nrf52840 can be used for asset tracking?

RE: nrf52840 can be used for asset tracking?

Hung Bui — Tue, 22 Dec 2020 09:58:06 GMT

Thanks David :)

RE: nrf52840 can be used for asset tracking?

Hung Bui — Tue, 22 Dec 2020 09:33:02 GMT

Hi,
Could you explain why you have to add 35.1uA into the calculation ?
What you see in the online power profiler is included the CPU and all peripherals needed for the radio operation. You don't need to add anything.
We only have one deep sleep mode called SYSTEM OFF. This turns off all peripherals and CPU except for GPIO interrupt to wakeup. I would assume you don't plan to use this mode as it doesn't have a timer.

In System ON sleep mode we turn off CPU but can keep other peripherals. This mode is already calculated in the online power profiler.
I would suggest you to get hold of a Power Profiler Kit to measure the actual current consumption.

RE: nrf52840 can be used for asset tracking?

daviddedwin — Tue, 22 Dec 2020 06:44:45 GMT

67uA for the average current appears reasonable.

"Deep sleep" is not the word that is used in the nRF52xxx series, I think the equivalent is System OFF, wakeup on GPIO (RAM retention can be ON or OFF based on the needs of the designer), see section 18.2 System OFF mode in the nRF52832 PS.
and section 18.8 Reset behaviour

I would definitely expect the CPU to be reset when coming out of a System OFF mode the table in section 18.8 also shows that. There will be an inrush of current (a spike) when the IC moves out of system OFF but your decoupling caps will filter and smoothen it out.

I don't remember the measurements for this specific one.

I see some measurements here but I think they have not removed the decoupling caps devzone.nordicsemi.com/.../power-on-reset-on-nrf52832

RE: nrf52840 can be used for asset tracking?

Neeraj Dhekale — Mon, 21 Dec 2020 23:13:16 GMT

Thanks for this information.

67μA Is this approx current calculations are correct?

Do nRF52840 wakeup from deep-sleep by rebooting the controller?if yes, then how much current does it consumes during reboot?

RE: nrf52840 can be used for asset tracking?

Neeraj Dhekale — Mon, 21 Dec 2020 23:01:55 GMT

Yes that’s correct. It was seen on cypress’s CYBT-343026-01.

RE: nrf52840 can be used for asset tracking?

daviddedwin — Mon, 21 Dec 2020 17:33:14 GMT

Hey Hung, The 13mA is what was seen for the cypress device. Neeraj Dhekale Is that correct ?

RE: nrf52840 can be used for asset tracking?

Hung Bui — Mon, 21 Dec 2020 14:07:32 GMT

Hi Neeraj,

The online power profiler can provide a quite close to realistic number.

The spike of 13mA is high, you may want to use a Power Profiler Kit to measure and find what exactly caused that spike.

Please describe a little bit more on the asset tracking application you are building.

RE: nrf52840 can be used for asset tracking?

daviddedwin — Sun, 20 Dec 2020 18:52:08 GMT

The nRF52840 can be used for asset tracking but its a larger and more expensive IC. It would be simpler to start with the nRF52832 and then check if you can fit inside the nRF52810 for your application. Yes, your calculations for average current look ok. Look at the peak currents as well, these seem to be only visually represented, so hover over the bars to look at the peaks.

The numbers reported are average , so look at the peaks visually so you don't miss anything.

Usually asset tracking may use some crypto to ensure that there is no spoofing of the radio packets and some level of replay protection, so you may want to look at the crypto available as well.

By reboot I assumed that you meant the IC starts from the start vector ? usually the Flash, CPU and the 16MHZ(RC at least), All RAM, will run on start, so you add those to get the expected peak currents. Look at section 17. in the nRF52832 PS (v1.4)

You can also run some of the code from RAM, running from RAM will save more power as compared to running from Flash.

Additionally don't forget that the numbers reported may be "typical" so the maximum numbers are likely to be different especially at higher temperatures (higher usually means higher than 25 deg C)