This is a small (0.7 in. x 1.4 in.) development board for Nordic Semiconductor's newest System-on-a-Chip IoT solution the nRF52832. The nRF52832 SoC has an ARM Cortex M4F processor running at 64MHz clock speed with a single precision floating point unit. Not only is the nRF52 much faster than the nRF51, but Nordic has significantly improved the peripheral management with EasyDMA and offers sophisticated power management options. There is an embedded balun so only two discrete RF components are needed. I have added a through hole at the end of the antenna trace for soldering a 1.25-inch long (monopole) copper wire which should provide acceptable BLE performance.
The board has a MAX1555 battery charger and a USB Micro-B connector for charging only; the nRF52 has no USB controller. There is a NCP161 450 mA LDO 3V3 voltage regulator providing plenty of current to the board for adding sensors, SD cards, and displays, etc.
There is an MPU9250 9 DoF motion sensor and a BMP280 altimeter on the board connected to nRF52 pins 6 and 7 for SDA/SCL, which are also routed to edge pins. The board breaks out all of the GPIOs except pin 8 (used for the MPU9250 interrupt), and pins 22, 23 and 24 (for the rgb led). I changed the board design slightly to use pin 8 for the MPU9250 interrupt and free up pins 9 and 10 for the NFC in case this might be useful for any applications. Otherwise the board is exactly the same as the previous version.
The board can be powered from the USB connector or via a LiPo battery. There is a switch connecting VBAT to the 3V3 LDO enable which controls power to the board. With the switch on, a green led indicates power on and the board is supplied with 3V3. The battery can be charged while the board is powered and a red led is on while charging. With the switch off, the LiPo battery can still be charged and the green led indicates power good on the USB cable.
Available at Tindie.