7 hours ago
- The chip selected for Core Time 2 is the SF32LB52J from SiFli, which features an open source SDK.
- The author is writing a series of blog posts on building a smartwatch, covering chip selection, hardware, and software design.
- A smartwatch comprises three main components: watch hardware, watch software (firmware/OS), and a mobile companion app.
- Designing a smartwatch involves constraint maximization, starting from a target experience goal and breaking it into specifications.
- The most challenging component decisions are the microcontroller (MCU) and the display, with MCU being the focal point for software compatibility, power consumption, and cost.
- Previously used MCUs include STM32F2 and nRF52840; for Core Time 2, a chip with more RAM and processing power was needed.
- SiFli's chip meets all requirements: over 512K SRAM, 16M PSRAM, a dedicated MIP peripheral, ~50uA power consumption with BLE, and costs under $2.
- SiFli offered to help port PebbleOS to their chip, making the SF32LB52J the final choice.