Hi all,
I’ve noticed that with my Photons (and my Spark Core) that D7 powers on (dimly) momentarily when new code is flashed onto the device. I couldn’t find anything about this elsewhere - is there a way that this can be disabled? I haven’t checked any of the other pins but if need be I can rewire one of my circuits to another pin if this is the only fix.
It’s a bit of a pain as I’m using D7 to control the power of a device which always shuts it down when new code is flashed!
Thanks!
When new code is flashed and the Photon “reboots” the pins are in a High impedance state and you will notice this behavior in microcontrollers in general.
You should consider re-designing the circuit if you need the power to be on all the time regardless of the GPIO state 
Cool thanks. Yeah bit tricky to redesign the circuit - not a huge deal. It’s not every day that I flash it so I can live with it. Cheers!
I’d agree with the need to rewire, if this behaviour causes problems, but you might need to check which pins you actually can use, since others do behave similar but don’t show via LED.
I think the dim blue LED actually comes from the pull-up resistor being attached on bootup on some of the JTAG pins.
So not all pins will be high impedance on bootup.
Cool - thanks for the feedback! I’ll see what I can do with the circuit. Cheers.