debugging while using external supply on NRF52840-DK

[hossein_m]

Hi Nordic,

I want to use an Arduino USB host shield with NRF52840-DK. Since the VDD on DK is 2.5v and MAX3421 on the shield works with 3 to 3.6 volts, I have to use an external supply to power both boards.

Everything seems to work fine. However, when I try to connect the DK's J2 USB to debug my project, the VDD voltage decreases to about 2.5 volts, which shuts down the host shield.

Is there any other way than using an external debugger to stop the VDD voltage from decreasing?

BTW I didn't change any switch/jumper on the DK, and everything is on default mode.

[SwRa]

Hi Hossein,

The device should not stop working when SW10 is ON.. Could you tell me how you made the connections ? Did you connect the external power supply to P21 or P22.? Take a look at the set up mentioned here: https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/direct_supply.html?cp=4_0_4_7_2_4

Also, which USB port did you use to connect the USB (J2 or J3).? It would be better if you could share a photo of your set up..

Regards,

Swathy

[hossein_m]

Hi Swathy,

Sorry for the late response.
- A photo of my setup:

- I use the J2 USB port to debug my project and connect the external power source to P21.

- To test whether the board works with an external supply, I wrote a simple code to toggle one of the pins on the board ( one that has no connection with any peripherals on the board). This code worked fine when SW10 was off but didn't work when it was on.

If there are any other switches or options related to this problem, please let me know to check them too so we can reach a solution.

Bests,

Hossein