Architecture extension; handle variable sample rates.

1 files changed, 19 insertions, 6 deletions

diff --git a/gpsd.xml b/gpsd.xml
index 1c5fd237..5cea0bed 100644
--- a/gpsd.xml
+++ b/gpsd.xml
@@ -190,12 +190,25 @@ continue to communicate at the old speed.</para></listitem>
 
 <varlistentry>
 <term>c</term>
-<listitem><para>Returns, as "C=%d", the cycle time of updates in
-seconds. This command will return '?' at start of session, before the
-first full packet has been received from the GPS, because its type is
-not yet known. To set up conditions for a real answer, issue it
-after some command that reads position/velocity/time information
-from the device.</para></listitem>
+<listitem>
+<para>If the driver has the capability to change sampling
+rate the command "C=%f" does so, setting a new cycle time
+in seconds.</para>
+
+<para>If the driver has the capability to change sampling rate, this
+command always returns "C=%f %f" giving the current cycle time in
+seconds and the minimum possible cycle time at the current baud rate.
+If the driver does not have the capability to change sampling rate,
+this returns, as "C=%f", the cycle time in seconds only.</para>
+
+<para>Either number may be fractional, indicating a GPS cycle shorter
+than a second; however, if >1 cycle time must be a whole number. This
+command will return '?' at start of session, before the first full
+packet has been received from the GPS, because its type is not yet
+known. To set up conditions for a real answer, issue it after some
+command that reads position/velocity/time information from the
+device.</para></listitem>
+
 </varlistentry>
 
 <varlistentry>