Specifications

XT65/XT75 Hardware Interface Description
4.1 Operating Principles
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4.1.3 Supported Protocols
The GPS receiver supports three implemented protocols – NMEA, RTCM and UBX. It is able to recognize input
messages from any of these protocols (e.g., GGA, RMC GSA, GSV) and respond to them accordingly. Input
messages can be arbitrarily mixed.
Initially the NMEA protocol is enabled for outputs.
4.1.3.1 NMEA Protocol
The NMEA protocol is an industry standard protocol developed for marine electronics. It was originally designed
to allow data exchange between various sensors and navigation equipment aboard ships.
Nowadays, it is a de-facto standard for GPS receiver data output. For more information on the NMEA Standard
please refer to http://www.nmea.org.
4.1.3.2 UBX Binary Protocol
UBX is a proprietary protocol (developed by u-blox AG, Switzerland) used to transmit GPS data to a host com-
puter. The protocol has the following key features:
• Compact. 8 Bit binary data is used
• Checksum protected, using a low-overhead checksum algorithm
• Modular, using a 2-stage Message Identifier (Class- and Message ID)
UBX protocol offers a greater flexibility and more powerful messages than NMEA protocol.
It’s optimized to get the best performance and optimal debugging.
4.1.3.3 RTCM Protocol
The RTCM (Radio Technical Commission for Maritime Services) protocol is a unidirectional protocol (input to the
receiver) supplying the GPS receiver with real-time differential correction data (DGPS). The RTCM protocol
specification is available from http://www.rtcm.org. The GPS receiver supports the RTCM version 2.2 Correction
Type Messages 1, 2, 3 and 9.