Default REGOUT0 resgister value not as expected

[Daniel Reisfeld]

Hi,

According to the NRF52840 product specification document the default value for REGOUT0 is 0xFFFFFFFF.

When powering the VDDH this implies that the VDD power is 1.8V 

However, when using own board powered by VDDH (with no debugger attached), REGOUT0 is 4 and VDD is 3V. 

I need the 1.8V behaviour.

Please advise how this could happen and how to get the 1.8V

Thanks,

Daniel

[Øyvind]

Hello,

Can you please elaborate on your setup? Are you using a custom board or a Nordic DK? Has anyone used the board before you?

The REGOUT0 register in the UICR configures the output of REGOUT0. And yes, this is by default set to value 7 = 1.8V. 

What happens if you do:

nrfjprog -f nrf52 --eraseall

Kind regards,
Øyvind

[Daniel Reisfeld]

Øyvind,

I'm using my own boards and downloading using SES and the DK.

I'm now able to describe the phenome as follows:

1. If leaving REGOUT0 untouched it seems Softdevice is changing its value to 4 (and maybe resetting to change to 3V).

2. If changing its value (using nrf_nvmc_write_word) before activating Softdevice (otherwise the program crashes) it seems Softdevice doesn't change REGOUT0 value (also in subsequent runs).

Is this consistent with your knowledge of Softdevice? Does Softdevice indeed changes this register?

If so, is there a way to burn the software (using the DK) without going through actively changing the default and restart?

Thanks,

Daniel

[Øyvind]

Daniel, 

When you say DK, I presume you mean SDK (Software Development Kit) and not Development Kit?

Is this consistent with your knowledge of Softdevice? Does Softdevice indeed changes this register?

The SoftDevice does not change any value for REGOUT0. What FW are you using? Are you programming one of our examples?

If you have already written once to the REGOUT0 register in UICR, then you will need to run

nrfjprog -f nrf52 --eraseall

to remove this value. 

On the boards you are using, what is connected to VDDH?

Kind regards,

Øyvind 

[Daniel Reisfeld]

Øyvind,

I mean development board by DK.

I was able to replicate the problem with the DK (and not only by my board).

The essence of my question is, therefore: it seems that if the REGOUT0 is changed once from its default value (0xFFFFFFFF) it will remain changed in next firmware updates (which means that the firmware update doesn't apply to the relevant flash page.

Moreover,if a customized board is powered by the VDDH, Softdevice will change the default value (at least of burned by the DK using SES).

Can you kindly double check if Softdevice may indeed change REGOUT0. If so, is this behaviour controllable?

Thanks,

Daniel

[Øyvind]

Daniel, 

Please answer all of my questions.

The SoftDevice does not set any value to REGOUT0.

What FW are you using? Are you programming one of our examples?

What is connected to VDDH on the custom board? 

Daniel Reisfeld said:

he essence of my question is, therefore: it seems that if the REGOUT0 is changed once from its default value (0xFFFFFFFF) it will remain changed in next firmware updates (which means that the firmware update doesn't apply to the relevant flash page.

 If you have written once to the REGOUT0, then it will stay like this until an --eraseall is issued.

Kind regards,
Øyvind