of what I want to do. A simple "make" in that directory will produce a flashable bin in the "out" directory. That's all there is to it!

    The following command will flash this firmware to the BT7L:

    python TLSR825xComFlasher.py -p /dev/ttyUSB0 -t 1200 -r wf 0 ../Telink_825X_SDK/example/8258_feature_test/out/8258_feature.bin

    I had to set the activation time larger than the default 600 ms,  but other than that it runs straight out of the box.

    So with all the technical chores out of the way, now it's time to implement the FindMy advertisement. This is definitely off to a good start!

    EDIT: Victor's repo for the Xiaomi BLE thermometer is a goldmine for info and code for the 825x: https://github.com/pvvx/ATC_MiThermometer