I’m having a strange problem with a Photon that I’m attempting to use with an external USB power supply, through a charging circuit using a MAX1555.
When powered via USB directly to the Photon, it runs just fine and connects to the WiFi. If I instead power it through my circuit, it powers on to solid white.
Testing the voltage to VIN when on my external supply I get 4.17V, which should be in spec. The 3.3V out shows 3.3V, as it does when using on-board USB power. The only difference I see is that when using on-board USB, I see 5V on VIN (which makes sense directly from USB). My understanding is that anything between 3.6V to 5.5V should work.
There isn’t anything else connected to the Photon at this point, just power.
When in this solid white mode, the setup and reset buttons sort of work. I can get it into DFU mode (flashing yellow), but not WiFi setup mode.
Has anyone experienced this? Thanks!