I have made a custom PCB to test Particle P1. Its a two layer board made in Eagle CAD.
The data sheet of P1 doesn’t give any specific instructions on Making the PCB, heat dissipation of P1 or any related information. But I went ahead with my custom PCB following similar design of Sparkfun Redboard with some of my additional components.
I am attaching the board layout and schematic here;
Nice design! Could you measure the current input to VBUS, or when applying 5V to VCC? The LM1117 might not be warm because it has a low dropout voltage and has protection. It seems like there may be some internal short inside the P1. This could be the cause of ESD or wrong reflow soldering profile (too high or too long). Where did you source your BM-14 from? I noticed it doesn’t have the Particle part number/logo or P1 on it. If you have more of these modules, maybe pre-check the power rails for shorts before soldering onto the PCB. Then check after soldering. You can also remove this BM-14’s can with hot air and look for parts that have shifted around during reflow, or even potentially find the bad component (that would be amazing). And finally you can try removing the BM-14 and see if the power rails are shorted once removed.
From the picture the board seems well manufactured. Did you do a close inspection of the board? Also of the soldered board? I.e., no stray solder balls lingering around? The only thing I don’t like is the way the 3.3V is distributed across the board - why not use a power plane? I don’t have a a very good feeling when I see feebly traces for power. Though I would not suggest that this is your problem now, it could be in the future. I have seen some nice oscillations on boards like these when 3.3 is not sturdily distributed and those power swings rip your part up real quick.
If you did not source it from Particle then I’m pretty sure the Particle bootloader & firmware is not loaded on it. Somebody else will need to confirm that though, I may be wrong about this assumption.