Design for a minimalist smartwatch optimized for month-class battery life and sunlight readability.
| Component / Module | Qty | Purchase Link (JLC Parts) | Datasheet |
|---|---|---|---|
| nRF52840 SoC (Bluetooth MCU) | 1 | JLC C190794 | Download |
| BQ25180YBGR (LiPo Charger) | 1 | LCSC BQ25180 | Download |
| MAX17048G+T10 (Fuel Gauge) | 1 | JLC C2682616 | Download |
| RT6160AWSC (Buck-Boost) | 1 | JLC C7065276 | Download |
| BMA423 (Accelerometer/IMU) | 1 | Mouser BMA423 | Download |
| DRV2605YZFR (Haptic Driver) | 1 | JLC C81079 | Download |
| USBLC6-2SC6 (ESD Protection) | 1 | JLC C2827654 | Download |
| KH-TYPE-C-16P (USB-C Connector) | 1 | JLC C709357 | Download |
| FTC252012SR47MB (0.47uH Inductor) | 1 | JLC C5832368 | Download |
| 2450AT18B100E (Chip Antenna) | 1 | JLC C11022 | Download |
| EVP-AKE31A (Tactile Buttons) | 3 | Panasonic EVP-AKE31A | Download |
| 503480-2400 (E-Paper Connector) | 1 | Molex 503480-2400 | Download |
| MBR0530 (Schottky Diode) | 3 | JLC C475718 | Download |
- Core MCU: Powered by the nRF52840 SoC, an ARM Cortex-M4F processor supporting Bluetooth LE and ultra-low power operation.
- Display Interface: Features an E-Paper Display connected via a 24-pin FPC connector (503480-2400). It uses a specialized E-Paper Drive Circuit for high-voltage pulse generation.
- Motion Sensing: Includes a BMA421 3-axis accelerometer (IMU) for step counting and gesture detection, connected via I2C.
- Tactile Feedback: Integrated DRV2605YZFR haptic driver to provide vibration alerts and tactile user interaction.
- Power Management:
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LiPo Charging: Managed by the BQ25180YBGR IC for safe battery charging via USB-C. Battery Gauging: Uses the MAX17048G+T10 fuel gauge to accurately monitor battery state-of-charge.
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Voltage Regulation: An RT6160AWSC DC/DC buck-boost converter provides a stable 3.3V system rail from the fluctuating battery voltage.
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- User Interface: Three tactile buttons for navigation: SW_UP, SW_ENT, and SW_DN.
- Communication & Debug:
- Antenna: 2.4GHz ceramic chip antenna (2450AT18B100E) for Bluetooth connectivity.
- SWD Interface: TC2030-IDC connector for programming and debugging the nRF52840.
The pins are assigned to optimize low-power peripheral management and shared communication buses:
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I2C Bus (Shared): P0.26 (SDA) & P0.27 (SCL): Shared bus for the IMU (BMA421), Fuel Gauge (MAX17048), Haptic Driver (DRV2605), and LiPo Charger (BQ25180).
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Navigation Buttons: P1.04: Assigned to SW_UP. P1.02: Assigned to SW_ENT. P1.06: Assigned to SW_DN.
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E-Paper Display Control: SPI Interface: Dedicated pins for MOSI, SCK, and CS for fast display updates. P0.11 / P0.12: Control lines for display Reset, Busy, and Data/Command (D/C) selection.
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Power Control: P0.14: Used as an enable signal (TIC_EN) for peripheral power management.
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Debug/Programming: SWDIO / SWCLK: Dedicated hardware pins for Serial Wire Debug.