Current measurements in low power modes

[sara]

Hello, I am working on a project that uses nrf52832 and I need to put that device and in the system on mode. For that, I want to measure the current in the system on and system off mode which is 1-2 uA and 0.2 uA respectively, but I do not get these values. Can you provide me with the code for which I can measure the current in system on and system off mode to get the above values? I had used ble_app-pwr-profiling example to get the values but I did not get the desired values.

[awneil]

sara said:

I do not get these values

So what values do you get?

And how, exactly, are you measuring?

At these levels, you need to be very careful about how you take the measurements - and to ensure that you are actually measuring just the DUT, and not leakage to other parts of your system ...

[sara]

I get 287.099 uA in system on mode. I am measuring using PPK and measuring only the DUT. I am using ble_app_pwr_profiling example.

SDK used is 15.3.0 

[sara]

Could you please also answer my question on ble_app_uart? 

When I press the button the device does not enter system_off mode as current does not change. Is there anything else which I am missing out? And also how to diasble uart so that I can reduce system on current presently I am getting 2.318 mA.

[Edvin]

One way to disable the uart is to not initialize it. 

Don't press any buttons. Unmodified, the uart will time out and enter system off after 180 seconds, as long as noone connect to it. If you want to shorten the advertising timeout, that is the APP_ADV_DURATION in the ble_app_uart example, which is given in units of 10ms. Also remember to disable the NRF_LOG_ENABLED in sdk_config.h to minimize the current consumption.

[sara]

With NRF_LOG_ENABLED disabled, I got system on current as 2.318 mA. and after 180 seconds it gives 6.979 uA.Still the system on current has not reduced. And when I don't init uart, I get a constant current of 4.483 mA in both system on and off mode.

[Edvin]

remove the printf(). It is probably trying to print using the UART, and therefore can't go to sleep. It is only the one in the main() function that will disrupt your measurement unless you connect to anything.

[sara]

Yes, Its working now. When I commented uart_init() and printf() functions with NRF_LOG_ENABLED disabled, I got current between the peaks as 1.186 uA and after 180 seconds it gives 0.254 uA. 

Thanks Edvin.