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Cortex-M0-Enhanced Wireless SoCs Slash Power Up To 50%

74169-AOslo, Norway: The nRF51822 and nRF51422 wireless SoCs promise to significantly reduce power consumption and boost performance, according to developer Nordic Semiconductor. The SoCs share the same architecture and multi-protocol radio. What separates them is that the nRF51822 integrates a Bluetooth low energy/2.4-GHz proprietary stack, while the nRF51422 contains the ANT/ANT+ stack.

The company says both devices can reduce power up to 50%, plus improve the RF link budget up to 9.5dB, compared to the previous generation. The improvements were made possible thanks to the combination of a new low-power multi-protocol radio alongside a 32-bit ARM Cortex-M0 core.

Nordic made small improvements to the radio current, but the most dramatic upgrade comes from a new power-management scheme. There are no set power modes—blocks in use are powered up via software, while unused blocks remain in sleep mode.

Alongside the new power-management scheme is a Programmable Peripheral Interface (PPI), which minimises the CPU’s active time, thus saving power. In turn, peripherals can operate autonomously and talk to each other without waking the CPU. It also reduces real-time requirements on the CPU.

Introducing the ARM Cortex-M0 core had a twofold impact. It improved the processing speed by a factor of ten, and reduced startup time by a factor of 100 to 2.5µs.

In addition, the devices’ multi-protocol radio was entirely redesigned. It now incorporates EasyDMA, which means it can access data directly from the memory, convert it to packets, and then transmit the packets. An increased output-power range stretches from -20 to +4dBm. The radio’s sensitivity depends on its operational mode. For example, in Bluetooth low-energy mode, it measures -92.5dBm. The 9.5dBm improvement in link budget combines these two specs.

In terms of software, the nRF51 series SoCs clearly separate the application and Nordic-provided stack code (as opposed to older solutions that had a single framework). Not only are the application and stack compiled separately, but dependencies between them have been removed. Bugs in the application code will not affect the stack, or vice versa.

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