Abstract:

This video demonstrates how to build a low-cost, DIY Apple AirTag alternative by emulating the Apple AirTag's advertising data using the Open Haystack project. The core of the device is a Telink TLSR825x microcontroller, specifically a TB-03F module, which is readily available for a minimal cost. The creator outlines the process of flashing custom firmware onto the chip using a USB-to-UART converter, emphasizing the specific pin connections required for flashing (DTR/RTS to reset, TXD to SWS, VCC, GND). While the project provides a simple, bare-minimum firmware that allows the device to be tracked by Apple's Find My network (requires an Apple device/MacBook), it notes the necessity of providing a unique public key for the firmware. Once flashed and powered by a CR2032 coin cell, the device operates with extremely low power consumption (~10 microamperes), enabling a long battery life for continuous advertising.

Building a DIY Apple Find My Device with Open Haystack

• 0:00 Introduction to DIY AirTag: The video introduces a method for creating a low-cost DIY Apple AirTag alternative.
• 0:12 Open Haystack Implementation: The project leverages the Open Haystack implementation to emulate Apple AirTag advertising data, making the device discoverable by Apple's Find My network.
• 0:23 Setup Requirements: Using the device isn't straightforward on Windows, often requiring an Apple device (iPhone, MacBook) or a server setup for full functionality.
• 0:46 Required Components:
  • A Telink TLSR8252 or similar microcontroller (e.g., AI-Thinker TB-03F module, costing around €1.50).
  • A CR2032 battery holder for power.
  • A USB-to-UART converter (like a WCH chip, with DTR/RTS pins for reset functionality).
  • A soldering iron, solder, and a PC with Web Serial support (Chrome recommended).
• 2:14 Flashing Connections:
  • Connect the DTR or RTS pin of the USB-to-UART converter to the microcontroller's reset pin.
  • Connect the TXD pin of the converter to the SWS (flashing/debugging) pin.
  • Ensure Ground (GND) is connected to GND and VCC to VCC (using 3.3V to avoid damage).
• 3:00 Compatible Microcontrollers: Other Telink TLSR series microcontrollers, such as those found in Xiaomi thermometers or e-paper displays, can also be used.
• 4:34 Flashing Procedure:
  • Access a specific web-based flasher tool (link provided in video description).
  • Input a unique public key (obtained from the Open Haystack manual) into the tool.
  • Connect the USB-to-UART converter, select the correct COM port, and initiate the flashing process.
  • The NRF Connect app can be used to observe the device's advertising once flashed.
• 6:44 Final Assembly: After flashing, disconnect the USB-to-UART converter and desolder the temporary connections. Then, solder the battery holder's VCC and GND wires to the corresponding pins on the TB-03F module.
• 8:16 Power Consumption & Operation: The device starts advertising immediately upon battery connection. It draws a very low current (~10 microamperes), enabling long battery life. The device advertises at approximately 200ms intervals.
• 9:03 Minimal Firmware: The device uses a "bare minimum" firmware, focusing solely on advertising the Find My signal without additional GPIO or complex features.