[TW#15834] ulp_adc current measurment is not correct

[baoshi]

In the examples\system\ulp_adc
The claimed current draw @ 10Hz is 80uA
I found it is can be much less at round 39uA (below scope capture from uCurrent, 1mV=1uA)

This is possibly because GPIO15 has internal PU enabled but the pin is grounded to suppress boot message.
Add
rtc_gpio_pullup_dis(GPIO_NUM_15);
at beginning of the code resolves this issue.

[igrr]

Just to clarify, do you get 39uA with or without this extra rtc_gpio_pullup_dis line?

[baoshi]

Without rtc_gpio_pullup_dis, with GPIO15 tired to gnd-> 80uA
With rtc_gpio_pullup_dis, without GPIO15 tired to gnd -> 39uA
With/without rtc_gpio_pullup_dis, GPIO15 floating -> 39uA

[negativekelvin]

Avg current with spikes probably at least +10uA?