This weather stations has a 0-5v serial output. I'm trying to read the serial output with the Adafruit 32u4 feather board and I get nonsense data out of it. When I hook the Ultimeter up to my serial->usb cable I get the normal data output. When I hook up the Ultimeter to a 5v arduino via SoftwareSerial in inverted mode I get proper data. But I need to connect this weather station to a 3.3v Feather board's hardware uart which doesn't seem to be able to operate in inverted mode. Is there a 5v -> 3.3 level converter that also will invert the serial signal ?
I think you're looking for an inverting amplifier. This can be done with either a BJT or a MOSFET (assuming your input is enough to turn the MOSFET on). Here's an example with a BJT:
The output range is independent of the input and is defined by the supply voltage.