From a74919c2a89a6b1ae40b526c4ceadf1108bfd186 Mon Sep 17 00:00:00 2001 From: Martin Braun Date: Sun, 23 Mar 2014 15:11:26 +0100 Subject: docs: Moved manual to Doxygen --- host/docs/gpsdo.dox | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 host/docs/gpsdo.dox (limited to 'host/docs/gpsdo.dox') diff --git a/host/docs/gpsdo.dox b/host/docs/gpsdo.dox new file mode 100644 index 000000000..a67004acc --- /dev/null +++ b/host/docs/gpsdo.dox @@ -0,0 +1,81 @@ +/*! \page page_gpsdo Internal GPSDO Application Notes (USRP-N2x0/E1X0 Models) + +\tableofcontents + +This application note describes the use of integrated GPS-disciplined +oscillators (GPSDOs) for the USRP N-Series and E1xx. For information +regarding the GPSDO that is compatible with the USRP X-Series, please +see: \ref page_gpsdo_x3x0 + + +\section gpsdo_specs Specifications + +- **Receiver type**: 50 channel with WAAS, EGNOS, MSAS +- **10MHz ADEV**: 1e-11 over \> 24h +- **1PPS RMS jitter**: \< 50ns 1-sigma +- **Holdover**: \< 11us over 3h +- **Phase noise**: + - **1Hz:** -80 dBc/Hz + - **10Hz:** -110 dBc/Hz + - **100Hz:** -135 dBc/Hz + - **1kHz:** -145 dBc/Hz + - **10kHz:** \< -145 dBc/Hz + +Antenna Types: + +The GPSDO is capable of supplying a 3V for active GPS antennas or +supporting passive antennas. + +\section gpsdo_install Installation Instructions + +Instructions for mounting the GPSDO kit onto your USRP device can be +found here: http://www.ettus.com/content/files/gpsdo-kit_2.pdf + +\subsection gspdo_install_post Post-installation Task (N-Series only) + +Note: The following instructions are only necessary for UHD 3.4.\* +and below. + +This is necessary if you require absolute GPS time in your application +or need to communicate with the GPSDO to obtain location, satellite +info, etc. If you only require 10 MHz and PPS signals for reference or +MIMO use (see \ref page_sync), it is not necessary to perform this step. + +To configure the USRP to communicate with the GPSDO, use the +`usrp_burn_mb_eeprom` utility: + + cd /lib/uhd/utils + ./usrp_burn_mb_eeprom --args= --key=gpsdo --val=internal + + -- restore original setting -- + ./usrp_burn_mb_eeprom --args= --key=gpsdo --val=none + +\section gpsdo_use Using the GPSDO in Your Application + +By default, if a GPSDO is detected at startup, the USRP will be +configured to use it as a frequency and time reference. The internal +VITA timestamp will be initialized to the GPS time, and the internal +oscillator will be phase-locked to the 10 MHz GPSDO reference. If the +GPSDO is not locked to satellites, the VITA time will not be +initialized. + +GPS data is obtained through the **mboard_sensors** interface. To +retrieve the current GPS time, use the **gps_time** sensor: + +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp} + usrp->get_mboard_sensor("gps_time"); +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The returned value will be the current epoch time, in seconds since +January 1, 1970. This value is readily converted into human-readable +format using the **time.h** library in C, **boost::posix_time** in C++, +etc. + +Other information can be fetched as well. You can query the lock status +with the **gps_locked** sensor, as well as obtain raw NMEA sentences +using the **gps_gprmc**, and **gps_gpgga** sensors. Location +information can be parsed out of the **gps_gpgga** sensor by using **gpsd** +or another NMEA parser. + +*/ +// vim:ft=doxygen: -- cgit v1.2.3