SparkFun GPS-RTK-SMA Breakout-ZED-F9P (Qwiic)-Voltage:5V or 3.3V Logic:3.3V | Concurrent reception of GPS GLONASS Galileo BeiDou High precision GPS 10mm 3 dimensional accuracy Receives L1C/A & L2C bands

Very good capture performance and lock-time. Good for serious applications.

Spent a week trying the differing and dispersed documentation suggestions that I could find on the web and support forums, but ultimately established that no matter what i tweaked, cut, or downloaded, the I2C bus would eventually crash either during boot, setup, or a few GPS readings. And it stays down. Need to ground the reset pin or pull pwr, and then reboot & try setup cmds again, being ready to do it over and over again. Makes for a complicated system, as extra components are necessary, and consuming additional power. Unfortunately had done a lot of prep work anticipating that the I2C & qwiic connectors would do their job with an arduino. So far, can only use the GPS manually with the excellent U-center utility on a larger computer with usb. support. Searched for more complete and consistent specs and examples for wiring & commanding the other comm channels. None of the examples worked with my Arduinos. over the Qwicc connector I2C bus. Its the only I2C link that I've had any trouble with in 10 years. At some point, the device pulls one of the I2C lines low, blocking all comms until reset or pwr cycle. Update: Was eventually able to by lengthy experiments & watching a scope, create code that worked in ublox mode, and was stable for hours over the I2C bus. Limited success but at least with difficulty, it can be made to work with the newer faster Arduinos.