Welcome to the Smartwatch Builder Podcast. Today we’re covering how to pick the microcontroller chip. As Eric explains, designing a consumer electronics product is an exercise in “constraint maximization.” In 2011 Pebble used STM32F2 microcontrollers and separate Bluetooth radios, but for Core Time 2 they needed more RAM, better power draw and an open source SDK. After evaluating Nordic’s nRF52840 and newer nRF54 series, they discovered the SiFli SF32LB52J. This custom Bluetooth chip offers over 512K of SRAM, 16M of PSRAM, a dedicated MIP display interface, and ultra-low power consumption—only 50 microamps when connected. Best of all, “their SDK is open source on GitHub,” making porting PebbleOS straightforward. At under two dollars per unit it fits the goal: “an always-on daylight readable display that lasts for 30 days” at an affordable price. Next up, we’ll dive into picking the display. Thanks for listening, and happy building!
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