Error programming external nRF52 with Dev Kit: Could not fetch memory size of target devkit: Error: Error occured when get library info. Errorcode: CouldNotOpenDevice (0x4) Lowlevel error: Unknown value (ffffff24)

[Noelle]

I'm trying to program an nRF52 on a custom PCB using the nRF52-DK and am getting an error when connecting with nRF Connect v3.6.1.

I made the following connections from the P0.19 "Debug Out" header of my nRF52-DK to my PCB according to the guidelines.

DK Debug Out	Custom PCB
VTG	3.3V
GND_DETECT GND	GND
SWDIO	SWDIO
SWDCLK	SWDCLK
SWO	P0.18/TRACEDATA[0]/SWO
RESET	RESET

The device appears in the list of available connections in nRF Connect as PCA10040 through a serial port, but gives the following error when selected:

Could not fetch memory size of target devkit: Error: Error occured when get library info. Errorcode: CouldNotOpenDevice (0x4) Lowlevel error: Unknown value (ffffff24)

I've confirmed power on the PCB is 3.3V and checked the programming header connections, so I'm not sure what could be the issue. Thanks in advance for any help.

[hmolesworth]

Note the VTG pin is a voltage sense line (VDD Detect), not a supply line. The custom PCB requires a VDD supply, which can be taken from P20 VDD on the PCA10040 DK board.

I should probably add that in the absence of the VDD supply to the external PCB the digital pins will phantom power (backdrive) the PCB via the internal schottky protection diodes which means you might measure a voltage on the PCB but it will be of insufficient power to allow programming the PCB.

[Noelle]

I'm not using the DK to power the PCB - I have an external power supply and a 3.3V voltage regulator onboard.

[hmolesworth]

Ah, in that case I would suggest doing an unconditional flash erase all, particularly if the PCB is using a module which may have protections set. If that doesn't help it's almost time for the Nordic team to be on line :-)