path: root/sfn.tex
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authorMatthias P. Braendli <matthias.braendli@mpb.li>2016-01-31 23:54:54 +0100
committerMatthias P. Braendli <matthias.braendli@mpb.li>2016-01-31 23:54:54 +0100
commit48c6128bc227e5bd7c5f09d4631cc502572c1dea (patch)
treeacd059b4a24e73b35aa451281e01b83eb604853e /sfn.tex
parentb0b8fbc61b3336bb29cd3cf83967f71f39958407 (diff)
Write some GPSDO text
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@@ -141,9 +141,45 @@ therefore rewrite the above equation as:
\sidenote{Explain relationship with ZeroMQ max buffer size}
-\subsection{Using Ettus GPSDO}
\subsection{Using ODR LEA-M8F GPSDO board}
+The ODR GPSDO board integrating a u-blox LEA-M8F module can be used as time and
+frequency reference for the USRP B200. \sidenote{TODO: Add Picture}
+The board design is available on the Opendigitalradio website, with
+a bill of materials describing how to source the components. The PCB itself can
+be manufactured in any PCB fab.
+The module includes the correct pin header so that it can be mounted directly
+onto the USRP B200, but also includes footprints for SMA connectors for other
+usages. Communication between the PC and the GPS is possible through USB or over
+UART through the B200.
+The u-blox LEA-M8F module is a GPS disciplined TCXO module, with a one-pulse per
+second and a reference clock output at a frequency of $30.72$ MHz. This is
+different than what the normal USRP firmware expects.
+Because the UART communication protocol and the reference clock frequency are
+different than for the GPSDO units Ettus supports, a modified version of UHD is
+necessary. This version includes new UHD sensors, used by ODR-DabMod to verify
+that the GPSDO is locked properly, and different configuration settings for the
+clock management PLL inside the USRP, making the USRP compatible to the
+$30.72$MHz reference clock frequency.
+The modified UHD version is available at
+\url{http://www.github.com/Opendigitalradio/uhd.git} and replaces Ettus' UHD.
+ODR-DabMod can be configured as follows:
+\subsection{Using Ettus GPSDO}
\sidenote{Give example}
% vim: spl=en spell tw=80 et