High current consumption (1 mA) on UART TX pin 4, but not on all pins !

[ThierryC]

I use nRF52832 and SDK 15.

Using the PPK, I measure a floor of about 1 mA that stay in SYSTEM_OFF mode.

Debugging in more detail, I found that it's due to the UART setup and more precisely when the TX pin is connected to P.04 !

But this pin is not connected externally (only on a connector) and if I run same setup with TX connected to another unused pin (P.25 on my case), this power consumption is gone.

So I suspect another internal resources connected to this P.04 pin, but I cannot find it. Any idea ?

[ThierryC]

Looking more on the issue, it seems not necessary related to UART. If I set this TX pin (P.04 in my case) to "Output High", I got this power consumption, but not if I set it to Input or "output Low". But on the HW, there's (should be) nothing connected to this pin, just a connector.

[Kenneth]

I agree with you, based on the nRF52-DK there is nothing hooked to P0.04. Have you tried to measure with a multimeter if there is any resistance on the pin, and/or if you by software may have added some kind of pull-down on the pin?

What is the revision of the nRF52-DK you are using?

[ThierryC]

Yes, apparently we have some lower resistance on TX in some devices we are using (our prototype, not a DK). We have to understand how it happens.
Anyhow thanks for the hint !