If you've been following any of my other GPS project you'll know that the Venus838LPx-T is being EOLed. SkyTraq's replacement is the PX1100T, which has a number of improvements. It does, however, necessitate both hardware and firmware changes.

On the hardware side, there are fewer parts required. The module itself injects 3.3 volt active antenna power, so there's no longer a need for an external bias-T. It's also a castellated edge board style module rather than an LGA-69 package (which is a lot easier for me to deal with).

On the software side, the serial baud rate is 115200 rather than 9600, and some of the messages are in the form $GNxxx rather than $GPxxx, which reflects the quad constellation support.

One disadvantage is that there is no FIX LED output pin, so for backwards compatibility I've implemented the equivalent behavior (on for bad GPS, blinking at 1/2 Hz for good) on one of the controller pins. You could argue that it's redundant, given that one of the debug pins is simply on for bad and off for good GPS. The benefit to it before was that it was from the receiver module itself, and thus independent of the controller.