HackManhattan’s Nordic nRF51822 breakout board
Guan Yang of HackManhattan informs us of his efforts in working with a Bluetooth low energy component:
This amazing component is the Nordic nRF51822 that was released last year and is now available for order from Mouser. It’s a Bluetooth Low Energy system-on-chip that includes a transceiver and a Cortex-M0 microcontroller.
Here’s a breakout board I made for it, using a Johanson balun and chip antenna. It takes a little help from the Internet, but I got it to work with Nordic’s SDK and the gcc-arm-none-eabi toolchain. Haven’t tried debugging yet.
Bluetooth Low Energy (or Bluetooth 4.0) is a new protocol that’s much simpler than traditional Bluetooth and optimized for low duty cycle communication such as heart rate monitors, fitness devices and remote control. For iOS, it has the added virtue that apps can use custom Bluetooth devices directly without requiring special hardware approval from Apple and their MFi encryption chip.
The transceiver inside nRF51822 (96.5 dB link budget) supports both Bluetooth Low Energy and Nordic’s proprietary nRF24L01+ protocol, which everyone and their mother seems to be using in their designs these days. The physical layer makes raw packets are made available in a frame buffer. Nordic provides a free S110 “softdevice” stack that handles the Bluetooth protocol.
The microcontroller is pretty nice too: it includes AES encryption, 12-bit ADC, and a switch matrix that allows you to map almost every digital function to any pin. There’s 256 KB of flash (80 KB of which are needed for the Bluetooth softdevice) and 16 KB SRAM.
With chip antennas and integrated passives, it’s never been easier to realize an RF design. Leaving out the 1.9V DC/DC converter (using the on-chip LDO instead), the minimum circuit for nRF51822 has 6 decoupling caps, one pulldown resistor, a balun, an antenna, a 16 MHz crystal and two load capacitors.
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