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TITLE=" Low-level drivers
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SUMMARY="Header navigation table"
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>Control and Measurement Device Interface</I
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NAME="COMEDIREFERENCE"
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HREF="x3563.html#CONSTANTSMACROS"
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>constants and macros</A
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HREF="x3563.html#DATATYPESSTRUCTURES"
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>data types and structures</A
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HREF="x3563.html#FUNCTIONREFERENCE"
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NAME="COMEDI-COMEDILIB-H"
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>7.1. Headerfiles: <TT
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>application programs</A
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include the header file <TT
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>.) They contain the full
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interface of <ACRONYM
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>: defines, function prototypes, data structures.</P
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>The following Sections give more details.</P
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NAME="CONSTANTSMACROS"
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>7.2. Constants and Macros</A
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NAME="REF-MACRO-CR-PACK"
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>CR_PACK is used to initialize the elements of the
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HREF="x3563.html#REF-TYPE-COMEDI-CMD"
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HREF="x3563.html#REF-TYPE-COMEDI-INSN"
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CLASS="PROGRAMLISTING"
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>#define CR_PACK(chan,rng,aref) ( (((aref)&0x3)<<24) | (((rng)&0xff)<<16) | (chan) ) </PRE
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> argument is the channel you wish to
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use, with the channel numbering starting at zero.</P
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> is an index, starting at zero,
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whose meaning is device dependent. The
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>comedi_get_n_ranges()</A
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>comedi_get_range()</A
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functions are useful in discovering information about the available
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> argument indicates what reference you
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want the device to use. It can be any of the following:
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> is for inputs/outputs referenced to ground.
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> reference (the low inputs of all the
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channels are tied together, but are isolated from ground).
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> is for differential inputs/outputs.
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> is for any reference that does not fit into the above categories.
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Particular drivers may or may not use the AREF flags. If they are
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not supported, they are silently ignored.</P
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NAME="REF-MACRO-RANGE-LENGTH"
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>7.2.2. RANGE_LENGTH (deprecated)</A
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>Rangetype values are library-internal tokens that represent an
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array of range information structures. These numbers are primarily
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used for communication between the kernel and library.</P
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>The RANGE_LENGTH() macro returns the length of the array that is
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specified by the rangetype token.</P
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>The RANGE_LENGTH() macro is deprecated, and should not be used in
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new applications. It is scheduled to be removed from the header
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file at version 1.0. Binary compatibility may be broken for version
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NAME="DATATYPESSTRUCTURES"
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>7.3. Data Types and Structures</A
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>This Section explains the data structures that users of the <ACRONYM
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API are confronted with:
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CLASS="PROGRAMLISTING"
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>typedef struct subdevice_struct <A
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HREF="x3563.html#REF-TYPE-SUBDEVICE-STRUCT"
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typedef struct comedi_devinfo_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-DEVINFO"
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typedef struct comedi_t_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-T"
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typedef struct sampl_t_struct <A
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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typedef struct lsampl_t_struct <A
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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typedef struct comedi_sv_t_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-SV-T"
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typedef struct comedi_cmd_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-CMD"
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typedef struct comedi_insn_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-INSN"
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typedef struct comedi_range_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-RANGE"
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typedef struct comedi_krange_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-KRANGE"
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typedef struct comedi_insnlist_struct <A
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HREF="x3563.html#REF-TYPE-COMEDI-INSNLIST"
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The data structures used in the implementation of the <ACRONYM
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HREF="x1283.html#DRIVERDATASTRUCTURES"
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NAME="REF-TYPE-SUBDEVICE-STRUCT"
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>7.3.1. subdevice_struct</A
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>subdevice_struct</VAR
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information about a subdevice. This structure is usually filled in
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automatically when the driver is loaded (<SPAN
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programmers need not access this data structure directly.
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CLASS="PROGRAMLISTING"
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>typedef struct subdevice_struct <A
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NAME="REF-TYPE-SUBDEVICE"
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struct subdevice_struct{
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unsigned int subd_flags;
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unsigned int timer_type;
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unsigned int len_chanlist;
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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unsigned int range_type;
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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unsigned int *range_type_list;
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unsigned int *flags_list;
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HREF="x3563.html#REF-TYPE-COMEDI-RANGE"
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HREF="x3563.html#REF-TYPE-COMEDI-RANGE"
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unsigned int has_cmd;
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unsigned int has_insn_bits;
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HREF="x3563.html#REF-TYPE-COMEDI-CMD"
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HREF="x3563.html#REF-TYPE-COMEDI-CMD"
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NAME="REF-TYPE-COMEDI-DEVINFO"
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>7.3.2. comedi_devinfo</A
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information about a device. This structure is usually filled in
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automatically when the driver is loaded (<SPAN
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programmers need not access this data structure directly.
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_devinfo_struct comedi_devinfo;
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struct comedi_devinfo_struct{
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unsigned int version_code; // version number of the Comedi code
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unsigned int n_subdevs; // number of subdevices on this device
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char driver_name[COMEDI_NAMELEN];
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char board_name[COMEDI_NAMELEN];
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int read_subdevice; // number of read devices
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int write_subdevice; // number of write devices
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NAME="REF-TYPE-COMEDI-T"
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> is used to represent an
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_t_struct comedi_t;
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struct comedi_t_struct{
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int magic; // driver-specific magic number, for identification
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int fd; // file descriptor, for open() and close()
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int n_subdevices; // number of subdevices on this device
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HREF="x3563.html#REF-TYPE-COMEDI-DEVINFO"
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HREF="x3563.html#REF-TYPE-SUBDEVICE"
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> *subdevices; // pointer to subdevice list
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// filled in automatically at load time
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unsigned int has_insnlist_ioctl; // can process <A
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HREF="x621.html#ANCHOR.INSTRUCTION.LIST"
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>instruction lists</A
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unsigned int has_insn_ioctl; // can process <A
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HREF="x621.html#INSTRUCTIONS"
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> pointer is returned by a
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and should be used for subsequent access to the device.
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It is a transparent type, and pointers to type
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should not be dereferenced by the application.</P
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NAME="REF-TYPE-SAMPL-T"
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CLASS="PROGRAMLISTING"
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>typedef unsigned short sampl_t;</PRE
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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types used to represent data values in Comedilib. It is used in a few
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places where a data type
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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useful. On most architectures,
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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is defined to be <VAR
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>Most drivers represent data transferred by <CODE
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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Applications should check the subdevice flag
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SDF_LSAMPL to determine if the subdevice uses
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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NAME="REF-TYPE-LSAMPL-T"
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CLASS="PROGRAMLISTING"
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>typedef unsigned int lsampl_t;</PRE
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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is the data type typically used to represent
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data values in libcomedi. On most architectures,
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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is defined to be uint32.</P
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NAME="REF-TYPE-COMEDI-TRIG"
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>7.3.6. comedi_trig (deprecated)</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_trig_struct comedi_trig;
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struct comedi_trig_struct{
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unsigned int subdev; /* subdevice */
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unsigned int mode; /* mode */
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unsigned int n_chan; /* number of channels */
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unsigned int *chanlist; /* channel/range list */
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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> *data; /* data list, size depends on subd flags */
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unsigned int n; /* number of scans */
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unsigned int trigsrc;
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unsigned int trigvar;
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unsigned int trigvar1;
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unsigned int data_len;
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unsigned int unused[3];
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>The comedi_trig structure is a control structure used by the
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COMEDI_TRIG ioctl, an older method of communicating
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instructions to the driver and hardware. Use of comedi_trig is
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deprecated, and should not be used in new applications.</P
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NAME="REF-TYPE-COMEDI-SV-T"
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>7.3.7. comedi_sv_t</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_sv_struct comedi_sv_t;
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struct comedi_sv_struct{
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unsigned int subdevice;
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/* number of measurements to average (for ai) */
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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>The comedi_sv_t structure is used by the comedi_sv_*()
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functions to provide a simple method of accurately measuring
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slowly varying inputs. See the relevant section for more
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NAME="REF-TYPE-COMEDI-CMD"
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>7.3.8. comedi_cmd</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_cmd_struct comedi_cmd;
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struct comedi_cmd_struct{
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unsigned int start_src;
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unsigned int start_arg;
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unsigned int scan_begin_src;
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unsigned int scan_begin_arg;
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unsigned int convert_src;
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unsigned int convert_arg;
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unsigned int scan_end_src;
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unsigned int scan_end_arg;
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unsigned int stop_src;
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unsigned int stop_arg;
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unsigned int *chanlist;
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unsigned int chanlist_len;
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HREF="x3563.html#REF-TYPE-SAMPL-T"
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unsigned int data_len;
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>More information on using commands can be found in the
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NAME="REF-TYPE-COMEDI-INSN"
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>7.3.9. comedi_insn</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_insn_struct comedi_insn;
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struct comedi_insn_struct{
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HREF="x3563.html#REF-TYPE-LSAMPL-T"
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unsigned int chanspec;
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unsigned int unused[3];
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>Comedi instructions are described by the comedi_insn structure.
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Applications send instructions to the driver in order to perform
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control and measurement operations that are done immediately or
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synchronously, i.e., the operations complete before program control
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returns to the application. In particular, instructions cannot
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describe acquisition that involves timers or external events.</P
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>The field insn determines the type of instruction that is sent
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to the driver. Valid instruction types are:</P
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>read values from an input channel
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>write values to an output channel
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>read/write values on multiple digital I/O channels
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>configure a subdevice
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>read a timestamp, identical to gettimeofday()
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>wait a specified number of nanoseconds
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>The number of samples to read or write, or the size of the configuration
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structure is specified by the field n, and the buffer for those
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samples by data. The field subdev is the subdevice index
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that the instruction is sent to. The field chanspec specifies
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the channel, range, and analog reference (if applicable).</P
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>Instructions can be sent to drivers using comedi_do_insn().
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Multiple instructions can be sent to drivers in the same system
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call using comedi_do_insnlist().</P
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NAME="REF-TYPE-COMEDI-RANGE"
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>7.3.10. comedi_range</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_range_struct comedi_range;
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struct comedi_range_struct{
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>The comedi_range structure conveys part of the information
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necessary to translate sample values to physical units, in particular,
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the endpoints of the range and the physical unit type. The
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physical unit type is specified by the field unit, which may
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take the values UNIT_volt for volts, UNIT_mA for milliamps,
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or UNIT_none for unitless. The endpoints are specified by
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the fields min and max.</P
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NAME="REF-TYPE-COMEDI-KRANGE"
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>7.3.11. comedi_krange</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_krange_struct comedi_krange;
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struct comedi_krange_struct{
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>The comedi_krange structure is used to transfer range information
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between the driver and Comedilib, and should not normally be used
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by applications. The structure conveys the same information as the
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comedi_range structure, except the fields min and max
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are integers, multiplied by a factor of 1000000 compared to the
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counterparts in comedi_range.</P
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>In addition, kcomedilib uses the comedi_krange structure in place
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of the comedi_range structure.</P
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NAME="REF-TYPE-COMEDI-INSNLIST"
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>7.3.12. comedi_insnlist</A
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CLASS="PROGRAMLISTING"
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>typedef struct comedi_insnlist_struct comedi_insnlist;
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struct comedi_insnlist_struct{
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unsigned int n_insns;
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>An instruction list (insnlist) structure is used to communicate
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a list of instructions.</P
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NAME="FUNCTIONREFERENCE"
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>7.4. Comedi Function Reference</A
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>Table of Contents</B
923
> -- close a Comedi device</DT
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> -- open a Comedi device</DT
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> -- change Comedilib logging properties</DT
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> -- print a Comedilib error message</DT
943
> -- return string describing Comedilib error code</DT
948
> -- number of last Comedilib error</DT
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> -- integer descriptor of Comedilib device</DT
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>comedi_get_n_subdevices</A
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> -- number of subdevices </DT
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>comedi_get_version_code</A
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> -- Comedi version code</DT
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>comedi_get_driver_name</A
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> -- Comedi driver name</DT
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>comedi_get_board_name</A
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> -- Comedi device name</DT
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>comedi_get_subdevice_type</A
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> -- type of subdevice</DT
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>comedi_find_subdevice_by_type</A
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> -- search for subdevice type</DT
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>comedi_get_read_subdevice</A
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> -- find streaming input subdevice</DT
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>comedi_get_write_subdevice</A
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> -- find streaming output subdevice</DT
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>comedi_get_subdevice_flags</A
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> -- properties of subdevice</DT
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>comedi_get_n_channels</A
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> -- number of subdevice channels</DT
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>comedi_range_is_chan_specific</A
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> -- range information depends on channel</DT
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>comedi_maxdata_is_chan_specific</A
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> -- maximum sample depends on channel</DT
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>comedi_get_maxdata</A
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> -- maximum sample of channel</DT
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>comedi_get_n_ranges</A
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> -- number of ranges of channel</DT
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>comedi_get_range</A
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> -- range information of channel</DT
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>comedi_find_range</A
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> -- search for range</DT
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>comedi_get_buffer_size</A
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> -- streaming buffer size of subdevice</DT
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>comedi_get_max_buffer_size</A
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> -- maximum streaming buffer size</DT
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>comedi_set_buffer_size</A
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> -- streaming buffer size of subdevice</DT
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> -- perform streaming input/output (deprecated)</DT
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>comedi_do_insnlist</A
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> -- perform multiple instructions</DT
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> -- perform instruction</DT
1068
> -- subdevice reservation</DT
1073
> -- subdevice reservation</DT
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> -- convert sample to physical units</DT
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>comedi_from_phys</A
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> -- convert physical units to sample</DT
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>comedi_data_read</A
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> -- read single sample from channel</DT
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>comedi_data_read_delayed</A
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> -- read single sample from channel after delaying for specified settling time</DT
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>comedi_data_read_hint</A
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> -- tell driver which channel/range/aref you are going to read from next</DT
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>comedi_data_write</A
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> -- write single sample to channel</DT
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>comedi_dio_config</A
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> -- change input/output properties of channel</DT
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> -- read single bit from digital channel</DT
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>comedi_dio_write</A
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> -- write single bit to digital channel</DT
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>comedi_dio_bitfield</A
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> -- read/write multiple digital channels</DT
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> -- slowly-varying inputs</DT
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>comedi_sv_update</A
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> -- slowly-varying inputs</DT
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>comedi_sv_measure</A
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> -- slowly-varying inputs</DT
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>comedi_get_cmd_src_mask</A
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> -- streaming input/output capabilities</DT
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>comedi_get_cmd_generic_timed</A
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> -- streaming input/output capabilities</DT
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> -- stop streaming input/output in progress</DT
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> -- start streaming input/output</DT
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>comedi_command_test</A
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> -- test streaming input/output configuration</DT
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> -- force updating of streaming buffer</DT
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>comedi_set_max_buffer_size</A
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> -- streaming buffer size of subdevice</DT
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>comedi_get_buffer_contents</A
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> -- streaming buffer status</DT
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>comedi_mark_buffer_read</A
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> -- streaming buffer status</DT
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>comedi_get_buffer_offset</A
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> -- streaming buffer status</DT
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>comedi_get_timer</A
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> -- timer information (deprecated)</DT
1197
>comedi_timed_1chan</A
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> -- streaming input (deprecated)</DT
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>comedi_set_global_oor_behavior</A
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> -- out-of-range behavior</DT
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>comedi_apply_calibration</A
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> -- set calibration from file</DT
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>comedi_apply_parsed_calibration</A
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> -- set calibration from memory</DT
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>comedi_cleanup_calibration_file</A
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> -- free calibration resources</DT
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>comedi_get_default_calibration_path</A
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> -- get default calibration file path</DT
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>comedi_parse_calibration_file</A
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> -- set calibration</DT
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SUMMARY="Footer navigation table"
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>Low-level drivers</TD
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