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Diffstat (limited to 'host')
| -rw-r--r-- | host/docs/sync.dox | 3 | ||||
| -rw-r--r-- | host/docs/usrp_n3xx.dox | 22 |
2 files changed, 24 insertions, 1 deletions
diff --git a/host/docs/sync.dox b/host/docs/sync.dox index 9ce618010..9174bf5de 100644 --- a/host/docs/sync.dox +++ b/host/docs/sync.dox @@ -17,7 +17,8 @@ USRP devices take two reference signals in order to synchronize clocks and time: - A 10 MHz reference to provide a single frequency reference for all - devices. + devices (in some devices, other reference frequencies than 10 MHz are + also supported). - A pulse-per-second (PPS) to synchronize the sample time across devices. diff --git a/host/docs/usrp_n3xx.dox b/host/docs/usrp_n3xx.dox index 21b156296..4524a2e03 100644 --- a/host/docs/usrp_n3xx.dox +++ b/host/docs/usrp_n3xx.dox @@ -671,6 +671,28 @@ will look like this: \section n3xx_synchronization Clock/Time Synchronization +\subsection n3xx_synchronization_overview Overview + +To choose a source for clock (frequency) and PPS (time), use the `clock_source` +and `time_source` device arguments just like with any other USRP (see also +\ref page_sync). The following combinations are supported: + +`clock_source` | `time_source` | Notes +----------------|----------------|--------------------------------------------- +`internal` | `internal` | Default value +`external` | `internal` | The PPS will be generated from the reference signal, but this does not allow time synchronization between devices. +`external` | `external` | The device assumes that the external reference clock and PPS are synchronized. +`gpsdo` | `gpsdo` | This will work even without GPS reception (see below). + +The combination of `clock_source=external,time_source=gpsdo` is not available +out of the box, but can be enabled by patching the MPM source code (n3xx.py). +This is considered an advanced and unsupported use case. Read the appropriate +source code for a description of drawbacks. Using this mode will cause unreliable +phase alignment. + +See the following sections for more details on the individual synchronization +options. + \subsection n3xx_synchronization_internal Internal references The N3xx series has an onboard GPSDO as well as a 25 MHz reference oscillator, |