nrf52840 can be used for asset tracking?

[Neeraj Dhekale]

Hello,

I am new to Nordic, I was previously using Cypress CYBT343026-01. But there were some drawbacks found during development.

1. It was consuming 315μA at 0 dBm BLE tx(1024ms).

2. When deep sleep is used it wakeups by rebooting the controller and it was giving a spike in the current during reboot of 13mA. which is 41 times higher than 315μA.

3. I2C HW buffer is 64 bytes. In that slave address is 1 byte. So maximum payload is 63 bytes. (this is on low priority.).

I am looking nRF52840 for asset tracking and expecting a minimum of 1 year backup of BLE5.0 or above Tx (500-1024ms) at 0dbm without any deep sleep.

I saw the datasheet of nRF52840 and in that "Applications" section I don't see it can be used for asset tracking. So my question is that can I use this nRF52840 for asset tracking? or you suggest any other controller for this purpose?

I saw an Online power profiler for BLE and I have calculated CPU takes 35.1μA + BLE tx at 0dbm 32μA = 67μA total average consumption. is this is correct?

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

[Hung Bui]

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. 

[daviddedwin]

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

[Neeraj Dhekale]

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

[daviddedwin]

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

[Hung Bui]

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. 

[Hung Bui]

Thanks David :)