Clarification Required on DCC Pin Impacting UART Debugging (nRF52833-QDAA-R)

[Jhakan]

Hello Team,

We are currently using the nRF52833-QDAA-R SoC for our R&D activities and have assembled the board based on Configuration 6. However, we encountered an issue during UART debugging:

• When attempting to debug via FTDI using UART, no logs are observed.

• Interestingly, when we solder the 10 µH and 15 µH inductors along with the DCC pin, the UART logs begin to function properly.

Please note the following:

• We are operating in normal voltage mode.

• The DC/DC converter has not been enabled via register settings.

• As per the datasheet, in this default state, the LDO regulator should be active, and the DC/DC converter disabled.

We kindly request your guidance on how the DCC pin and associated inductors might be affecting UART debugging, and whether we might be overlooking any critical design/configuration aspects.

Attached below are relevant datasheet snippets to support our query. Please review and advise.

Thanks & Regards,
Jhakan.M

[Håkon Alseth]

Hi,

 

It sounds like your firmware enables DCDC.

When the hardware does not have DCDC inductors in place and the firmware writes to the .DCDCEN register, the device will do a full power-on-reset.

 

If soldering on inductors to the DCC pin makes the chip function, it sounds like the firmware needs to be revisited.

Are you using NCS or nRF5 SDK?

For NCS, see here on how to use LDO mode for both newer and older versions:  RE: helloworld and blinky don't work in RAYTEC-MDBT50Q-CX-40. 

 

Kind regards,

Håkon

[Jhakan]

Hello Hakon,
Thanks for your response.

Sure we will check the firmware once, but as stated in the datasheet only the LDO is enabled as default and since we haven't changed any register setting for DC/DC we wanted to clarify.

Kindly state how there is a direct impact for UART debugging and DCC pin .

Thanks & Regards,
Jhakan.M

[Håkon Alseth]

Hi,

 

There is no impact between UART and DCC pin.

Kind regards,

Håkon