Power modes in nrf51822

RE: Power modes in nrf51822

mikelugarte — Tue, 21 Feb 2017 08:02:46 GMT

I finally got to put my nRF51822 in system off mode. Now the current is about 4.5uA. Thanks for the answer!!

RE: Power modes in nrf51822

mikelugarte — Fri, 17 Feb 2017 13:56:28 GMT

Hi, I see that the function sd_power_system_off() needs the softdevice. If I compile it as default, do I need to merge it with the soft device .hex file?

RE: Power modes in nrf51822

bjorn-spockeli — Wed, 15 Feb 2017 09:59:57 GMT

You will have to use the sd_power_system_off()function to enter System OFF which is declared in nrf_soc.h, see this mBed forum post. Power Down is equivalent to System OFF, i.e. everything is powered down except the wake-up circuitry. Deep sleep would be equivalent to System ON: Low power mode, which is entered by calling ble.waitForEvent(), see this mBed forum post for more information.

RE: Power modes in nrf51822

mikelugarte — Wed, 15 Feb 2017 09:25:28 GMT

So how is the system off mode called in mbed?

And deepsleep, power down... are all power modes inside the system ON mode?

RE: Power modes in nrf51822

bjorn-spockeli — Wed, 15 Feb 2017 09:13:32 GMT

The nRF51 series has two power modes, System OFF and System ON, where System ON has a low power sub mode. The section below is quoted from the nRF51 Reference Manual, found here.

System OFF mode

System OFF is the deepest power saving mode the system can enter. In this mode, the system’s core functionality is powered down and all ongoing tasks are terminated. The only mechanism that is functional and responsive in this mode is the reset and the wakeup mechanism.

The system can be woken up from System OFF mode either from the DETECT signal (when active) generated by the GPIO peripheral, by the ANADETECT signal (when active) generated by the LPCOMP module, or from a reset. When the system wakes up from OFF mode, a system reset is performed.

System ON mode

System ON mode is a fully operational mode, where the CPU and all peripherals are brought into a state where they are functional. In System ON mode the CPU can either be active or sleeping in the low power sub mode. The CPU enters sleep by executing the WFI or WFE instruction found in the CPU’s instruction set. In WFI sleep the CPU will wake up as a result of an interrupt request if the associated interrupt is enabled in the NVIC. In WFE sleep the CPU will wake up as a result of an interrupt request regardless of the associated interrupt being enabled in the NVIC or not.

The system implements mechanisms to automatically switch on and off the appropriate power sources depending on how many peripherals are active, and how much power is needed at any given time. The power requirement of a peripheral is directly related to its activity level.The activity level is usually raised and lowered when specific tasks are triggered or events generated, see individual chapters describing the different peripherals for more information on how to optimize power consumption in System ON mode.

Best regards

Bjørn