Current latest JLink firmware won't allow PPK working with DK RTT debugging.
The cause is the JLink chip on the DUT board won't put the SH_SWO/SH_SWCLK/SH_SWDIO in hi-Z mode when SH_VTG is grounded, which prevents the proper communication between the PPK and the external JLink.
Symptom would be:
- As soon as DUT JLink was connected (with JLinkExe), the external JLink would fail to communicate with PPK (Power Profiler Kit desktop application fails to connect).
- After releasing the DUT JLink (exit JLinkExe), the external JLink could talk to the PPK again.
I used the following JLink fw and neither would work:
- OB-SAM3U128-V2-NordicSemi compiled Jul 24 2017 17:30:12
- OB-SAM3U128-V2-NordicSemi compiled Nov 14 2016 16:58:29
Work-around would be use ribbon-cables (or flying wires) to bypass the SH-SWO pin (P19-6 on PPK, to P20-6 on PCA10040).
New DK's JLink firmware is needed to fix the issue.