I have built a custom board that is identical in schematic to the nRF52 DK board, with some additional circuitry connected as a SPI interface to the nRF chip. The MCU is the same Atmel SAM3U chip. That chip has its own rom-based software for booting, and when I plug in my board my PC recognizes the Atmel chip and loads a USB driver so it appears as a COM port. Using BOSSA I can see the board, and I can flash the Atmel SAM processor chip. I have tried flashing it with the most recent J-Link OB-SAM3U128-V2-NordicSemi 170213.bin file from the Nordic website, but when I do, the device will not longer plug-n-play and appear as a USB device. I can reset the ARM processor by erasing it and it again appears as a com port. I have tried changing the driver to J-Link CDC driver in order to see the device via windows, but have gotten stuck.
Can you explain what steps you follow when flashing the Atmel ARM chip (one off the shelf like I have) so that it eventually behaves like the MCU in the nRF52 DK? I assume that I have to load the J-Link.bin file and the MBED.bin files (from the Nordic site), but I am not sure what offsets I should use.
I appreciate your responses in advance.
