Programming external MCU with nRF5340 DK

[mm784]

Hello

I want to clarify something because there seems to be a lot of conflicting information on Dev Zone, and the nRF5340 DK documentation doesn't specify the following:

Can the DK be used to program external boards with VDD other than 3.0V? I understand that 3V is the default when DK is powered by USB, but the VDD of my external boards is not 3V.

Some mention that it is not possible without the use of level shifters
 Programming using P19 external nrf5340 board powered at 1.8V 

Others say it is possible. To do that, the solder bridge SB19 on the nRF5340 DK must be shorted, so that the VDD of the external board is used as VIO_REF for debugging. 

  nRF5340-DK custom board flashing 1.8V 

 I can't program external board with nRF5340 2.0.2 

The board I have with nRF5340 SoC is battery powered and can have a VDD ranging from 3V to 1.8V. 

Can I short SB19 on the nRF5340 DK and have my external board supply VIO_REF to P19 for debugging?

[Charlie]

Hi,

Yes, you can, but make sure you nRF5340DK has same debug output circuit design as following.

 RE: I can't program external board with nRF5340 2.0.2 

You can find your nRF5340DK schematic here: www.nordicsemi.com/.../Download

Best regards,

Charlie

[mm784]

Hi Charlie,

Thank you for confirming. 

I have 2 boards, one is battery powered, and the other one is USB powered. Can you also confirm the following. 

1.  On the board which is battery powered, the VDD_nRF can fluctuate depending on battery state, from 3V to 2.5V and lower. The information you shared indicates that for debugging this board, the SB 19 must be shorted so that the reference voltage of the debugger on the DK is always the same as the VDD of the SoC on my external board. 

2. On the board that is USB powered, VDDH is 5V. The default output of the internal high voltage regulator VREGH is 1.8V. Does it mean that even for programming this external SoC that is powered by 5V on VDDH, the SB19 must still be shorted, because by default the VDD_nRF and its I/O voltage level will be 1.8V. 

Thank you

[Charlie]

Hi,

The programming and debugging should work as long as the GPIO voltage is matched between JLink-OB chip and your target chip.

You can test and monitor with a multimeter when you are programing.

regards,

Charlie