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,

Are you using the  nrf52 DK or the nrf52840DK.? The tag you added confused me a bit.. Also, could you provide the link to the Arduino shield that you are using just to double check the pins..?

Regards,

Swathy

[hossein_m]

Hi,
I am using the NRF52840-DK ( pca10056). I will change the title; sorry for the confusion.

I am using the MAX3421e USB host shield, although I've modified it to work in only 3.3v. The pins are based on Arduino Uno, and the shield worked fine with the Arduino board.

https://5.imimg.com/data5/XK/RR/MY-1833510/usb-host-shield-for-arduino.pdf

https://github.com/felis/USB_Host_Shield_2.0

Also, I tried to use the SW10 to only use the external supply for the NRF, but even though there is a voltage on NRF52840's supply pins, it doesn't turn on. Do I have to make any more changes to the board?

Bests,

Hossein

[SwRa]

Hi Hussein,

In that case, you will see a  switch for nRF power source on the DK 

There are 3 options.. Li-Po, Vdd and theUSB.. Could you make sure that it is not set to USB? 

Regards,

Swathy

[hossein_m]

Hi,
The SW9 is on VDD. I mentioned in my first message that I didn't change any switch/jumper on the DK, and everything is on default mode.

Based on the DK's user guide I guess it should be solved using SW10, but I don't know why NRF stops working when SW10 is ON.

Bests,

Hossein

[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