I am trying to create a hobby project with this gas sensor:
Since it will be running from battery (tiny lipo - 350mAh, via a PowerBoost 500 Basic), I really care about power usage.
The gas sensor needs a 5V input, which I am planning on supplying from the VIN pin on the photon.
For the photon, I have two options for powering it:
1.) power it via the VIN pin directly (with a breadboard - so I can use the same power “rail” to power the gas sensor)
2.) power it via micro USB port (and use the VIN pin to power the gas sensor directly)
The part I am having a hard time understanding/picturing is this for the gas sensor:
You can use the EN pin to power it off (pull it high to 5V to turn off).
If I am understanding @peekay123’s comment (here: 3.3 out on one pin, in on another... anything I need? ):
 FT = 5.0V tolerant pins. All pins except A3 and DAC are 5V tolerant (when not in analog mode). If used as a 5V input the pull-up/pull-down resistor must be disabled.
Does that mean that as long as I am not using the 5V (VIN) pin as an input (I do need to use it as an OUTPUT to power the gas sensor), it’s OK to set a Digital pin (let’s say D1 as an example) as “INPUT_PULLUP”?
If not - how can I achieve this?
EDIT1: Attaching fritz (NOTE: yellow wire is what I am curious about)