Using Const Variables Makes Current Goes Up

RE: Using Const Variables Makes Current Goes Up

PB — Thu, 11 Aug 2022 14:42:20 GMT

I think you should look for -mfloat-abi=soft -msoft-float in your project makefile. Likely it's set to "hard" which enables the FPU. At leat that's something which helped me with similar issue. There should be some examples in the nRF SDK which will help with all the flags magic.

Best regards,
PB

RE: Using Const Variables Makes Current Goes Up

Emile — Wed, 27 Jul 2022 15:54:09 GMT

Well the power consumption seemed to be due to the fact that my const array was stored as float. I changed it to double and the problem seems to be gone. What could explain this rise in power consumption? Was it because other section of the CPU was enabled for this operation when the array was stored as a float?

Thank you!

RE: Using Const Variables Makes Current Goes Up

Kenneth — Wed, 27 Jul 2022 13:20:08 GMT

Check out:
https://infocenter.nordicsemi.com/topic/errata_nRF52832_Rev2/ERR/nRF52832/Rev2/latest/anomaly_832_87.html#anomaly_832_87

If you are using the softdevice you should always use sd_app_evt_wait(), not __WFE() directly.

Kenneth

RE: Using Const Variables Makes Current Goes Up

Emile — Tue, 26 Jul 2022 16:06:35 GMT

In fact, I changed the const windows for a calculated window:

void hamming_windowing(int16_t *signal, uint32_t size)
{
   int i = 0;
   for (i = 0 ; i < size/2; i++)
   {
       hamming_element = 0.54 - 0.46 * cos(2*3.1416*i/(size/2-1));
       signal[i*2] = signal[i*2] * hamming_element;
   }
}

I still get the same high current consumption. So doesn't seem to be related to the fact that my array was declared as const. It seems to be related to soft device. When I use sd_app_evt_wait(); in my super loop, I get a high power consumption after the operation. When I change sd_app_evt_wait(); for:

__SEV();
__WFE();
__WFE();

And I disable soft device, I don't have this problem.

Then I try this sleep in my super loop :

__SEV();
__WFE();
__WFE();
nrf_drv_wdt_channel_feed(m_channel_id); // Kick Watchdog
sd_app_evt_wait();

But SEV, WFE, WFE with softdevice enable seems to make current goes to 800 uA. So how can a simple operation in my code with soft device enable makes current consumption go up?

Thank you!