RE: Issue flashing custom boards and relationship crystal

Andreas — Fri, 26 Apr 2019 13:50:32 GMT

Hi,

Try soldering a 100nF on DEC1, incorrect decoupling here can make the onboard power supply unstable.

Best regards,

Andreas

RE: Issue flashing custom boards and relationship crystal

wpaul — Thu, 25 Apr 2019 18:11:22 GMT

When the chip powers up, it will be using the internal RC oscillator, and it will continue to do so until software running on the CPU switches over to a different clock source. This is true for both the 32MHz crystal for the high frequency clock and the 32.768KHz crystal for the low frequency clock.

This means that with a blank flash, the CPU must use the internal RC oscillator and the external crystals don't really matter.

A friend and I are working on a project with the nRF52840 and we followed the reference design of the nRF52840 DK with regards to the SWD pins, and it worked fine first time out of the box. We use the Olimex ARM-JTAG-USB-H debugger. The same debugger also works with the nRF52840 DK board. We used 10K pullup resistors on the SWDCLK, SWDIO and SWO pins.

-Bill