doc/other.xml: More fiddling about.
More documentation tidy-ups. I'll probably get bored eventually!
This commit is contained in:
Ian Abbott
parent
708b802811
commit
c1a454bb40
1 changed files with 147 additions and 106 deletions
253
doc/other.xml
253
doc/other.xml
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@ -56,19 +56,20 @@ digital subdevices on a particular board.
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<para>
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Individual bits on a digital I/O device can be read and written using
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the functions
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the functions <link linkend="func-ref-comedi-dio-read"><function>comedi_dio_read</function></link>
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and <link linkend="func-ref-comedi-dio-write"><function>comedi_dio_write</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-dio-read"><function>comedi_dio_read</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_dio_read</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int *<parameter>bit</parameter></paramdef>
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</funcprototype></funcsynopsis>
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-dio-write"><function>comedi_dio_write</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_dio_write</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int <parameter>bit</parameter></paramdef>
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@ -84,12 +85,12 @@ acquisition. The integer <parameter class="function">bit</parameter>
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contains the value of the acquired bit.
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</para>
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<para>
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The direction of bidirectional lines can be configured using
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the function
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The direction of bidirectional lines can be configured using the function
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<link linkend="func-ref-comedi-dio-config"><function>comedi_dio_config</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-dio-config"><function>comedi_dio_config</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_dio_config</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int <parameter>dir</parameter></paramdef>
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@ -105,11 +106,11 @@ the entire block.
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<para>
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Multiple channels can be read and written simultaneously using the
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function
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function <link linkend="func-ref-comedi-dio-bitfield2"><function>comedi_dio_bitfield2</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-dio-bitfield2"><function>comedi_dio_bitfield2</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_dio_bitfield2</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>write_mask</parameter></paramdef>
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<paramdef>unsigned int *<parameter>bits</parameter></paramdef>
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@ -160,56 +161,76 @@ Single analog acquisition
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Analog &comedi; channels can produce data values that are
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<emphasis>samples</emphasis> from continuous analog signals.
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These samples are integers with a significant content in
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the range of, typically, <literal>8</literal>, <literal>10</literal>,
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<literal>12</literal>, or <literal>16</literal> bits.
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the range of, typically, 8, 10, 12, or 16 bits.
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</para>
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<para>
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The function
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Single samples can be read from an analog channel using the function
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<link linkend="func-ref-comedi-data-read"><function>comedi_data_read</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-data-read"><function>comedi_data_read</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_data_read</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int <parameter>range</parameter></paramdef>
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<paramdef>unsigned int <parameter>aref</parameter></paramdef>
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<paramdef><link linkend="ref-type-lsampl-t">lsampl_t</link> *<parameter>data</parameter></paramdef>
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<paramdef>lsampl_t *<parameter>data</parameter></paramdef>
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</funcprototype></funcsynopsis>
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reads one such data value from a &comedi; channel, and puts it in
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the user-specified <parameter>data</parameter> buffer. The function
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This reads one such data value from a &comedi; channel, and puts it in
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the user-specified <parameter>data</parameter> buffer.
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</para>
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<para>
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In the opposite direction, single samples can be written to an analog output
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channel using the function
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<link linkend="func-ref-comedi-data-write"><function>comedi_data_write</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-data-write"><function>comedi_data_write</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_data_write</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int <parameter>range</parameter></paramdef>
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<paramdef>unsigned int <parameter>aref</parameter></paramdef>
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<paramdef><link linkend="ref-type-lsampl-t">lsampl_t</link> <parameter>data</parameter></paramdef>
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<paramdef>lsampl_t <parameter>data</parameter></paramdef>
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</funcprototype></funcsynopsis>
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</para>
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works in the opposite direction. Data values returned by this function
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<para>
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Raw data values read or written by the above functions
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are unsigned integers less than, or equal to, the maximum sample value
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of the channel, which can be determined using the function
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<link linkend="func-ref-comedi-get-maxdata"><function>comedi_get_maxdata</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef><link linkend="ref-type-lsampl-t">lsampl_t</link> <link linkend="func-ref-comedi-get-maxdata"><function>comedi_get_maxdata</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>lsampl_t <function>comedi_get_maxdata</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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</funcprototype></funcsynopsis>
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Conversion of data values to physical units can be performed by the
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function
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Conversion between raw data values and uncalibrated physical units can
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be performed by the functions
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<link linkend="func-ref-comedi-to-phys"><function>comedi_to_phys</function></link>
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and <link linkend="func-ref-comedi-from-phys"><function>comedi_from_phys</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>double <link linkend="func-ref-comedi-to-phys"><function>comedi_to_phys</function></link></funcdef>
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<paramdef><link linkend="ref-type-lsampl-t">lsampl_t</link> <parameter>data</parameter></paramdef>
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<paramdef><link linkend="ref-type-comedi-range">comedi_range</link> *<parameter>range</parameter></paramdef>
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<paramdef><link linkend="ref-type-lsampl-t">lsampl_t</link> <parameter>maxdata</parameter></paramdef>
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<funcdef>double <function>comedi_to_phys</function></funcdef>
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<paramdef>lsampl_t <parameter>data</parameter></paramdef>
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<paramdef>comedi_range *<parameter>range</parameter></paramdef>
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<paramdef>lsampl_t <parameter>maxdata</parameter></paramdef>
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</funcprototype></funcsynopsis>
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<funcsynopsis><funcprototype>
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<funcdef>lsampl_t <function>comedi_from_phys</function></funcdef>
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<paramdef>double <parameter>data</parameter></paramdef>
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<paramdef>comedi_range *<parameter>range</parameter></paramdef>
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<paramdef>lsampl_t <parameter>maxdata</parameter></paramdef>
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</funcprototype></funcsynopsis>
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</para>
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<para>
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There are two data structures in these commands that are not fully
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self-explanatory:
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<itemizedlist>
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@ -245,16 +266,17 @@ Each single acquisition by, for example,
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requires quite some overhead, because all the arguments of the
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function call are checked. If multiple acquisitions must be done on
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the same channel, this overhead can be avoided by using a function
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that can read more than one sample:
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that can read more than one sample,
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<link linkend="func-ref-comedi-data-read-n"><function>comedi_data_read_n</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-data-read-n"><function>comedi_data_read_n</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_data_read_n</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int <parameter>range</parameter></paramdef>
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<paramdef>unsigned int <parameter>aref</parameter></paramdef>
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<paramdef><link linkend="ref-type-lsampl-t">lsampl_t</link> *<parameter>data</parameter></paramdef>
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<paramdef>lsampl_t *<parameter>data</parameter></paramdef>
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<paramdef>unsigned int <parameter>n</parameter></paramdef>
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</funcprototype></funcsynopsis>
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@ -263,20 +285,23 @@ limited by the &comedi; implementation (to a maximum of 100 samples),
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because the call is blocking.
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</para>
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<para>
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The start of the data acquisition can also be delayed by a specified
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number of nano-seconds:
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The start of the a single data acquisition can also be delayed by a specified
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number of nano-seconds using the function
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<link linkend="func-ref-comedi-data-read-delayed"><function>comedi_data_read_delayed</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-data-read-delayed"><function>comedi_data_read_delayed</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<funcdef>int <function>comedi_data_read_delayed</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
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<paramdef>unsigned int <parameter>channel</parameter></paramdef>
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<paramdef>unsigned int <parameter>range</parameter></paramdef>
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<paramdef>unsigned int <parameter>aref</parameter></paramdef>
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<paramdef><link linkend="ref-type-lsampl-t">lsampl_t</link> *<parameter>data</parameter></paramdef>
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<paramdef>lsampl_t *<parameter>data</parameter></paramdef>
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<paramdef>unsigned int <parameter>nano_sec</parameter></paramdef>
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</funcprototype></funcsynopsis>
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</para>
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<para>
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All these read and write acquisition functions are implemented on top
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of the generic <link linkend="instructions">instruction</link>
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command.
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@ -320,7 +345,7 @@ All the information needed to execute an instruction is stored in the
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<link linkend="ref-type-comedi-insn">comedi_insn</link>
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data structure:
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<programlisting>
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struct <anchor id="insn-data-structure"/>comedi_insn_struct {
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typedef struct <anchor id="insn-data-structure"/>comedi_insn_struct {
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<anchor id="insn-data-structure-insn"/>unsigned int insn; // integer encoding the type of acquisition
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// (or configuration)
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unsigned int n; // number of elements in data array
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@ -393,29 +418,42 @@ Instruction execution
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<para>
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Once an instruction data structure has been filled in, the
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corresponding instruction is executed with the function
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<link linkend="func-ref-comedi-do-insn"><function>comedi_do_insn</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-do-insn"><function>comedi_do_insn</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<paramdef><link linkend="ref-type-comedi-insn">comedi_insn</link> *<parameter>instruction</parameter></paramdef>
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<funcdef>int <function>comedi_do_insn</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>comedi_insn *<parameter>instruction</parameter></paramdef>
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</funcprototype></funcsynopsis>
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Many &comedi; instructions are shortcuts that relieve the programmer
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from explicitly filling in the data structure and calling the
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<link linkend="func-ref-comedi-do-insn">comedi_do_insn</link>
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<link linkend="func-ref-comedi-do-insn"><function>comedi_do_insn</function></link>
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function.
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</para>
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<para>
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The function
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A list of instructions can be executed in one function call using the function
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<link linkend="func-ref-comedi-do-insnlist"><function>comedi_do_insnlist</function></link>:
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<funcsynopsis><funcprototype>
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<funcdef>int <link linkend="func-ref-comedi-do-insnlist"><function>comedi_do_insnlist</function></link></funcdef>
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<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
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<paramdef><link linkend="ref-type-comedi-insnlist">comedi_insnlist</link> *<parameter>list</parameter></paramdef>
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<funcdef>int <function>comedi_do_insnlist</function></funcdef>
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<paramdef>comedi_t *<parameter>device</parameter></paramdef>
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<paramdef>comedi_insnlist *<parameter>list</parameter></paramdef>
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</funcprototype></funcsynopsis>
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allows to perform a list of instructions in one function
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call. The number of instructions in the list is limited in the
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The parameter <parameter class="function">list</parameter> is a pointer to a
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<link linkend="insnlist-data-structure"><type>comedi_insnlist</type></link>
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data structure holding a pointer to an array of <type>comedi_insn</type>
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and the number of instructions in the list:
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<programlisting>
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typedef struct <anchor id="insnlist-data-structure"/>comedi_insnlist_struct {
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unsigned int n_insns;
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comedi_insn *insns;
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} comedi_insnlist;
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</programlisting>
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</para>
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<para>
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The number of instructions in the list is limited in the
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implementation, because instructions are executed
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<emphasis>synchronously</emphasis>, i.e., the call blocks until the
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whole instruction (list) has finished.
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@ -484,8 +522,9 @@ each type of configuration instruction.
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<row>
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<entry><constant>INSN_CONFIG_DIO_INPUT</constant></entry>
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<entry>
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Configure a dio line as input. It is easier to use comedi_dio_config() than
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to use this configuration instruction directly.
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Configure a DIO line as input. It is easier to use
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<link linkend="func-ref-comedi-dio-config"><function>comedi_dio_config</function>()</link>
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than to use this configuration instruction directly.
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</entry>
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<entry>1</entry>
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<entry>
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@ -495,8 +534,9 @@ n/a
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<row>
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<entry><constant>INSN_CONFIG_DIO_OUTPUT</constant></entry>
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<entry>
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Configure a dio line as output. It is easier to use comedi_dio_config() than
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to use this configuration instruction directly.
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Configure a DIO line as output. It is easier to use
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<link linkend="func-ref-comedi-dio-config"><function>comedi_dio_config</function>()</link>
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than to use this configuration instruction directly.
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</entry>
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<entry>1</entry>
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<entry>
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@ -506,13 +546,13 @@ n/a
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<row>
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<entry><constant>INSN_CONFIG_ALT_SOURCE</constant></entry>
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<entry>
|
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Select an alternate input source. This instruction is
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used by comedi_calibrate to configure analog input channels
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Select an alternate input source. This instruction is used by calibration
|
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programs to configure analog input channels
|
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which can be redirected to read internal calibration
|
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references. You need to set the CR_ALT_SOURCE flag in the chanspec
|
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references. You need to set the <constant>CR_ALT_SOURCE</constant> flag in the chanspec
|
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when reading to actually read from the configured alternate input source.
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If you are using comedi_data_read(), then the channel parameter can be
|
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bitwise or'd with the CR_ALT_SOURCE flag.
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If you are using <function>comedi_data_read</function>(), then the channel parameter can be
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bitwise or'd with the <constant>CR_ALT_SOURCE</constant> flag.
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</entry>
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<entry>2</entry>
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<entry>
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@ -539,8 +579,9 @@ acts purely as a query if the block size is set to zero.
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<row>
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<entry><constant>INSN_CONFIG_DIO_QUERY</constant></entry>
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<entry>
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Queries the configuration of a dio line to see if it is an input or output.
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It is probably easier to use the comedilib function comedi_dio_get_config()
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Queries the configuration of a DIO line to see if it is an input or output.
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It is probably easier to use the comedilib function
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<link linkend="func-ref-comedi-dio-get-config"><function>comedi_dio_get_config</function>()</link>
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than to use this instruction directly.
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</entry>
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<entry>2</entry>
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@ -554,7 +595,7 @@ data[1]: The instruction sets this element to either
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</informaltable>
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<para>
|
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See the comedilib demo program demo/choose_clock.c for an example
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See the comedilib demo program <filename>demo/choose_clock.c</filename> for an example
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of using a configuration instruction.
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</para>
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@ -664,23 +705,24 @@ Executing a command
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</title>
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<para>
|
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A command is executed by the following &comedi; function:
|
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A command is executed by the function
|
||||
<link linkend="func-ref-comedi-command"><function>comedi_command</function></link>:
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|
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<funcsynopsis><funcprototype>
|
||||
<funcdef>int <link linkend="func-ref-comedi-command"><function>comedi_command</function></link></funcdef>
|
||||
<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
|
||||
<paramdef><link linkend="ref-type-comedi-cmd">comedi_cmd</link> *<parameter>command</parameter></paramdef>
|
||||
<funcdef>int <function>comedi_command</function></funcdef>
|
||||
<paramdef>comedi_t *<parameter>device</parameter></paramdef>
|
||||
<paramdef>comedi_cmd *<parameter>command</parameter></paramdef>
|
||||
</funcprototype></funcsynopsis>
|
||||
|
||||
The following sections explain the meaning of the
|
||||
<link linkend="ref-type-comedi-cmd">comedi_cmd</link> data structure.
|
||||
<link linkend="ref-type-comedi-cmd"><type>comedi_cmd</type></link> data structure.
|
||||
Filling in this structure can be quite complicated, and
|
||||
requires good knowledge about the exact functionalities of the DAQ
|
||||
card. So, before launching a command, the application programmer is
|
||||
adviced to check whether this complex command data structure can be
|
||||
successfully parsed. So, the typical sequence for executing a command is
|
||||
to first send the command through
|
||||
<link linkend="func-ref-comedi-command-test">comedi_command_test()</link>
|
||||
<link linkend="func-ref-comedi-command-test"><function>comedi_command_test</function>()</link>
|
||||
once or twice. The test will check that the command is valid for the
|
||||
particular device, and often makes some adjustments to the command
|
||||
arguments, which can then be read back by the user to see the actual
|
||||
|
|
@ -689,7 +731,7 @@ values used.
|
|||
<para>
|
||||
A &comedi; program can find out on-line what the command capabilities
|
||||
of a specific device are, by means of the
|
||||
<link linkend="func-ref-comedi-get-cmd-src-mask">comedi_get_cmd_src_mask()</link>
|
||||
<link linkend="func-ref-comedi-get-cmd-src-mask"><function>comedi_get_cmd_src_mask</function>()</link>
|
||||
function.
|
||||
</para>
|
||||
|
||||
|
|
@ -703,7 +745,7 @@ The command data structure
|
|||
<para>
|
||||
The command executes according to the information about the requested
|
||||
acquisition, which is stored in the
|
||||
<link linkend="ref-type-comedi-cmd">comedi_cmd</link>
|
||||
<link linkend="ref-type-comedi-cmd"><type>comedi_cmd</type></link>
|
||||
<anchor id="command-data-struct"/>data structure:
|
||||
<programlisting>
|
||||
typedef struct comedi_cmd_struct comedi_cmd;
|
||||
|
|
@ -745,16 +787,16 @@ so-called <emphasis>event</emphasis>. More on these in
|
|||
|
||||
<para>
|
||||
The <parameter class="function">subdev</parameter> member of the
|
||||
<link linkend="ref-type-comedi-cmd">comedi_cmd</link> structure is
|
||||
<link linkend="ref-type-comedi-cmd"><type>comedi_cmd</type></link> structure is
|
||||
the index of the subdevice the command is intended for. The
|
||||
<link linkend="func-ref-comedi-find-subdevice-by-type">comedi_find_subdevice_by_type()</link>
|
||||
<link linkend="func-ref-comedi-find-subdevice-by-type"><function>comedi_find_subdevice_by_type</function>()</link>
|
||||
function can be useful in discovering the index of your desired subdevice.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The <link linkend="command-data-struct-chanlist">chanlist</link>
|
||||
member of the
|
||||
<link linkend="ref-type-comedi-cmd">comedi_cmd</link> data
|
||||
<link linkend="ref-type-comedi-cmd"><type>comedi_cmd</type></link> data
|
||||
structure should point to an array whose number of elements is
|
||||
specificed by
|
||||
<link linkend="command-data-struct-chanlist-len">chanlist_len</link>
|
||||
|
|
@ -767,9 +809,7 @@ that should be stepped through for each scan. The elements of the
|
|||
<link linkend="command-data-struct-chanlist">chanlist</link> array should be
|
||||
initialized by <quote>packing</quote> the channel, range and reference
|
||||
information together with the
|
||||
<parameter class="function">
|
||||
<link linkend="ref-macro-CR-PACK">CR_PACK()</link>
|
||||
</parameter>
|
||||
<link linkend="ref-macro-CR-PACK"><function>CR_PACK</function>()</link>
|
||||
macro.
|
||||
</para>
|
||||
|
||||
|
|
@ -785,7 +825,7 @@ the buffer where the driver should write/read its data to/from.
|
|||
|
||||
<para>
|
||||
The final member of the
|
||||
<link linkend="command-data-struct">comedi_cmd</link> structure is the
|
||||
<link linkend="command-data-struct"><type>comedi_cmd</type></link> structure is the
|
||||
<link linkend="command-data-struct-flags">flags</link> field,
|
||||
i.e., bits in a word that can be bitwise-or'd together. The meaning of
|
||||
these bits are explained in a
|
||||
|
|
@ -813,10 +853,10 @@ start a <link linkend="scan">scan</link>, start a
|
|||
the acquisition. Each event can be given its own
|
||||
<emphasis><link linkend="source.trigger.anchor">source</link></emphasis>
|
||||
(the <parameter class="function">*_src</parameter> members in the
|
||||
<link linkend="ref-type-comedi-cmd">comedi_cmd</link> data
|
||||
<link linkend="ref-type-comedi-cmd"><type>comedi_cmd</type></link> data
|
||||
structure). And each event source can have a corresponding
|
||||
argument (the <parameter class="function">*_arg</parameter> members of
|
||||
the <link linkend="ref-type-comedi-cmd">comedi_cmd</link> data
|
||||
the <link linkend="ref-type-comedi-cmd"><type>comedi_cmd</type></link> data
|
||||
structure) whose meaning depends on the type of source trigger.
|
||||
For example, to specify an external digital line <quote>3</quote> as a
|
||||
source (in general, <emphasis>any</emphasis> of the five event
|
||||
|
|
@ -842,10 +882,8 @@ The available options are:
|
|||
<link linkend="command-data-struct-start-src">start_src</link>
|
||||
event occurs
|
||||
<link linkend="command-data-struct-start-arg">start_arg</link>
|
||||
nanoseconds after the
|
||||
<link linkend="ref-type-comedi-cmd">comedi_cmd</link>
|
||||
is called. Currently, only
|
||||
<link linkend="command-data-struct-start-arg">start_arg</link>=0 is
|
||||
nanoseconds after the command is set up. Currently, only
|
||||
<link linkend="command-data-struct-start-arg">start_arg</link>=<literal>0</literal> is
|
||||
supported.
|
||||
</para>
|
||||
</listitem>
|
||||
|
|
@ -1048,7 +1086,7 @@ Not all event sources are applicable to all events. Supported
|
|||
trigger sources for specific events depend significantly on your
|
||||
particular device, and even more on the current state of its device
|
||||
driver. The
|
||||
<link linkend="func-ref-comedi-get-cmd-src-mask">comedi_get_cmd_src_mask()</link>
|
||||
<link linkend="func-ref-comedi-get-cmd-src-mask"><function>comedi_get_cmd_src_mask</function>()</link>
|
||||
function is useful for determining what trigger sources a subdevice
|
||||
supports.
|
||||
</para>
|
||||
|
|
@ -1174,7 +1212,7 @@ device that could do either input or output.
|
|||
<anchor id="trig-other"/>
|
||||
<constant>TRIG_CONFIG</constant>: perform configuration, not triggering.
|
||||
This is a legacy of the deprecated
|
||||
<link linkend="ref-type-comedi-cmd">comedi_trig_struct</link>
|
||||
<link linkend="ref-type-comedi-trig"><type>comedi_trig_struct</type></link>
|
||||
data structure, and has no function at present.
|
||||
</para>
|
||||
</listitem>
|
||||
|
|
@ -1228,7 +1266,7 @@ Sometimes, your input channels change slowly enough that
|
|||
you are able to average many successive input values to get a
|
||||
more accurate measurement of the actual value. In general,
|
||||
the more samples you average, the better your estimate
|
||||
gets, roughly by a factor of sqrt(number_of_samples).
|
||||
gets, roughly by a factor of <function>sqrt</function>(number_of_samples).
|
||||
Obviously, there are limitations to this:
|
||||
</para>
|
||||
|
||||
|
|
@ -1282,18 +1320,18 @@ to help you in your quest to accurately measure slowly varying
|
|||
inputs:
|
||||
|
||||
<funcsynopsis><funcprototype>
|
||||
<funcdef>int <link linkend="func-ref-comedi-sv-init"><function>comedi_sv_init</function></link></funcdef>
|
||||
<paramdef><link linkend="ref-type-comedi-sv-t">comedi_sv_t</link> *<parameter>sv</parameter></paramdef>
|
||||
<paramdef><link linkend="ref-type-comedi-t">comedi_t</link> *<parameter>device</parameter></paramdef>
|
||||
<funcdef>int <function>comedi_sv_init</function></funcdef>
|
||||
<paramdef>comedi_sv_t *<parameter>sv</parameter></paramdef>
|
||||
<paramdef>comedi_t *<parameter>device</parameter></paramdef>
|
||||
<paramdef>unsigned int <parameter>subdevice</parameter></paramdef>
|
||||
<paramdef>unsigned int <parameter>channel</parameter></paramdef>
|
||||
</funcprototype></funcsynopsis>
|
||||
|
||||
This function initializes the
|
||||
<link linkend="ref-type-comedi-sv-t">comedi_sv_t</link> data structure, used
|
||||
The above function <link linkend="func-ref-comedi-sv-init"><function>comedi_sv_init</function></link> initializes the
|
||||
<link linkend="ref-type-comedi-sv-t"><type>comedi_sv_t</type></link> data structure, used
|
||||
to do the averaging acquisition:
|
||||
<programlisting>
|
||||
struct comedi_sv_struct {
|
||||
typedef struct comedi_sv_struct {
|
||||
<link linkend="ref-type-comedi-t">comedi_t</link> *dev;
|
||||
unsigned int subdevice;
|
||||
unsigned int chan;
|
||||
|
|
@ -1306,19 +1344,20 @@ struct comedi_sv_struct {
|
|||
int n;
|
||||
|
||||
lsampl_t maxdata;
|
||||
};
|
||||
} comedi_sv_t;
|
||||
</programlisting>
|
||||
|
||||
The actual acquisition is done with the function
|
||||
<link linkend="func-ref-comedi-sv-measure"><function>comedi_sv_measure</function></link>:
|
||||
|
||||
<funcsynopsis><funcprototype>
|
||||
<funcdef>int <link linkend="func-ref-comedi-sv-measure"><function>comedi_sv_measure</function></link></funcdef>
|
||||
<paramdef><link linkend="ref-type-comedi-sv-t">comedi_sv_t</link> *<parameter>sv</parameter></paramdef>
|
||||
<funcdef>int <function>comedi_sv_measure</function></funcdef>
|
||||
<paramdef>comedi_sv_t *<parameter>sv</parameter></paramdef>
|
||||
<paramdef>double *<parameter>data</parameter></paramdef>
|
||||
</funcprototype></funcsynopsis>
|
||||
|
||||
The number of samples over which the
|
||||
<function>comedi_sv_measure()</function> averages is limited by the
|
||||
The number of samples over which the function
|
||||
<function>comedi_sv_measure</function>() averages is limited by the
|
||||
implementation (currently the limit is 100 samples).
|
||||
</para>
|
||||
|
||||
|
|
@ -1927,11 +1966,13 @@ Each of these signal lines
|
|||
can be configured as an input or output, and the signal appearing on the output
|
||||
of each line can be configured to one of several internal board timing signals
|
||||
(although on older boards RTSI line 7 can only be used for the clock signal).
|
||||
The ni_pcimio, ni_atmio, and ni_mio_cs drivers expose the RTSI bus
|
||||
The <systemitem>ni_pcimio</systemitem>, <systemitem>ni_atmio</systemitem>, and
|
||||
<systemitem>ni_mio_cs</systemitem> drivers expose the RTSI bus
|
||||
as a digital I/O subdevice (subdevice number 10).
|
||||
</para>
|
||||
<para>
|
||||
The functions comedi_dio_config() and comedi_dio_get_config() can be used on
|
||||
The functions <function>comedi_dio_config</function>() and
|
||||
<function>comedi_dio_get_config()</function> can be used on
|
||||
the RTSI subdevice to
|
||||
set/query the direction (input or output) of each of the RTSI lines individually.
|
||||
</para>
|
||||
|
|
@ -1941,7 +1982,7 @@ The subdevice also supports the
|
|||
<constant>INSN_CONFIG_GET_CLOCK_SRC</constant> configuration
|
||||
instructions, which can be
|
||||
used to configure/query what source the board uses to synchronize its
|
||||
master clock to. The various possibilities are defined in the comedi.h
|
||||
master clock to. The various possibilities are defined in the <filename>comedi.h</filename>
|
||||
header file:
|
||||
</para>
|
||||
<informaltable>
|
||||
|
|
@ -1964,7 +2005,7 @@ Use the board's internal oscillator.
|
|||
<entry>
|
||||
Use the RTSI line 7 as the master clock. This source is
|
||||
only supported on pre-m-series boards. The newer m-series boards
|
||||
use NI_MIO_PLL_RTSI_CLOCK() instead.
|
||||
use <function>NI_MIO_PLL_RTSI_CLOCK</function>() instead.
|
||||
</entry>
|
||||
</row>
|
||||
<row>
|
||||
|
|
@ -2010,7 +2051,7 @@ Finally, the configuration instructions
|
|||
<constant>INSN_CONFIG_SET_ROUTING</constant> and
|
||||
<constant>INSN_CONFIG_GET_ROUTING</constant>
|
||||
can be used to select/query which internal signal
|
||||
will appear on a given RTSI output line. The header file comedi.h defines
|
||||
will appear on a given RTSI output line. The header file <filename>comedi.h</filename> defines
|
||||
the following signal sources which can be routed to an RTSI line:
|
||||
</para>
|
||||
|
||||
|
|
@ -2107,8 +2148,8 @@ signal.
|
|||
The RTSI bus pins may be used as trigger inputs for many of the
|
||||
&comedi; trigger functions. To use the RTSI bus pins, set the source to be
|
||||
<constant>TRIG_EXT</constant> and the source argument using the return values
|
||||
from the <function>NI_EXT_RTSI()</function> function (or similarly the
|
||||
<function>NI_EXT_PFI()</function> function if you want
|
||||
from the <function>NI_EXT_RTSI</function>() function (or similarly the
|
||||
<function>NI_EXT_PFI</function>() function if you want
|
||||
to trigger from a PFI line). The <constant>CR_EDGE</constant> and
|
||||
<constant>CR_INVERT</constant> flags may
|
||||
also be set on the trigger source argument to specify edge and
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue