Just in case someone wants to alter the GPS update rate on a Adafruit Ultimate GPS Logger Shield. This may come in handy if you want to reduce the power consumption of your board. According to a datasheet of the GPS-chip the max update rate is 10000ms/10sec. So how do you set it?

Relatively simple: go to your Adafruit_GPS-library, open Adafruit_GPS.h and look for these lines:

#define PMTK_SET_NMEA_UPDATE_1HZ "$PMTK220,1000*1F"
#define PMTK_SET_NMEA_UPDATE_5HZ "$PMTK220,200*2C"
#define PMTK_SET_NMEA_UPDATE_10HZ "$PMTK220,100*2F"

So this will define the name of the method/function/whatever which will be called in your Arduino-sketch, e.g. _PMTK_SET_NMEA_UPDATE1HZ. PMTK220 is the chip-internal code for update rate. So we say: Hey, I want to alter the update rate. The value after the comma is the update rate in milliseconds. We set it to 10000 (or whatever you like). The value behind the is the checksum which the chip requires. Thanks to Stevens post about reading GPS data with bash I stumpled upon the MTK NMEA checksum calculator. So you put in PMTK220,10000 and get back _$PMTK220,100002F_. That’s it. Our new line would read:

#define PMTK_SET_NMEA_UPDATE_10SEC  "$PMTK220,10000*2F"

Just set PMTK_SET_NMEA_UPDATE_10SEC in your sketch and upload it.