The SparkFun Portability Shield adds all the user interface bits needed to take a SparkFun development board into the field. A LiPo battery connector, charger, fuel gauge, and an on/off switch address your power needs. A friction-fit microSD connector allows for data logging. The 1.3in. OLED and a five-way navigation switch provide an excellent user interface. Locking 0.1in. headers along the shield's edge make it easier to solder male pins in place.

I²C is used to interface with the display, fuel gauge, and five-way navigation switch (GPIO expander PCA9554). SPI is used to communicate with the microSD card. The power switch uses an ideal diode (LM66200) to disconnect the battery from the system for a sleep current of approximately 4μA.

The Portability Shield has been designed to be usable with any compatible main board, with the RTK Postcard being the first! It’s important to note that the RTK Postcard is designed to have full functionality when combined with the Portability Shield!

• 1.3in. OLED Display
  • 7-bit Unshifted Address: 0x3D (default), 0x3C
• Input Voltage
  • 5V via LiPo or VIN
• Power Switch: ON/OFF
• Five-Way D-Pad Navigation
• MCP73831T Single Cell LiPo Charge IC
  • Charge Rate Set to ~500mA
• MAX17048 Fuel Gauge
  • 7-bit Unshifted Address: 0x36
• AP2112K 3.3V Voltage Regulator
• PCA9554 I²C 8 GPIO Expander
  • Interfaces with 5-way navigation switch and microSD card detect
  • 7-bit Unshifted Address: 0x20
• microSD Socket Friction Fit
• 2.2kΩ Pull-Up Resistors
• Jumpers
  • D/C - OLED I²C Address
  • I²C Pull-Up Resistors
  • PWR - Power LED
  • CHG - Charge Status LED
• Board Dimensions
  • 43mm x 43mm

• Schematic
• KiCad Files
• Board Dimensions
• Hookup Guide
• Hardware GitHub Repo