diff options
| -rw-r--r-- | host/docs/CMakeLists.txt | 1 | ||||
| -rw-r--r-- | host/docs/gpsdo.rst | 2 | ||||
| -rw-r--r-- | host/docs/gpsdo_b2x0.rst | 80 | ||||
| -rw-r--r-- | host/docs/index.rst | 3 |
4 files changed, 84 insertions, 2 deletions
diff --git a/host/docs/CMakeLists.txt b/host/docs/CMakeLists.txt index 17744db7d..fa6e98918 100644 --- a/host/docs/CMakeLists.txt +++ b/host/docs/CMakeLists.txt @@ -26,6 +26,7 @@ SET(manual_sources coding.rst dboards.rst gpsdo.rst + gpsdo_b2x0.rst general.rst images.rst stream.rst diff --git a/host/docs/gpsdo.rst b/host/docs/gpsdo.rst index 1e9019a0f..1cf1dae29 100644 --- a/host/docs/gpsdo.rst +++ b/host/docs/gpsdo.rst @@ -1,5 +1,5 @@ ======================================================================== -UHD - Internal GPSDO Application Notes +UHD - Internal GPSDO Application Notes (USRP-N2x0/E1X0 Models) ======================================================================== .. contents:: Table of Contents diff --git a/host/docs/gpsdo_b2x0.rst b/host/docs/gpsdo_b2x0.rst new file mode 100644 index 000000000..bca10e99a --- /dev/null +++ b/host/docs/gpsdo_b2x0.rst @@ -0,0 +1,80 @@ +======================================================================== +UHD - Internal GPSDO Application Notes (USRP-B2X0 Models) +======================================================================== + +.. contents:: Table of Contents + +This application note describes the use of integrated GPS-disciplined +oscillators with Ettus Research USRP devices. It pertains specifically +to the Jackson Labs LC_XO device unless noted otherwise. + +------------------------------------------------------------------------ +Specifications +------------------------------------------------------------------------ +* **Receiver type**: 50 channel with WAAS, EGNOS, MSAS +* **10MHz ADEV**: 5e-11 over >24h +* **1PPS RMS jitter**: <50ns 1-sigma +* **Holdover**: <20us over 3h + +**Phase noise**: + ++------------+-------------+------------+ +| | TCXO | OXCO | ++============+=============+============+ +| **1Hz** | -65dBc/Hz | -75dBc/Hz | ++------------+-------------+------------+ +| **10Hz** | -102dBc/Hz | -110dBc/Hz | ++------------+-------------+------------+ +| **100Hz** | -132dBc/Hz | -132dBc/Hz | ++------------+-------------+------------+ +| **1kHz** | -148dBc/Hz | -142dBc/Hz | ++------------+-------------+------------+ +| **10kHz** | -152dBc/Hz | -145dBc/Hz | ++------------+-------------+------------+ +| **100kHz** | <-155dBc/Hz | -150dBc/Hz | ++------------+-------------+------------+ + +**Antenna Types:** + +The GPSDO is capable of supplying a 3V for active GPS antennas or supporting passive antennas. + +------------------------------------------------------------------------ +Installation Instructions +------------------------------------------------------------------------ +To install the GPSDO, you must insert it into the slot on the board +near the 10 MHz Reference SMA. Keep in mind that the two sides of the +GPSDO have a different number of pins. When inserting the GPSDO, make +sure to press down firmly and evenly. When turning on the USRP B2X0 device, +a green LED should illuminate on the GPSDO. This signifies that the unit +has successfully been placed. + +**NOTE: The pins on the GPSDO are very fragile. Be sure to press down +evenly, or the pins may bend or break. Once the GPSDO is in place, +we very highly discourage further removal, as this also risks damaging +the pins.** + +------------------------------------------------------------------------ +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 10MHz 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: + +:: + + 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. diff --git a/host/docs/index.rst b/host/docs/index.rst index 27523c139..65069059f 100644 --- a/host/docs/index.rst +++ b/host/docs/index.rst @@ -32,7 +32,8 @@ Application Notes * `Daughterboard Application Notes <./dboards.html>`_ * `Transport Application Notes <./transport.html>`_ * `Synchronization Application Notes <./sync.html>`_ -* `Internal GPSDO Application Notes <./gpsdo.html>`_ +* `Internal GPSDO Application Notes (USRP-N2X0/E1X0 Models) <./gpsdo.html>`_ +* `Internal GPSDO Application Notes (USRP-B2X0 Models) <./gpsdo_b2x0.html>`_ * `Calibration Application Notes <./calibration.html>`_ ^^^^^^^^^^^^^^^^^^^^^ |