Photon Breathing white LED after mounting to custom PCB

I am newbie to the Photon and the programming game in general. I just soldered a good Photon to a custom PCB (unfortunately without a socket and upon applying power, the device flashes white and never gets past white). When I disconnect power and connect my USB, it will initialize for a 10 seconds or less and start breathing white again. Over time the white flashing starts to speed up. I did notice a proper initialization when I thoroughly scrubbed the board of all the flux residue but it only lasted for maybe 30 more seconds and back to white.

Here are some other relevant facts:

  • I do not have anything connected to the RST pin.
  • The D7 LED is very dim and flashes with the white light.
  • The 5VDC source is regulated through the following voltage sources 115VAC -> 24VDC -> 12VDC -> 5VDC.
  • I have noticed that when the 3V3 pin and the RST pin are displayed on an oscilloscope that they look identical. The pins are not shorted on the PCB. And none of the other inputs look like they have anything displayed abnormally on them.

According to the forums it sounds like the board is in a constant reset condition. Can anyone explain what may have caused this or what else I may need to check before I plug in another board? Any help would be much appreciated.

Are you able to place the device in DFU mode?

Negative, it will not stop flashing white long enough to go into another mode.

I wonder what mode it is in… Can you share more about what’s connected to the Photon?

Can you press on the SETUP button and plug in the USB power to see if it enters DFU mode?

There were no peripheral devices connect except for 5VDC, Ground, resistors, solder runs, and empty IC sockets. I was just testing the board with the power supply when it happened.

I tried to press the SETUP button and connect the USB with no avail. When I press either the setup or reset button all the lights go out but the blue D7 light still flashes very dimly at the same rate as the white LED would. None of the lights come on until I let go of the buttons. Then back to flashing white.

Interesting. Is it convenient for us to view the design of the PCB?

1 Like