I'm having problems with debugging LPC4333. We followed all design notes when layouting our board. But it's already 5-th MCU that I can't debug. We use SWD for debugging.
We've put resistors 100R in serial to avoid possible short circuit and protection diodes on all IOs (ESD) to limit the voltage in parallel.
Right now I have a LPC4333 on our board, that I've programmed yesterday, and it worked. Today it doesn't. The firmware runs and does it's job, the only problem is, I can't program it. If I setup the boot pins to start internal bootloader and load the firmware over FlashMagic it also works. Just SWD is down.
I have another board with the same MCU that I can program over and over again, the SWD interface works fine on it.
No debug pins are configured in the firmware, they're left at their default states. DBGEN is left unconnected, due to its internal 50k pull up being enough to enable SWD.
Could someone please give any tip of what can go wrong?