I appreciate a number of things about this unit. The onboard regulator that allows it to be run from 5 volts or 3.3 is nice. The availability of a connector for an external antenna. The large easily replaceable battery. And last of all, Adafruit supplied the breakaway header. Thanks.
Vin should be power to this unit, from 3.3 to 5 volts.
3.3 is regulated power out, up to 100 mA is available.
Vbat is an alternate way to hook up a battery if you don't want
to install a coin cell. I won't use this.
EN is an enable, it is pulled up so the unit will run, you can pull
it down if you want to power it down.
Fix is the same as the red LED. It pulses at 1 Hz if there is no fix.
When you have a fix, it will pulse high for 200 ms every 15 seconds.
Not terribly useful for a microcontroller.
PPS pulses high for 50-100 ms every second at 3.3 volts.
It took about a minute to get a fix the first time. After that it seems essentially instantaneous.
Amazingly, it does not lose the fix when I bring it inside my metal roofed workshop. And if I unplug it, then get it started again inside my workshop, it gets a fix in about 5 seconds. This makes it a much better performer than the inexpensive Ublox NEO-6M units I have, which is not terribly surprising.
I also have a Sparkfun SAM-M8Q, which is based on the Ublox M8. I claims similar sensitivity and also gets lock in 5 seconds or so inside my workshop.
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