.cycle_chars is gone, replaced by min_cycle.

2 files changed, 10 insertions, 57 deletions

diff --git a/www/hacking.html b/www/hacking.html
index ffac068e..9ee7f89b 100644
--- a/www/hacking.html
+++ b/www/hacking.html
@@ -105,7 +105,6 @@ file in the source distribution.</p>
 <li><a href="#reports">Where to put the data you get from the GPS</a></li>
 <li><a href="#confidence">Report errors with a 95% confidence interval</a></li>
 <li><a href="#logfiles">Log files for regression testing</a></li>
-<li><a href="#throughput">Throughput computation for baud rate changes</a></li>
 </ol>
 <li><a href="#buffering">The buffering problem</a></li>
 <ol>
@@ -995,7 +994,7 @@ the null-terminated array in drivers.c.</p>
 it should live in its own C source file named after the driver type.
 Add it to the libgps_c_sources name list in Makefile.am</p>
 
-<p>The easiest way write a driver is probably to copy the driver_proto.c
+<p>The easiest way to write a driver is probably to copy the driver_proto.c
 file in the source distribution, change names appropriately, and write
 the guts of the analyzer and writer functions.  Look in gpsutils.c
 before you do; driver helper functions live there.  Also read some
@@ -1005,7 +1004,7 @@ existing drivers for clues.</p>
 On Writing A GPSD Driver.</a></para>
 
 <p>There's a second kind of driver architecture for
-<code>gpsmon</code>, the real-timr packet monitor and diagnostic tool.
+<code>gpsmon</code>, the real-time packet monitor and diagnostic tool.
 It works from monitor-object definitions that include a pointer to the
 device driver for the GPS type you want to monitor.  See
 monitor_proto.c for a prototype and technical details.</p>
@@ -1151,36 +1150,6 @@ logfile format.</p>
 portion during which the GPS has no fix, a portion during which it has
 a fix but is stationary, and a portion during which it is moving.</p>
 
-<h3 id="throughput">Throughput computation for baud rate changes</h3>
-
-<p>At low baud rates it is possible to try to push more characters of
-NMEA through per cycle than the time to transmit will allow.  Here
-are the maxima to use for computation:</p>
-
-<div>&nbsp;</div>
-
-<table border='1'>
-<tr><td>ZDA       </td><td>36</td></tr>
-<tr><td>GLL       </td><td>47</td></tr>
-<tr><td>GGA       </td><td>82</td></tr>
-<tr><td>VTG       </td><td>46</td></tr>
-<tr><td>RMC       </td><td>77</td></tr>
-<tr><td>GSA       </td><td>67</td></tr>
-<tr><td>GSV       </td><td>60 (per line, thus 180 for a set of 3)</td></tr>
-</table>
-
-<p>The transmit time for a cycle (which must be less than 1 second)
-is the total character count multiplied by 10 and divided by the 
-baud rate.</p>
-
-<p>A typical budget is GGA, RMC, GSA, 3*GSV = 82+75+67+(3*60) = 404.</p>
-
-<p>When you write a driver that includes the capability to change
-sampling rates, you must fill in the cycle_chars member with 
-a maximum character length so the daemon framework code will
-be able to compute when a sample-rate change will work.  If
-you have to estimate this number, err on the high side.</p>
-
 <h1 id="buffering">The buffering problem</h1>
 
 <p>Considered in the abstract, the cleanest thing for a
diff --git a/www/writing-a-driver.xml b/www/writing-a-driver.xml
index 6b6c673b..13834893 100644
--- a/www/writing-a-driver.xml
+++ b/www/writing-a-driver.xml
@@ -616,10 +616,9 @@ write of the data, which is provided by the default routine
 <function>pass_rtcm</function>. If the device does not
 accept differential data, the value is NULL.</para>
 
-<!-- modified by ESR, 2009 -->
 <para><structfield>.speed_switcher</structfield> points to a block of
 code to change baud rate, parity, and stop bits (if supported). If
-your ddevice can support some speed/parity/stopbits combinations but
+your device can support some speed/parity/stopbits combinations but
 not others, it should return false on a mode-change request it can't
 handle.</para>
 
@@ -629,7 +628,10 @@ binary mode (1).</para>
 
 <para><structfield>.rate_switcher</structfield> points to a block of code
 to change the maximum number of fixes your device can generate
-in 1 second.</para>
+in 1 second. If this method is present, you should also fill in 
+<structfield>.min_cycle</structfield> tio indicate the device's 
+minimum cycle time in seconds; a 0 value indicates that it is limited
+only by yjr data throughput of the reporting channel.</para>
 
 <para><structfield>.control_send</structfield> points to a block of
 code that can take a buffer full of message payload, wrap iit in
@@ -643,11 +645,12 @@ possible, assemble your packet in
 <structfield>session->msgbuflen</structfield>; this will allow 
 gpsmon to display the control messages it sends for you.</para>
 
-<para><structfield>.cycle_chars</structfield> is explained in
+<!-- deleted by ESR, 2009 -->
+<!-- <para><structfield>.cycle_chars</structfield> is explained in
 <quote>Throughput computation for baud rate changes</quote> in the
 <quote>Hacker's Guide to GPSD</quote> in the general
 documentation. It's only necessary to fill this in if you have
-<structfield>.rate_switcher</structfield> capability</para>
+<structfield>.rate_switcher</structfield> capability</para> -->
 
 <para><structfield>.revert</structfield> points to a block of
 code that is conditionally run each time the device is closed if
@@ -666,25 +669,6 @@ which is run unconditionally each time the device is to be closed.
 <quote><option>-n</option> </quote> switch is not active.) This is
 also where you should undo any port parameter changes you made in
 <structfield>.probe_detect</structfield>above.</para>
-
-<!-- deleted by ESR, 2009 -->
-<!-- <para><structfield>.cycle</structfield> is a number giving the number of
-fixes per second you can get. Gets updated if you can rate-switch
-and user gives a <application>gpsd</application> 'C' command.</para> -->
-
-<!-- modified by ESR, 2009 -->
-<para>The connection between some of the above was confirmed with Eric
-Raymond as follows.</para> <para>The inter-relationship between
-<structfield>.speed_switcher</structfield>,
-<structfield>.rate_switcher</structfield>,
-<structfield>.cycle_chars</structfield> is:-</para> <para>If we can change
-baud rate (<structfield>.speed_switcher</structfield>) and we can
-alter the rate at which fixes are delivered
-(<structfield>.rate_switcher</structfield>), then we need to know the
-number of characters in a fix string
-(<structfield>.cycle_chars</structfield>) so that we can compute the
-minimum reporting cycle time we can ask
-for.</para>
 </sect1>
 
 <sect1><title>Details of the driver parser</title>