This video details the analysis, custom firmware development, and flashing process for the SR08 smart ring, a Bluetooth Low Energy (BLE) enabled device featuring fitness tracking capabilities and a unique tiny LED display. The ring utilizes a Dialog DA14584 microcontroller with a surprisingly large 1MB external flash, facilitating custom firmware updates. The presenter demonstrates the fragility of the ring during disassembly and highlights the significant challenges encountered in the development process, including the lack of direct debug access on the ring itself and the necessity of a specific Renesas (formerly Dialog) development board. A custom bootloader and a Python script were developed to overcome firmware flashing limitations imposed by the manufacturer's modifications to the Over-the-Air (OTA) update header and the larger flash size. The video provides a step-by-step guide on flashing a custom demo firmware, which showcases basic display control and touch sensor interaction, and notes its low power consumption in sleep mode. All necessary source code, tools, and documentation are made available on GitHub to encourage community development, despite the presenter's personal challenges with the complex development cycle.
Summarizing the SR08 Smart Ring: Disassembly, Firmware, and Flashing Challenges
0:02 SR08 Smart Ring Overview: The video introduces the SR08 smart ring, a Bluetooth Low Energy (BLE) device featuring fitness tracking (step count, heart rate), a tiny LED display, and a Dialog DA14584 microcontroller with 1MB of external flash memory.
1:35 Disassembly & Fragility: The presenter showcases multiple disassembled rings, highlighting how easily they break, making development challenging due to the high risk of damaging the device.
2:00 Development Hurdles: Direct debug access to the ring is not possible. Successful development requires a specific Dialog/Renesas DA14584 development board (β¬35).
2:45 Flash Memory Mismatch: The development board's stock SPI flash (256KB) is too small for the ring's 1MB flash, necessitating a replacement flash chip and a modified bootloader to support the larger size.
3:12 GitHub Resources: A custom firmware repository is provided on GitHub, including a pre-compiled demo firmware, stock firmware, datasheets, pinout details, and essential tools.
3:38 Custom Tools for Flashing: The repository includes a Python script to create the correct Over-the-Air (OTA) update header (due to manufacturer changes) and a modified bootloader (JTE programmer.bin) to enable flashing the larger SPI memory on development boards.
4:24 Over-the-Air (OTA) Flashing Process: A detailed guide on flashing custom firmware using the Renesas Suota Android app is provided. Users must select the firmware files and ignore a CRC error message (a known issue due to manufacturer modifications).
5:38 Custom Firmware Features & Power Consumption: The demo custom firmware allows turning the LED display on/off via the touch button. It draws approximately 3mA when active and significantly less (18-19 microamperes) in sleep mode, ensuring long battery life.
6:13 Reverting to Stock Firmware: The video demonstrates how to easily flash the original stock firmware back onto the ring using the same OTA method.
7:16 Advanced Development & Debugging: For more in-depth custom firmware development, the presenter strongly recommends using a development board with serial output, enabling detailed debugging and power consumption measurement.
8:30 Conclusion on Development: The presenter expresses excitement for the custom firmware but acknowledges the "painful" development cycle, inviting others to contribute to the open-source project.