Hi,
We are debugging a custom board running an nRF52840. For that, we are using nRF52840DKs, and we have a mix of v2.0.2 and v3.0.0. This is causing a headache, as we can't set it to work in v3.0.0 dev kits.
Our custom board has a 2x05 connector, were two of the unused pins (7 and 8) are used to break out a UART log for printing. Because the nRF52840 doesn't have the Vcom pins broken out, we use an intermediate PCB, an adapter board, to get a connection to the Vcom pins. So the chain is: custom board <-> adapter board <-> nRF5280DK as programmer
Here's the pinout of our setup
J1 is the pinout of the debug port of our custom board. J2 and J3 are the pinouts of the two headers on our adapter board. J4 and J5 show the pinout of the P19 port in the nRF52840DK in revisions v2.0.2 and v3.0.0 of the dev kit.
J1 (custom target board) is connected to J2 (adapter Board) with a ribbon. The adapter board powers the target, and we use it to access the Vcom. Then J3 on the adapter board is connected to J4/J5, depending on the revision of the dev kit
I've noticed that v2.0.2 used pin 9 as GND detect, which i think it's the mechanism used to detect an external target. That has seem to be removed from v3, and I can't find any references to it. On the other hand, pin 3 was connected to GND in v2.0.2 and to "SW0 select" in v3.0.0
What is "SW0 Select"? Again, a quick google search didn't reveal any results. We tried to short it to GND, and that way, our v3 DKs detect our target. If that pin is left floating, then rev3s can't see the external target, but rev2s can!
Should I just connect it to ground and call it a day?
Thanks!
