General comments: I have the GS406 and have made a breakout board for it. This GPS module works well. The connector seems fragile.
Question: Pin 9 on the connector says NC but is shown as GPIO1. I noticed that it goes to R3 that is not populated on the circuit board. I have attempted to see if this footprint is connected to any pins on the actual ublox module using a meter, but it does not seem to be. I would like to hook up an LED to see when the unit has a lock (similar to how the GS405 works). Any ideas on how to do this? Any ideas what the purpose of the unpopulated R3 actually is?
Also, has anyone upgraded the firmware on these modules?
Update: I upgraded the firmware myself using u-center and the serial connection. It took a while (15 mins or so) but it was very simple.