cheap bluetoothmodule - would it work?

[pcace]

Hi there,

would this work for the use with openHaystack? NRF52832 @aliexpress
what would be the smallest yet cheap devices wich would work?

Thanks a lot!!

[mishailovic]

currently there is no firmware for that model. In my opinion esp32 is still the best option you can have, and it costs half of the price of the NRF52832 (link)

[dzianisv]

ESP32 consumes to much power, so it is not possible to power it from CR batteries, and I need LiIon battery + DC-DC to 3.3V. Probably firmware could be optimized to be more efficient with a deep sleep.

Here is an article how I built by tracker on ESP32 for more context: https://dzianisv.github.io/notes/Embedded/ESP32-Baremetal-Airtag.html

[krakowski]

Found these cheap bluetooth beacons using nRF51822 : https://aliexpress.com/item/1005003671695188.html

Using a flasher (ST-LINK/V2) it should be possible to flash the nRF51 firmware (https://github.com/seemoo-lab/openhaystack/tree/main/Firmware/Microbit_v1) onto it. Haven't tried it out yet, though.

[dzianisv]

This bluetooth beacon looks amazing.
ESP32 is good and small too, but they consume a lot of energy and need a bigger battery.
Probably firmware is not optimized in the best way...

[dzianisv]

Did anyone try that nRF51822?

[jamine16]

You can flash them with ST-link v2, but you need to convert it to a J-Link using the Asshole.bin firmware from here first

https://github.com/e0r/stm32f103c8t6-jlink

Then you can use the Jflash software.

[Jaykob]

Thanks for the valuable hints!
Can we flash the ST-link v2 through USB or do we need another J-Link in order to flash asshole.bin (nice name 😅)?
That would be a chicken egg problem for me…

[anton7300]

Managed to build openhaystack tracker on nrf51822, https://dzianisv.github.io/notes/Embedded/Nordic-NRF51822-Airtag.html