As we noted elsewhere Nordic Semi has just launched its nRF51 Series of multi-mode, ultra-low-power (ULP) wireless SoCs. The first two ICs to debut in the nRF51 Series are the nRF51822, a multi-protocol Bluetooth low energy/2.4GHz proprietary RF SoC, and the nRF51422, the world’s first ANT/ANT+ SoC. Both chips combine flexible RF front ends with ARM Cortex-M0 MCUs—no, not 8051s as you might assume. With 10x the processing power and half the power consumption of Nordic’s previous (2nd generation) chips, they’re indeed ultra-low-power. But the real story is in the software.
SoC vendors often, if not typically require embedded developers to use their proprietary software frameworks in order to take advantage of all the hooks they’ve embedded in their hardware. You need to follow their APIs, compile and link your code with the stacks they provide, and then spend a lot of time trying to resolve unexpected dependencies. Nordic claims to have created a software architecture that cleanly separates application code from the protocol stacks, which they provide as linkable, verified, and qualified binaries. The idea is to enable developers who are familiar with the ARM architecture to develop application code using the Keil, IAR, or other tools with which they’re familiar and not have to wrestle with vendor-specific tools. Nordic relies on calls to ARM’s Cortex Microcontroller Software Interface Standard (CMSIS) library to handle the interface between application code and their chips. The stacks are 100% asynchronous, event driven, and run-time protected so you can’t accidentally blow them up.
Nordic has set out to make the nRF51s series a real platform by making all the chips code compatible and with each group pin compatible. This should enable embedded developers to reuse their code base across multiple hardware platforms—well, OK, Nordic’s, but with the major rollout of chips planned for this family that should eventually cover a lot of devices.
About the chips themselves: the nRF51822 is a flash-based SoC that combines Bluetooth Low Energy and Nordic’s widely used (if not widely touted) proprietary Gazell 2.4 GHz protocol. The chip includes 256 kB of on-chip flash and 16 kB of RAM. Nordic provides a Bluetooth Low Energy stack that requires less than 128 kB of code space and 6 kB of RAM, leaving more than 128 kB of flash and 10 kB of RAM for application code. Included are low-energy profiles, services, and example applications. The nRF51822 draws 13 mA on RX peak and 10.5/16 mA TX peak at +0/+4 dBm with on-chip LDO down to 1.8V.
The nRF51422 is the first single-chip ANT solution. The very small stack requires only 32 kB of code space and 2 kB of RAM, leaving 226 kB of flash and 14 kB of RAM for application code. ANT is primarily intended for ULP sensor and control applications in personal area networks (PANs). It does ad hoc networking and can handle six simultaneous master/slave pairings with a burst speed of 60 kbps. At 16 MHz the MCU draws 4.4 mA while executing from flash; the ANT protocol uses active mode sparingly and can go back to sleep in 2.5 µs.
There are numerous two-chip wireless sensor solutions out there, but Nordic has launched a couple of ULP single-chip implementations that are deserving of a close look. Samples are in limited circulation now, with full sampling planned for September and full production late this year.
The low-power wireless market continues to heat up as the chips power further down. It’s a wide open market where even smaller fish like Nordic Semi can come up with a good product and expect to do well. Best of all we’re still in the early stages of the “wireless revolution.” There are a lot more useful devices, not to mention fun toys, coming along that we’re yet to even imagine.
