Connecting jlink rtt causes the device to hang?

[wesson]

During the software testing process, our device is connected to the rtt viewer for testing. At present, a problem is found during the test: sometimes the test engineer suddenly finds that the rtt viewer has no log printed. At this time, other functions of the device are running normally, and then test The engineer clicks the connect option on the RTT Viewer again. After the RTT Viewer is connected, the device hangs up, no longer runs, and will not resume (the door dog is open). The device does not resume operation until the disconnect RTT Viewer is clicked. So far this phenomenon has appeared three or four times, please analyze it, thank you!
The following log is the connection log of RTT Viewer

LOG: Connecting to J-Link via USB...
LOG: Device "NRF52832_XXAA" selected.
LOG: InitTarget() start
LOG: InitTarget() end
LOG: Found SW-DP with ID 0x2BA01477
LOG: DPIDR: 0x2BA01477
LOG: Scanning AP map to find all available APs
LOG: AP[2]: Stopped AP scan as end of AP map has been reached
LOG: AP[0]: AHB-AP (IDR: 0x24770011)
LOG: AP[1]: JTAG-AP (IDR: 0x02880000)
LOG: Iterating through AP map to find AHB-AP to use
LOG: AP[0]: Core found
LOG: AP[0]: AHB-AP ROM base: 0xE00FF000
LOG: CPUID register: 0x410FC241. Implementer code: 0x41 (ARM)
LOG: Found Cortex-M4 r0p1, Little endian.
LOG: FPUnit: 6 code (BP) slots and 2 literal slots
LOG: CoreSight components:
LOG: ROMTbl[0] @ E00FF000
LOG: ROMTbl[0][0]: E000E000, CID: B105E00D, PID: 000BB00C SCS-M7
LOG: ROMTbl[0][1]: E0001000, CID: B105E00D, PID: 003BB002 DWT
LOG: ROMTbl[0][2]: E0002000, CID: B105E00D, PID: 002BB003 FPB
LOG: ROMTbl[0][3]: E0000000, CID: B105E00D, PID: 003BB001 ITM
LOG: ROMTbl[0][4]: E0040000, CID: B105900D, PID: 000BB9A1 TPIU
LOG: ROMTbl[0][5]: E0041000, CID: B105900D, PID: 000BB925 ETM
LOG: RTT Viewer connected.
LOG: All Terminals tab cleared.
LOG: Connecting to J-Link via USB...
LOG: Device "NRF52832_XXAA" selected.
LOG: InitTarget() start
LOG: InitTarget() end
LOG: Found SW-DP with ID 0x2BA01477
LOG: Failed to power up DAP
LOG: InitTarget() start
LOG: InitTarget() end
LOG: Found SW-DP with ID 0x2BA01477
LOG: DPIDR: 0x2BA01477
LOG: Scanning AP map to find all available APs
LOG: AP[2]: Stopped AP scan as end of AP map has been reached
LOG: AP[0]: AHB-AP (IDR: 0x24770011)
LOG: AP[1]: JTAG-AP (IDR: 0x02880000)
LOG: Iterating through AP map to find AHB-AP to use
LOG: AP[0]: Core found
LOG: AP[0]: AHB-AP ROM base: 0xE00FF000
LOG: CPUID register: 0x410FC241. Implementer code: 0x41 (ARM)
LOG: Found Cortex-M4 r0p1, Little endian.
LOG: FPUnit: 6 code (BP) slots and 2 literal slots
LOG: CoreSight components:
LOG: ROMTbl[0] @ E00FF000
LOG: ROMTbl[0][2]: 3A1AF000, CID: 01000000, PID: EFCAF588 ???
LOG: RTT Viewer connected.

[Simonr]

Hi

1. And how is the J-Link debugger connected to your custom board. I assume using the SWD pins, VDD and GND? And what voltage is the custom board provided with and what does it 

2. Does the application do something else than print logging information to tell you it's running? Any BLE activity or LEDs/GPIOs that should be toggling that you can check if are running?

4. Can you try updating your J-Link version to at least 7.66a, as there have been some fixes/patches since then (if your J-Link debugger supports it of course).

Best regards,

Simon