nRF52833 Custom PCB Development Questions

[cheezballs]

Hi there,

I am wanting to develop a custom PCB for the nRF52833 SoC. I am basing it off the nRF52833 DK! As such, most of the schematic labels are identical.

For our custom board, we are wanting to get rid of the interface MCU such that the board is smaller and less resource-intensive. I understand that this interface MCU has the onboard J-Link features to program the nRF SoC with the SWD pins (clock and data). But from reading some other forums on here, I see that it is possible to program custom boards with DK boards using these SWD pins sourced from the SWDIO and SWDCLK pins. I realise that the external board has to have the same input voltage as the DK.

• Are SWDIO and SWDCLK purely used for programming the SoC? Or are they also used for data transfer i.e. UART?
• Can you confirm whether external programming can be done through the SWD pins on the P19 connector as mentioned here?
• It is possible to use an external J-link debugger to connect to the Debug-IN (P18) header on our custom board to program it? Would this J-link debugger be applicable?
• Is it possible to route the UART data transfer through the high-speed nRF USB connector (on the bottom of the board)? Currently, for DK development, the programming and data transfer is being done from the interface MCU USB port (on the left of the DK board). We wish to use the nRF USB port. If possible, how do we route data transfer through the nRF USB port instead of the Interface MCU USB port?
  • Can you also confirm that the D+ and D- differential data lines (from the nRF SoC) are applicable for UART transfer?
• Can you please list all the communication lines between the interface MCU and the nRF SoC, and their respective purpose?
  • I have had a thorough read of the DK user guide as well as the nRF52833 product guide, but I can't seem to isolate all the data lines between the interface MCU and the nRF SoC. For example what is TxD and RxD for?
• A more general question, I see it is partially answered here, but is it possible to get a schematic and PCB review done through Nordic?

Thanks in advance! The amount of documentation already out there answered my initial bombardment of questions, which is testament to your incredible support! 

[Turbo J]

cheezballs said:

Are SWDIO and SWDCLK purely used for programming the SoC

SWD is intended for programming and debugging, but you can(ab)use it for data transfer using Segger RTT.

Note: The Segger EDU you linked can only be licensed for non-commercial use.

You can use the USB as a COM port using USB-CDC (example code in SDK) on a host PC. No, the D+ and D- are pure USB and NOT UART.

You cannot use the "interface" MCU in you custom design - as you don't have complete firmware (or license from SEGGER) for it.

The RxD and TxD can be used for an UART connection through the interface MCU into the PC host, using SEGGER drivers. This is intended for development and testing as it requires far fewer resources on the NRF chip compared to USB.

[cheezballs]

Thanks for your reply!

Turbo J said:

SWD is intended for programming and debugging, but you can(ab)use it for data transfer using Segger RTT.

This makes sense, thank you!

Turbo J said:

The RxD and TxD can be used for an UART connection through the interface MCU into the PC host, using SEGGER drivers. This is intended for development and testing as it requires far fewer resources on the NRF chip compared to USB

I see, thanks for that.

Turbo J said:

You can use the USB as a COM port using USB-CDC (example code in SDK)

Is this the same principle as the virtual COM port provided by the interface MCU? Could you please be more specific on what example shows this in the SDK? 

[Andreas]

Hi,

 

A more general question, I see it is partially answered here, but is it possible to get a schematic and PCB review done through Nordic?

This is possible, just upload your design as attachments to your message here. If you do not want other than Nordic engineers to see it you can create a 'private' ticket.

 

Best regards,

Andreas