--- /dev/null
+ Comedi Documentation
+ David Schleef ds@stm.lbl.gov, Frank Hess fmhess@uiuc.edu
+
+
+ 1\b1.\b. I\bIn\bnt\btr\bro\bod\bdu\buc\bct\bti\bio\bon\bn
+
+ This is preliminary documentation for Comedi and Comedilib.
+
+
+ 2\b2.\b. I\bIn\bns\bst\bta\bal\bll\bla\bat\bti\bio\bon\bn a\ban\bnd\bd c\bco\bon\bnf\bfi\big\bgu\bur\bra\bat\bti\bio\bon\bn
+
+
+ This section covers compiling, installing, and configuring comedi and
+ comedlib.
+
+
+
+ 2\b2.\b.1\b1.\b. C\bCo\bom\bmp\bpi\bil\bli\bin\bng\bg a\ban\bnd\bd I\bIn\bns\bst\bta\bal\bll\bli\bin\bng\bg
+
+
+ This section has not been written.
+
+
+
+ 2\b2.\b.2\b2.\b. I\bIn\bns\bsm\bmo\bod\bd'\b'd\bdi\bin\bng\bg t\bth\bhe\be k\bke\ber\brn\bne\bel\bl m\bmo\bod\bdu\bul\ble\be
+
+
+ This section has not been written.
+
+
+
+ 2\b2.\b.3\b3.\b. C\bCo\bon\bnf\bfi\big\bgu\bur\bri\bin\bng\bg c\bco\bom\bme\bed\bdi\bi f\bfo\bor\br y\byo\bou\bur\br h\bha\bar\brd\bdw\bwa\bar\bre\be
+
+
+
+ I assume that your hardware device is in your computer, and that you
+ know the relevant details about it, i.e., what kind of card it is, the
+ I/O base, the IRQ, jumper settings related to input ranges, etc.
+
+ To tell the comedi kernel module that you have a particular device,
+ and some information about it, you will be running the comedi_config
+ command. Perhaps you should read the man page now.
+
+ In this tutorial, I will go through the process of configuring comedi
+ for two devices, a National Instruments AT-MIO-16E-10 and a Data
+ Translation DT2821-F-8DI.
+
+ The NI board is plug-and-play, and the man page tells me that I need
+ to configure the PnP part of the board with isapnptools. The
+ isapnptools package is a little cryptic, but the concepts are simple.
+ Once I learned how to use it, I settled on a /etc/isapnp.conf file
+ that contained the lines:
+
+
+
+ # ANSI string -->National Instruments, AT-MIO-16E-10<--
+ (CONFIGURE NIC2400/10725401 (LD 0
+ (IO 0 (BASE 0x0260))
+ (INT 0 (IRQ 3 (MODE +E)))
+ # (DMA 0 (CHANNEL 5))
+ # (DMA 1 (CHANNEL 6))
+ (ACT Y)
+ ))
+
+
+ It also contains a few lines about overall configuration and about my
+ sound card. I found out after a bit of trial-and-error that the NI
+ board does not always work with interrupts other than IRQ 3. YMMV.
+ Currently, the driver doesn't use DMA, but it may in the future, so I
+ commented out the DMA lines. It is a curious fact that the device
+ ignores the IRQ and DMA information given here, however, I keep the
+ information here to remind myself that the numbers aren't arbitrary.
+
+ When I run comedi_config (as root, of course), I provide the same
+ information. Since I want to have the board configured every time I
+ boot, I put the line
+
+
+
+ /usr/sbin/comedi_config /dev/comedi0 atmio-E 0x260,3
+
+
+
+ into /etc/rc.d/rc.local. You can, of course, run this command at a
+ command prompt. The man page tells me that the option list is
+ supposed to be "(I/O base),(IRQ)", so I used the same numbers as I put
+ in /etc/isapnp.conf, i.e., 0x260,3.
+
+ For the Data Translation board, I need to have a list of the jumper
+ settings. Fortunately, I wrote them all down in the manual -- I hope
+ they are still correct. However, I had to open the case to figure out
+ which board in the series I had. It is a DT2821-f-8di. The man page
+ of comedi_config tells me that I need to know the I/O base, IRQ, DMA
+ 1, DMA 2. However, since I wrote the driver, I know that it also
+ recognizes the differential/single-ended and unipolar/bipolar jumpers.
+ As always, the source is the final authority, and looking in
+ module/dt282x.c tells me that the options list is interpreted as:
+
+
+ +\bo I/O base
+
+ +\bo IRQ
+
+ +\bo 1=differential, 0=single ended
+
+ +\bo ai 0=unipolar, 1=bipolar
+
+ +\bo ao0 0=unipolar, 1=bipolar
+
+ +\bo ao1 0=unipolar, 1=bipolar
+
+ +\bo dma1
+
+ +\bo dma2
+
+ (ai=analog input, ao=analog output.) From this, I decide that the
+ appropriate options list is
+
+
+
+ 0x200,4,,1,1,1
+
+
+
+ I left the differential/single-ended number blank, since the driver
+ already knowns (from the board name), that it is differential. I
+ also left the DMA numbers blank, since I don't want the driver to use
+ DMA. (Don't want it to interfere with my sound card -- life is full
+ of difficult choices.) Keep in mind that things commented in the
+ source, but not in the documentation are about as likely to change as
+ the weather, so I put good comments next to the following line when I
+ put it in rc.local.
+
+
+
+ /usr/sbin/comedi_config /dev/comedi1 dt2821-f-8di 0x200,4,,1,1,1
+
+
+
+ So now I think that I have my boards configured correctly. Since data
+ acquisition boards are not typically well-engineered, comedi sometimes
+ can't figure out if the board is actually there. If it can't, it
+ assumes you are right. Both of these boards are well-made, so comedi
+ will give me an error message if it can't find them. The comedi
+ kernel module, since it is a part of the kernel, prints messages to
+ the kernel logs, which you can access through the command 'dmesg' or
+ /var/log/messages. Here is a configuration failure (from dmesg):
+
+
+
+ comedi0: ni_E: 0x0200 can't find board
+
+
+
+ When it does work, I get:
+
+
+
+ comedi0: ni_E: 0x0260 at-mio-16e-10 ( irq = 3 )
+
+
+
+ Note that it also correctly identified my board.
+
+
+
+ 2\b2.\b.4\b4.\b. G\bGe\bet\btt\bti\bin\bng\bg i\bin\bnf\bfo\bor\brm\bma\bat\bti\bio\bon\bn f\bfr\bro\bom\bm c\bco\bom\bme\bed\bdi\bi
+
+
+
+ So now that we have comedi talking to the hardware, we want to talk to
+ comedi. Here's some pretty low-level information -- it's sometimes
+ useful for debugging:
+
+
+
+ cat /proc/comedi
+
+
+
+ Right now, on my computer, this command gives:
+
+
+
+ comedi version 0.6.4
+ format string
+ 0: atmio-E at-mio-16e-10 7
+ 1: dt282x dt2821-f-8di 4
+
+
+
+ This is a feature that is not well-developed yet. Basically, it
+ currently tells you driver name, device name, and number of
+ subdevices.
+
+ In the demo/ directory, there is a command called info, which provides
+ information about each subdevice on the board. The output of it is
+ rather long, since I have 7 subdevices (4 or fewer is common for
+ other boards.) Here's part of the output of the NI board (which is on
+ /dev/comedi0.) ('demo/info /dev/comedi0')
+
+
+
+ overall info:
+ version code: 0x000604
+ driver name: atmio-E
+ board name: at-mio-16e-10
+ number of subdevices: 7
+ subdevice 0:
+ type: 1 (unknown)
+ number of channels: 16
+ max data value: 4095
+
+
+ ...
+
+
+ The overall info gives information about the device -- basically the
+ same information as /proc/comedi.
+
+ This board has 7 subdevices. Devices are separated into subdevices
+ that each have a distinct purpose -- e.g., analog input, analog
+ output, digital input/output. This board also has an EEPROM and
+ calibration DACs that are also subdevices.
+
+ Subdevice 0 is the analog input subdevice. You would have known this
+ from the 'type: 1 (unknown)' line, if I've updated demo/info recently,
+ because it would say 'type: 1 (analog input)' instead. The other
+ lines should be self-explanitory. Comedi has more information about
+ the device, but demo/info doesn't currently display this.
+
+
+
+ 3\b3.\b. I\bIn\bnd\bdi\biv\bvi\bid\bdu\bua\bal\bl d\bdr\bri\biv\bve\ber\brs\bs
+
+
+ This section contains information that is specific to each hardware
+ driver. The most current information about a driver is included in
+ the comedi source.
+
+
+ 3\b3.\b.1\b1.\b. N\bNa\bat\bti\bio\bon\bna\bal\bl I\bIn\bns\bst\btr\bru\bum\bme\ben\bnt\bts\bs A\bAT\bT-\b-M\bMI\bIO\bO E\bE s\bse\ber\bri\bie\bes\bs
+
+
+
+ 3\b3.\b.2\b2.\b. D\bDa\bat\bta\ba T\bTr\bra\ban\bns\bsl\bla\bat\bti\bio\bon\bn
+
+
+
+ 4\b4.\b. W\bWr\bri\bit\bti\bin\bng\bg p\bpr\bro\bog\bgr\bra\bam\bms\bs t\bth\bha\bat\bt u\bus\bse\be c\bco\bom\bme\bed\bdi\bi a\ban\bnd\bd c\bco\bom\bme\bed\bdi\bil\bli\bib\bb
+
+
+
+ 4\b4.\b.1\b1.\b. Y\bYo\bou\bur\br f\bfi\bir\brs\bst\bt c\bco\bom\bme\bed\bdi\bi p\bpr\bro\bog\bgr\bra\bam\bm
+
+
+ This example requires a card that has analog or digital input. Right
+ to the source:
+
+
+
+ #include <stdio.h> /* for printf() */
+ #include <comedilib.h>
+
+ int subdev = 0; /* change this to your input subdevice */
+ int chan = 0; /* change this to your channel */
+ int range = 0; /* more on this later */
+ int aref = AREF_GROUND; /* more on this later */
+
+ int main(int argc,char *argv[])
+ {
+ comedi_t *it;
+ int chan=0;
+ lsampl_t data;
+
+ it=comedi_open("/dev/comedi0");
+
+ comedi_data_read(it,subdev,chan,range,aref,XXX data);
+
+ printf("%d\n",data);
+
+ return 0;
+ }
+
+
+
+ Should be understandable. Open the device, get the data, print it
+ out. This is basically the guts of demo/inp.c, without error checking
+ or fancy options. Compile it using
+
+
+
+ cc tut1.c -lcomedi -o tut1
+
+
+
+ A few notes: The range variable tells comedi which gain to use when
+ measuring an analog voltage. Since we don't know (yet) which numbers
+ are valid, or what each means, we'll use 0, because it won't cause
+ errors. Likewise with aref, which determines the analog reference
+ used.
+
+
+
+ 4\b4.\b.2\b2.\b. C\bCo\bon\bnv\bve\ber\brt\bti\bin\bng\bg s\bsa\bam\bmp\bpl\ble\bes\bs t\bto\bo v\bvo\bol\blt\bta\bag\bge\bes\bs
+
+
+ If you selected an analog input subdevice, you should notice that the
+ output of tut1 is a number between 0 and 4095, or 0 and 65535,
+ depending on the number of bits in the A/D converter. Comedi samples
+ are a\bal\blw\bwa\bay\bys\bs unsigned, with 0 representing the lowest voltage of the
+ ADC, and 4095 the highest. Comedi compensates for anything else the
+ manual for your device says. However, you probably prefer to have
+ this number translated to a voltage. Naturally, as a good programmer,
+ your first question is: "How do I do this in a device-independent
+ manner?"
+
+ Most devices give you a choice of gain and unipolar/bipolar input, and
+ Comedi allows you to select which of these to use. This parameter is
+ called the "range parameter", since it specifies the "input range" for
+ analog input (or "output range" analog output.) The range parameter
+ represents both the gain and the unipolar/bipolar aspects.
+
+ Comedi keeps the number of available ranges and the largest sample
+ value for each subdevice/channel combination. (Some devices allow
+ different input/output ranges for different channels in a subdevice.)
+
+ The largest sample value can be found using the function:
+
+ comedi_get_maxdata()
+
+ The number of available ranges can be found using the function:
+
+ comedi_get_n_ranges()
+
+ For each value of the range parameter for a particular
+ subdevice/channel, you can get range information using the function:
+
+ ptr=comedi_get_range(comedi_file,subdevice,channel, range)
+
+ which returns a pointer to a comedi_range structure. The comedi_range
+ structure looks like
+
+
+
+ typedef struct{
+ double min;
+ double max;
+ unsigned int unit;
+ }comedi_range;
+
+
+
+ The structure element 'min' represents the voltage corresponding to
+ comedi_data_read() returning 0, and 'max' represents
+ comedi_data_read() returning 'maxdata', (i.e., 4095 for 12 bit A/C
+ converters, 65535 for 16 bit, or, 1 for digital input -- more on this
+ in a bit.) The max refer to voltage, current, etc.
+
+ "Could it get easier?", you say. Well, yes. Use the function
+ comedi_to_phys(), which converts data values to physical units. Call
+ it using something like
+
+
+
+ volts=comedi_to_phys(it,data,range,maxdata);
+
+
+ and the opposite
+
+
+
+ data=comedi_from_phys(it,volts,range,maxdata);
+
+
+
+ 4\b4.\b.3\b3.\b. A\bAn\bno\bot\bth\bhe\ber\br s\bse\bec\bct\bti\bio\bon\bn
+
+
+
+ In addition to providing low level routines for data access, the
+ comedi library provides higher-level access, much like the standard C
+ library provides fopen(), etc. as a high-level (and portable)
+ alternative to the direct UNIX system calls open(), etc. Similarily
+ to fopen(), we have comedi_open():
+
+
+
+ file=comedi_open("/dev/comedi0");
+
+
+
+ where file is of type (comedi_t *). This function calls open(), like
+ we did explicitly in a previous section, but also fills the comedi_t
+ structure with lots of goodies -- information that we will need to use
+ soon.
+
+ Specifically, we needed to know maxdata for a specific
+ subdevice/channel. How about:
+
+
+
+ maxdata=comedi_get_maxdata(file,subdevice,channel);
+
+
+
+ Wow. How easy. And the range type?
+
+
+
+ range_type=comedi_get_rangetype(file,subdevice,channel);
+
+
+
+ Cool. Other information you need to know about a channel can be
+ gotten in a similar way.
+
+
+
+ 4\b4.\b.4\b4.\b. Y\bYo\bou\bur\br s\bse\bec\bco\bon\bnd\bd c\bco\bom\bme\bed\bdi\bi p\bpr\bro\bog\bgr\bra\bam\bm
+
+
+
+ Actually, this is the first comedi program again, just that we've
+ added what we've learned.
+ #include <stdio.h> /* for printf() */
+ #include <comedi.h> /* also included by comedilib.h */
+ #include <comedilib.h> /* for comedi_get() */
+
+ int subdev = 0; /* change this to your input subdevice */
+ int chan = 0; /* change this to your channel */
+ int range = 0; /* more on this later */
+ int aref = 0; /* more on this later */
+
+ int main(int argc,char *argv[])
+ {
+ comedi_t *cf;
+ int chan=0;
+ lsampl_t data;
+ int maxdata,rangetype;
+ double volts;
+
+ cf=comedi_open("/dev/comedi0");
+
+ maxdata=comedi_get_maxdata(cf,subdev,chan);
+
+ rangetype=comedi_get_rangetype(cf,subdev,chan);
+
+ comedi_data_read(cf->fd,subdev,chan,range,aref,XXX data);
+
+ volts=comedi_to_phys(data,rangetype,range,maxdata);
+
+ printf("%d %g\n",data,volts);
+
+ return 0;
+ }
+
+
+
+ 5\b5.\b. A\bAp\bpp\bpl\bli\bic\bca\bat\bti\bio\bon\bn-\b-s\bsp\bpe\bec\bci\bif\bfi\bic\bc f\bfu\bun\bnc\bct\bti\bio\bon\bns\bs
+
+
+
+ 5\b5.\b.1\b1.\b. D\bDi\big\bgi\bit\bta\bal\bl I\bIn\bnp\bpu\but\bt/\b/O\bOu\but\btp\bpu\but\bt
+
+
+ Many boards supported by comedi have digital input and output
+ channels. Some boards allow the direction of a channel to be
+ specified in software.
+
+ Comedi groups digital channels into subdevice, which is a group of
+ digital channels that have the same characteristics. For example,
+ digital output lines will be grouped into a digital output subdevice,
+ bidirectional digital lines will be grouped into a digital I/O
+ subdevice. Thus, there can be multiple digital subdevices on a
+ particular board.
+
+ Individual digital lines can be read and written using the functions
+
+ comedi_dio_read(device,subdevice,channel,unsigned int *bit);
+ comedi_dio_write(device,subdevice,channel,unsigned int bit);
+
+ The direction of bidirectional lines can be configured using the
+ function
+
+ comedi_dio_config(device,subdevice,channel,unsigned int dir);
+
+ The parameter dir should be either COMEDI_INPUT or COMEDI_OUTPUT.
+ Many digital I/O subdevices group channels into blocks for configuring
+ direction. Changing one channel in a block changes the entire block.
+
+ Multiple channels can be read and written simultaneously using the
+ function
+
+ comedi_dio_bitfield(device,subdevice,unsigned int write_mask,unsigned
+ int *bits);
+
+ Each channel is assigned to a bit in the write_mask and bits bitfield.
+ If a bit in write_mask is set, the corresponding bit in *bits will be
+ written to the corresponding digital output line. Each digital line
+ is then read and placed into *bits. The value of bits in *bits
+ corresponding to digital output lines is undefined and device-
+ specific. Channel 0 is the least significant bit in the bitfield;
+ channel 31 is the most significant bit. Channels higher than 31
+ cannot be accessed using this method.
+
+
+
+ 5\b5.\b.2\b2.\b. S\bSl\blo\bow\bwl\bly\by-\b-v\bva\bar\bry\byi\bin\bng\bg i\bin\bnp\bpu\but\bts\bs
+
+
+
+ Sometimes, your input channels change slowly enough that you are able
+ to average many sucessive 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). Obviously, there are limitations to this:
+
+
+
+ +\bo you are ultimately limited by "spurious free dynamic range"
+
+ +\bo you need to have _some_ noise on the input channel, otherwise you
+ will be averaging the same number N times.
+
+ +\bo the more noise you have, the greater your SFDR, but it takes many
+ more samples to compensate for the increased noise
+
+ +\bo if you feel the need to average samples for 2 seconds, your signal
+ will need to be _very_ slowly-varying, i.e., not varying more than
+ your target uncertainty for the entire 2 seconds.
+
+ As you might have guessed, the comedi library has functions to help
+ you in your quest to accurately measure slowly varying inputs. I use
+ these functions to measure thermocouple voltages -- actually, the
+ library functions came from a section of code that was previously part
+ of the thermocouple reading program.
+
+ The comedi self-calibration utility also uses these functions. On
+ some hardware, it is possible to tell it to measure an internal stable
+ voltage reference, which is typically going to be very slowly varying
+ -- on the kilosecond time scale or more. So it is reasonable to
+ measure millions of samples, to get a very accurate measurement of the
+ A/D converter output value that corresponds to the voltage reference.
+ Sometimes, however, this is overkill, since there is no need to
+ perform a part-per-million calibration to a standard that is only
+ accurate to part-per-thousand.
+
+
+
+ 5\b5.\b.3\b3.\b. C\bCo\bom\bmm\bma\ban\bnd\bds\bs
+
+
+
+ Many data acquisition devices have the capability to directly control
+ acquisition using either an on-board timer or an external triggering
+ input. Comedi commands are used to control this kind of acquisition.
+ The ``comedi_cmd'' structure is used to control acquisition and query
+ the capabilities of a device (see also ``comedi_command()'',
+ ``comedi_command_test()'', and ``comedi_get_cmd_src_mask()'').
+
+ Commands specify a particular data acquisition sequence, which is
+ comprised of a number of scans. Each scan is comprised of a number of
+ conversions, which usually corresponds to a single A/D or D/A
+ conversion. The start and end of the sequence, and the start and end
+ of each scan, and each conversion is called an event.
+
+ Each of these 5 types of events are caused by a triggering source,
+ specified through the *_src members of the ``comedi_cmd'' structure.
+ The source types are:
+
+
+ +\bo TRIG_NONE: don't ever cause an event, sometimes used as a
+ stop_src.
+
+ +\bo TRIG_NOW: cause event to occur immediately, the most common
+ start_src. It is also used sometimes as a convert_src for 'burst
+ mode' aquisition where the individual channels in a scan are
+ scanned through as quickly as possible.
+
+ +\bo TRIG_FOLLOW: see notes below, usually used as a scan_begin_src.
+
+ +\bo TRIG_TIME: cause event to occur at a particular time
+
+ +\bo TRIG_TIMER: cause event to occur repeatedly at a specific rate,
+ often used as a scan_begin_src or convert_src.
+
+ +\bo TRIG_COUNT: cause event when count reaches specific value,
+ almost always used as the scan_end_src and often for stop_src.
+
+ +\bo TRIG_EXT: external signal causes event, used as start_src for
+ externally triggered conversions, and as scan_begin_src or
+ convert_src for externally paced conversions.
+
+ +\bo TRIG_INT: internal signal causes event, will probably be used
+ as start_src for output commands in the future.
+
+ For every trigger, there is a corresponding argument (the *_arg
+ members of the ``comedi_cmd'' structure) whose meaning depends on the
+ type of trigger. The meanings of the arguments are as follows:
+
+
+ +\bo trigger src = TRIG_NONE: argument has no meaning
+
+ +\bo trigger src = TRIG_NOW: argument is the delay in nanoseconds before
+ triggering
+
+ +\bo trigger src = TRIG_FOLLOW: argument has no meaning
+
+ +\bo trigger src = TRIG_TIME: argument is the time at which to trigger
+ (in what units??), but no drivers support this yet.
+
+ +\bo trigger src = TRIG_TIMER: argument is the period in nanoseconds
+ between triggers
+
+
+ +\bo trigger src = TRIG_COUNT: argument is the number of 'counts' per
+ trigger. For comedi_cmd.stop_arg, this is the number of scans to
+ perform before ending aquisition. For comedi_cmd.scan_end_arg,
+ this is the number of conversions to perform per scan.
+
+ +\bo trigger src = TRIG_EXT: argument is the digital input channel to
+ trigger on.
+
+ +\bo trigger src = TRIG_INT: argument meaning is unknown??
+
+ Not all triggers are applicable to all events. Supported triggers for
+ specific events depends significantly on your particular device.
+
+ TRIG_FOLLOW is a special type of trigger for scan_begin events that
+ triggers on the next lower level trigger, in this case, the trigger
+ for convert events. It may or may not be supported. Later, it may
+ also be used for start events if you want to chain multiple commands.
+
+ The chanlist member of the ``comedi_cmd'' structure should point to an
+ array whose number of elements is specificed by chanlist_len (this
+ will generally be the same as the scan_end_arg). The chanlist
+ specifies the sequence of channels and gains (and analog references)
+ that should be stepped through for each scan. The elements of the
+ chanlist array should be initialized by packing the channel, range and
+ reference information together with the ``CR_PACK(channel, range,
+ aref)'' macro.
+
+ The final member of the ``comedi_cmd'' structure is 'flags'. The
+ following flags are valid, and can be bitwise-or'd together.
+
+
+ +\bo TRIG_BOGUS: do the motions??
+
+ +\bo TRIG_DITHER: enable dithering??
+
+ +\bo TRIG_DEGLITCH: enable deglitching??
+
+ +\bo TRIG_RT: ask driver to use a hard real-time interrupt
+ handler. This will reduce latency in handling interrupts from your
+ data aquisition hardware. It can be useful if you are sampling at
+ high frequency, or if your hardware has a small onboard fifo. You
+ must have a real-time kernel (RTAI or RTLinux) and must compile
+ comedi with real-time support or this flag will do nothing.
+
+ +\bo TRIG_CONFIG: perform configuration, not triggering.
+
+ +\bo TRIG_WAKE_EOS: some drivers will change their behaviour when this
+ flag is set, trying to transfer data at the end of every scan
+ (instead of, for example, passing data in chunks whenever the
+ board's onboard fifo is half full). This flag may degrade a
+ driver's performance at higher frequencies.
+
+ +\bo TRIG_WRITE: write to bidirectional devices. Could be useful in
+ principle, if someone wrote a driver that supported commands for a
+ digital i/o device that could do either input or output.
+
+ There are also a few flags that indicate how timing arguments
+ should be rounded if the hardware cannot achieve the exact timing
+ requested.
+
+ +\bo TRIG_ROUND_NEAREST: round to nearest supported timing period, the
+ default.
+
+ +\bo TRIG_ROUND_DOWN: round period down.
+
+
+ +\bo TRIG_ROUND_UP: round period up.
+
+ +\bo TRIG_ROUND_UP_NEXT: this one doesn't do anything, and I don't know
+ what it was intended to do??
+
+
+
+ 6\b6.\b. L\bLi\bib\bbc\bco\bom\bme\bed\bdi\bi R\bRe\bef\bfe\ber\bre\ben\bnc\bce\be
+
+
+
+ 6\b6.\b.1\b1.\b. C\bCo\bon\bns\bst\bta\ban\bnt\bts\bs a\ban\bnd\bd M\bMa\bac\bcr\bro\bos\bs
+
+
+
+ 6\b6.\b.1\b1.\b.1\b1.\b. C\bCR\bR_\b_P\bPA\bAC\bCK\bK(\b(c\bch\bha\ban\bnn\bne\bel\bl,\b, r\bra\ban\bng\bge\be,\b, a\bar\bre\bef\bf)\b)
+
+
+ undocumented
+
+
+ 6\b6.\b.1\b1.\b.2\b2.\b. R\bRA\bAN\bNG\bGE\bE_\b_L\bLE\bEN\bNG\bGT\bTH\bH(\b()\b) (\b(d\bde\bep\bpr\bre\bec\bca\bat\bte\bed\bd)\b)
+
+
+ RANGE_LENGTH(rangetype)
+
+
+ Rangetype values are library-internal tokens that represent an array
+ of range information structures. These numbers are primarily used for
+ communication between the kernel and library.
+
+
+ The RANGE_LENGTH() macro returns the length of the array that is
+ specified by the rangetype token.
+
+
+ The RANGE_LENGTH() macro is deprecated, and should not be used in new
+ applications. It is scheduled to be removed from the header file at
+ version 1.0. Binary compatibility may be broken for version 1.1.
+
+
+
+ 6\b6.\b.2\b2.\b. D\bDa\bat\bta\ba T\bTy\byp\bpe\bes\bs a\ban\bnd\bd S\bSt\btr\bru\buc\bct\btu\bur\bre\bes\bs
+
+
+ 6\b6.\b.2\b2.\b.1\b1.\b. c\bco\bom\bme\bed\bdi\bi_\b_t\bt
+
+ The data type comedi_t is used to represent an open Comedi device. A
+ valid comedi_t pointer is returned by a successful call to
+ comedi_open(), and should be used for subsequent access to the device.
+ It is a transparent type, and pointers to type comedi_t should not be
+ dereferenced by the application.
+
+
+
+ 6\b6.\b.2\b2.\b.2\b2.\b. s\bsa\bam\bmp\bpl\bl_\b_t\bt
+
+ The data type sampl_t is one of the generic types used to represent
+ data values in libcomedi. It is used in a few places where a shorter
+ data type is useful, but is limited to 16 bits on the i386
+ architecture.
+
+ 6\b6.\b.2\b2.\b.3\b3.\b. l\bls\bsa\bam\bmp\bpl\bl_\b_t\bt
+
+ The data type lsampl_t is one of the generic types used to represent
+ data values in libcomedi. It is currently defined to be unsigned int.
+
+
+
+ 6\b6.\b.2\b2.\b.4\b4.\b. c\bco\bom\bme\bed\bdi\bi_\b_t\btr\bri\big\bg_\b_s\bst\btr\bru\buc\bct\bt (\b(d\bde\bep\bpr\bre\bec\bca\bat\bte\bed\bd)\b)
+
+
+ The comedi_trig structure
+
+
+
+ struct comedi_trig_struct{
+ unsigned int subdev; /* subdevice */
+ unsigned int mode; /* mode */
+ unsigned int flags;
+ unsigned int n_chan; /* number of channels */
+ unsigned int *chanlist; /* channel/range list */
+ sampl_t *data; /* data list, size depends on subd flags */
+ unsigned int n; /* number of scans */
+ unsigned int trigsrc;
+ unsigned int trigvar;
+ unsigned int trigvar1;
+ unsigned int data_len;
+ unsigned int unused[3];
+ }
+
+
+
+ The comedi_trig structure is a control structure used by the
+ COMEDI_TRIG ioctl, an older method of communicating instructions to
+ the driver and hardware. Use of comedi_trig is deprecated, and should
+ not be used in new applications.
+
+
+ This structure is defined as part of the Comedi kernel interface.
+
+
+
+ 6\b6.\b.2\b2.\b.5\b5.\b. c\bco\bom\bme\bed\bdi\bi_\b_s\bsv\bv_\b_t\bt
+
+
+
+ struct comedi_sv_struct{
+ comedi_t *dev;
+ unsigned int subdevice;
+ unsigned int chan;
+
+ /* range policy */
+ int range;
+ int aref;
+
+ /* number of measurements to average (for ai) */
+ int n;
+
+ lsampl_t maxdata;
+ }
+
+
+ The comedi_sv_t structure is used by the comedi_sv_*() functions to
+ provide a simple method of accurately measuring slowly varying inputs.
+ See the relevant section for more details.
+
+
+
+ 6\b6.\b.2\b2.\b.6\b6.\b. c\bco\bom\bme\bed\bdi\bi_\b_c\bcm\bmd\bd
+
+
+ undocumented
+
+
+ Related functions are described in section XXX.
+
+
+ This structure is defined as part of the Comedi kernel interface.
+
+
+
+ 6\b6.\b.2\b2.\b.7\b7.\b. c\bco\bom\bme\bed\bdi\bi_\b_i\bin\bns\bsn\bn
+
+
+ undocumented
+
+
+ Related functions are described in section XXX.
+
+
+ This structure is defined as part of the Comedi kernel interface.
+
+
+
+ 6\b6.\b.2\b2.\b.8\b8.\b. c\bco\bom\bme\bed\bdi\bi_\b_r\bra\ban\bng\bge\be
+
+
+ undocumented
+
+
+
+ 6\b6.\b.3\b3.\b. F\bFu\bun\bnc\bct\bti\bio\bon\bns\bs
+
+
+
+ 6\b6.\b.3\b3.\b.1\b1.\b. c\bco\bom\bme\bed\bdi\bi_\b_c\bcl\blo\bos\bse\be(\b()\b)
+
+
+ void comedi_close(comedi_t *it);
+
+
+ Closes a device previously opened by comedi_open().
+
+
+ The return type of this function will change to int, in order to match
+ fclose.
+
+
+ Source: /lib/comedi.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b2.\b. c\bco\bom\bme\bed\bdi\bi_\b_c\bco\bom\bmm\bma\ban\bnd\bd(\b()\b)
+
+
+ int comedi_command(comedi_t *it, comedi_cmd *cmd);
+
+ undocumented
+
+ Source: /lib/comedi.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b3.\b. c\bco\bom\bme\bed\bdi\bi_\b_c\bco\bom\bmm\bma\ban\bnd\bd_\b_t\bte\bes\bst\bt(\b()\b)
+
+
+ int comedi_command_test(comedi_t *it, comedi_cmd *cmd);
+
+ undocumented
+
+ Source: /lib/comedi.c
+
+
+
+ 6\b6.\b.3\b3.\b.4\b4.\b. c\bco\bom\bme\bed\bdi\bi_\b_d\bda\bat\bta\ba_\b_r\bre\bea\bad\bd(\b()\b)
+
+
+ int comedi_data_read(comedi_t *it,unsigned int subd,unsigned int chan,
+ unsigned int range,unsigned int aref,lsampl_t *data);
+
+
+ Reads a single sample on the channel that is specified by the comedi
+ device it, the subdevice subd, and the channel chan. For the A/D
+ conversion (if appropriate), the device is configured to use range
+ specification range and (if appropriate) analog reference type aref.
+ Analog reference types that are not supported by the device are
+ silently ignored.
+
+
+ comedi_data_read() reads one data value from the specified channel and
+ places the data value that is read in the location pointed to by data.
+
+
+ On sucess, comedi_data_read() returns 0. If there is an error, -1 is
+ returned.
+
+
+ Valid analog reference numbers are:
+
+
+ +\bo AREF_GROUND Reference to analog ground
+
+ +\bo AREF_COMMON Reference to analog common
+
+ +\bo AREF_DIFF Differential reference
+
+ +\bo AREF_OTHER Board-specific meaning
+
+ Valid data values returned by these function is an unsigned integer
+ less than or equal to maxdata, which is channel-dependent. Conversion
+ of these data value to physical units can be performed by
+ ``comedi_to_phys()''.
+
+ Source: /lib/data.c
+
+
+
+ 6\b6.\b.3\b3.\b.5\b5.\b. c\bco\bom\bme\bed\bdi\bi_\b_d\bda\bat\bta\ba_\b_w\bwr\bri\bit\bte\be(\b()\b)
+
+
+ int comedi_data_write(comedi_t *it,unsigned int subd,unsigned int
+ chan, unsigned int range,unsigned int aref,lsampl_t data);
+
+
+ Writes a single sample on the channel that is specified by the comedi
+ device it, the subdevice subd, and the channel chan. For the D/A
+ conversion (if appropriate), the device is configured to use range
+ specification range and (if appropriate) analog reference type aref.
+ Analog reference types that are not supported by the device are
+ silently ignored.
+
+ comedi_data_write() writes the data value specified by the argument
+ data to the specified channel.
+
+ On sucess, comedi_data_write() returns 0. If there is an error, -1 is
+ returned.
+
+ Valid analog reference numbers are:
+
+
+ +\bo AREF_GROUND Reference to analog ground
+
+ +\bo AREF_COMMON Reference to analog common
+
+ +\bo AREF_DIFF Differential reference
+
+ +\bo AREF_OTHER Board-specific meaning
+
+ Valid data values used by these functions is an unsigned integer less
+ than or equal to maxdata, which is channel-dependent. Conversion of
+ physical units to these data value can be performed by
+ ``comedi_from_phys()''.
+
+ Source: /lib/data.c
+
+
+
+ 6\b6.\b.3\b3.\b.6\b6.\b. c\bco\bom\bme\bed\bdi\bi_\b_d\bdi\bio\bo_\b_b\bbi\bit\btf\bfi\bie\bel\bld\bd(\b()\b);\b;
+
+ int comedi_dio_bitfield(comedi_t *it,unsigned int subd,unsigned int
+ write_mask,unsigned int *bits);
+
+
+ The function comedi_dio_bitfield() allows multiple channels to be read
+ simultaneously from a digital input or digital I/O device. The
+ parameter write_mask and the value pointed to by bits are interpreted
+ as bit fields, with the least significant bit representing channel 0.
+ For each bit in write_mask that is set, the cooresponding bit in *bits
+ is written to the digital output channel. Each digital input channel
+ is read, and the result placed in the approprate bits in *bits.
+
+
+ The current implementation reads and writes bits using separate system
+ calls, which is not ideal. When the kernel driver supports
+ simultaneous reading/writing, this will be fixed in the library.
+
+
+ It should be noted that it is not possible to access channels greater
+ than 31 using this function.
+
+
+
+ Source: /lib/dio.c
+
+
+
+ 6\b6.\b.3\b3.\b.7\b7.\b. c\bco\bom\bme\bed\bdi\bi_\b_d\bdi\bio\bo_\b_c\bco\bon\bnf\bfi\big\bg(\b()\b)
+
+ int comedi_dio_config(comedi_t *it,unsigned int subd,unsigned int
+ chan,unsigned int dir);
+
+
+ The function comedi_dio_config configures individual channels in a
+ digital I/O subdevice to be either input or output, depending on the
+ value of parameter dir. Depending on the capabilities of the hardware
+ device, multiple channels may be affected by a single call to
+ comedi_dio_config.
+
+
+ Valid directions are:
+
+ +\bo COMEDI_INPUT
+
+ +\bo COMEDI_OUTPUT
+
+ Source: /lib/dio.c
+
+
+
+ 6\b6.\b.3\b3.\b.8\b8.\b. c\bco\bom\bme\bed\bdi\bi_\b_d\bdi\bio\bo_\b_r\bre\bea\bad\bd(\b()\b)
+
+ int comedi_dio_read(comedi_t *it,unsigned int subd,unsigned int
+ chan,unsigned int *bit);
+
+
+ The function reads the status of channel chan belonging to the digital
+ input subdevice subd of device it. The result, 0 or 1, is stored in
+ bit. Returns -1 on failure.
+
+
+ This function is equivalent to comedi_data_read(it,subd,chan,0,0,bit).
+
+
+ Source: /lib/dio.c
+
+
+
+ 6\b6.\b.3\b3.\b.9\b9.\b. c\bco\bom\bme\bed\bdi\bi_\b_d\bdi\bio\bo_\b_w\bwr\bri\bit\bte\be(\b()\b)
+
+ int comedi_dio_write(comedi_t *it,unsigned int subd,unsigned int
+ chan,unsigned int bit);
+
+
+ The function writes the value of bit, 0 or 1, to channel chan,
+ belonging to the digital output device subd of device it. Returns -1
+ on failure.
+
+
+ Source: /lib/dio.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b10\b0.\b. c\bco\bom\bme\bed\bdi\bi_\b_f\bfi\bil\ble\ben\bno\bo(\b()\b)
+
+
+
+ int comedi_fileno(comedi_t *it);
+
+
+ The function comedi_fileno returns the integer descriptor for the
+ handle it. It is equivalent to the standard function fileno. If it
+ is an invalid comedi_t pointer, the function returns -1 and sets the
+ appropriate libcomedi error value.
+
+ Source: /lib/comedi.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b11\b1.\b. c\bco\bom\bme\bed\bdi\bi_\b_f\bfi\bin\bnd\bd_\b_r\bra\ban\bng\bge\be(\b()\b)
+
+
+ int comedi_find_range(comedi_t *it, unsigned int subdevice, unsigned
+ int chan, unsigned int unit, double min, double max);
+
+
+ The function comedi_find_range tries to locate the optimal (smallest)
+ range for the channel chan belonging to a subdevice of the comedi
+ device it, that includes both min and max in units. If it finds a
+ matching range, it returns its index. If no matching range is
+ available, it returns -1.
+
+
+ Valid units are:
+
+
+ +\bo UNIT_volt
+
+ +\bo UNIT_mA
+
+ +\bo UNIT_none
+
+ Source: /lib/range.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b12\b2.\b. c\bco\bom\bme\bed\bdi\bi_\b_e\ber\brr\brn\bno\bo(\b()\b)
+
+ int comedi_errno(void);
+
+
+ The function comedi_errno() returns an integer describing the most
+ recent comedilib error. This integer may be used as the errnum
+ parameter for ``comedi_strerror()''.
+
+ When a libcomedi function fails, it usually returns -1 or NULL,
+ depending on the return type. An internal library variable stores an
+ error number, which can be retrieved with comedi_errno(). This error
+ number can be converted to a human-readable form by the functions
+ ``comedi_perror()'' and ``comedi_strerror()''.
+
+ These functions are intended to mimic the behavior of the standard C
+ library functions perror(), strerror, and errno(). In particular,
+ libcomedi functions sometimes return an error that is generated by the
+ C library; the Comedi error message in this case is the same as the C
+ library.
+
+ Source: /lib/error.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b13\b3.\b. c\bco\bom\bme\bed\bdi\bi_\b_f\bfi\bin\bnd\bd_\b_s\bsu\bub\bbd\bde\bev\bvi\bic\bce\be_\b_b\bby\by_\b_t\bty\byp\bpe\be(\b()\b)
+
+
+ int comedi_find_subdevice_by_type(comedi_t *it,int type,unsigned int
+ start_subdevice);
+
+
+ The function comedi_find_subdevice_by_type tries to locate a subdevice
+ belonging to comedi device it, having type type, starting with the
+ subdevice start_subdevice. If it finds the requested subdevice, it
+ returns its index. If it does not locate the requested subdevice, it
+ returns -1 and sets the comedi error number to "subdevice not found".
+ If there is an error, the function returns -1 and sets the appropriate
+ error.
+
+
+ For subdevice types, see the manual page for the function
+ ``comedi_get_subdevice_type()''.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b14\b4.\b. c\bco\bom\bme\bed\bdi\bi_\b_f\bfr\bro\bom\bm_\b_p\bph\bhy\bys\bs(\b()\b)
+
+
+ lsampl_t comedi_from_phys(double data, comedi_range *rng, lsampl_t
+ maxdata);
+
+ Converts data given in physical units (data) into sample values
+ (lsampl_t, between 0 and maxdata). The parameter rng represents the
+ conversion information to use, and the parameter maxdata represents
+ the maximum possible data value for the channel that the data will be
+ written to.
+
+
+ Source: /lib/range.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b15\b5.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_b\bbo\boa\bar\brd\bd_\b_n\bna\bam\bme\be(\b()\b)
+
+
+ char *comedi_get_board_name(comedi_t *it);
+
+ The function comedi_get_board_name returns a pointer to a string
+ containing the name of the device. This pointer is valid until the
+ comedi descriptor it is closed. This function returns NULL if there
+ is an error.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b16\b6.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_c\bcm\bmd\bd_\b_s\bsr\brc\bc_\b_m\bma\bas\bsk\bk(\b()\b)
+
+
+ int comedi_get_cmd_src_mask(comedi_t *dev, unsigned int subdevice,
+ comedi_cmd *cmd);
+
+ undocumented
+
+ Source: /lib/cmd.c
+
+ 6\b6.\b.3\b3.\b.1\b17\b7.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_d\bdr\bri\biv\bve\ber\br_\b_n\bna\bam\bme\be(\b()\b)
+
+
+ char *comedi_get_driver_name(comedi_t *it);
+
+ The function comedi_get_driver_name returns a pointer to a string
+ containing the name of the driver being used by comedi for the comedi
+ device represented by it. This pointer is valid until the comedi
+ descriptor it is closed. This function returns NULL if there is an
+ error.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b18\b8.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_m\bma\bax\bxd\bda\bat\bta\ba(\b()\b)
+
+
+ lsampl_t comedi_get_maxdata(comedi_t *it,unsigned int
+ subdevice,unsigned int chan);
+
+
+ The function comedi_get_maxdata() returns the maximum valid data value
+ for channel chan of subdevice subdevice belonging to the comedi device
+ it This function returns 0 on error.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.1\b19\b9.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_n\bn_\b_c\bch\bha\ban\bnn\bne\bel\bls\bs(\b()\b)
+
+
+ int comedi_get_n_channels(comedi_t *it,unsigned int subdevice);
+
+ The function comedi_get_n_channels() returns the number of channels of
+ the subdevice belonging to the comedi device it and having index
+ subdevice. This function returns -1 on error.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b20\b0.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_n\bn_\b_r\bra\ban\bng\bge\bes\bs(\b()\b)
+
+
+ int comedi_get_n_ranges(comedi_t *it,unsigned int subdevice, unsigned
+ int chan);
+
+ The function comedi_get_n_ranges() returns the number of ranges of the
+ channel chan belonging to the subdevice of the comedi device it. This
+ function returns -1 on error.
+
+ Source: /lib/range.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b21\b1.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_n\bn_\b_s\bsu\bub\bbd\bde\bev\bvi\bic\bce\bes\bs(\b()\b)
+
+
+ int comedi_get_n_subdevices(comedi_t *it);
+
+ The function comedi_get_n_subdevices returns the number of subdevices
+ associated with the comedi descriptor it, or -1 if there is an error.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b22\b2.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_r\bra\ban\bng\bge\be(\b()\b)
+
+
+ comedi_range * comedi_get_range(comedi_t *it,unsigned int
+ subdevice,unsigned int chan,unsigned int range);
+
+ The function comedi_get_range returns a pointer to a comedi_range
+ structure that contains information that can be used to convert sample
+ values to or from physical units. The pointer is valid until the
+ comedi device it is closed. If there is an error, NULL is returned.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b23\b3.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_r\bra\ban\bng\bge\bet\bty\byp\bpe\be(\b()\b) d\bde\bep\bpr\bre\bec\bca\bat\bte\bed\bd
+
+
+ int comedi_get_rangetype(comedi_t *it,unsigned int subdevice,unsigned
+ int chan);
+
+ The function comedi_get_rangetype() returns an integer that represents
+ the number of range specifications available for a particular channel
+ chan of the subdevice subdevice, as well as a conversion table to
+ convert sample values to/from physical units.
+
+ The macro RANGE_LENGTH(rangetype) can be used to determine the number
+ of range specifications for a given range type.
+
+
+ This function is deprecated and should not be used in new code.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b24\b4.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_s\bsu\bub\bbd\bde\bev\bvi\bic\bce\be_\b_t\bty\byp\bpe\be(\b()\b)
+
+
+ int comedi_get_subdevice_type(comedi_t *it,unsigned int subdevice);
+
+ The function comedi_get_subdevice_type() returns an integer describing
+ the type of subdevice that belongs to the comedi device it and has the
+ index subdevice. The function returns -1 is there is an error.
+
+ Valid subdevice types are:
+
+
+ +\bo COMEDI_SUBD_UNUSED Subdevice has no functionality, i.e., a place-
+ holder.
+
+ +\bo COMEDI_SUBD_AI Analog input
+
+ +\bo COMEDI_SUBD_AO Analog output
+
+ +\bo COMEDI_SUBD_DI Digital input
+
+
+ +\bo COMEDI_SUBD_DO Digital output
+
+ +\bo COMEDI_SUBD_DIO Digital input/output. Channels are configurable as
+ to whether they are inputs or outputs.
+
+ +\bo COMEDI_SUBD_COUNTER Counter
+
+ +\bo COMEDI_SUBD_TIMER Timer
+
+ +\bo COMEDI_SUBD_MEMORY Memory, e.g., EEPROM or dual-ported RAM
+
+ +\bo COMEDI_SUBD_CALIB Calibration DACs
+
+ +\bo COMEDI_SUBD_PROC Processor or DSP
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b25\b5.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_t\bti\bim\bme\ber\br(\b()\b) (\b(d\bde\bep\bpr\bre\bec\bca\bat\bte\bed\bd)\b)
+
+
+ int comedi_get_timer(comedi_t *it,unsigned int subdev, double
+ freq,unsigned int *trigvar, double *actual_freq);
+
+
+ The function comedi_get_timer converts the frequency freq to a number
+ suitable to send to the driver in a comedi_trig structure. This
+ function remains for compatibility with very old versions of Comedi,
+ that converted sampling rates to timer values in the libary. This
+ conversion is now done in the kernel, and every device has the timer
+ type nanosec_timer, indicating that timer values are simply a time
+ specified in nanoseconds.
+
+
+ This function is deprecated and should not be used in new
+ applications.
+
+
+ Source: /lib/timer.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b26\b6.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_v\bve\ber\brs\bsi\bio\bon\bn_\b_c\bco\bod\bde\be(\b()\b)
+
+
+ int comedi_get_version_code(comedi_t *it);
+
+
+ The function comedi_get_version_code() returns the version code of the
+ currently running comedi module. The version code is of the form
+ 0x01072b, which is the version code for version 1.7.43.
+
+
+ This function is of limited usefulness. A typical mis-application of
+ this function is to use it to determine if a certain feature is
+ supported. If the application needs to know of the existence of a
+ particular feature, an existence test function should be written and
+ put in the libcomedi source.
+
+ Source: /lib/get.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b27\b7.\b. c\bco\bom\bme\bed\bdi\bi_\b_l\blo\bog\bgl\ble\bev\bve\bel\bl(\b()\b)
+
+
+ int comedi_loglevel(int loglevel);
+
+
+ This function affects the output of debugging and error messages from
+ libcomedi. By increasing the loglevel, additional debugging
+ information will be printed. This function returns the previous
+ loglevel. Error messages and debugging are printed to the stream
+ stderr. The loglevel can also be affected by the environment variable
+ COMEDI_LOGLEVEL.
+
+
+ In order to conserve resources, some debugging information is disabled
+ when libcomedi is compiled.
+
+
+ The meaning of the loglevels is as follows:
+
+
+ +\bo COMEDILIB_LOGLEVEL=0
+
+ Comedilib prints nothing.
+
+ +\bo COMEDILIB_LOGLEVEL=1 (default)
+
+ Comedilib only prints error messages when there is a self-
+ consistency error (i.e., internal bug).
+
+ +\bo COMEDILIB_LOGLEVEL=2
+
+ Comedilib prints an error message when an invalid parameter is
+ passed to comedilib.
+
+ +\bo COMEDILIB_LOGLEVEL=3
+
+ Comedilib prints an error message whenever an error is generated in
+ the comedilib library or is generated in the C library when called
+ by comedilib.
+
+ +\bo COMEDILIB_LOGLEVEL=4
+
+ Comedilib prints a lot of debugging messages.
+
+ Bugs: Libcomedi doesn't currently have much debugging information.
+
+ Source: /lib/error.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b28\b8.\b. c\bco\bom\bme\bed\bdi\bi_\b_o\bop\bpe\ben\bn(\b()\b)
+
+
+ comedi_t *comedi_open(char *filename);
+
+ Opens a comedi device specified by the filename filename. Returns
+ NULL on error. On sucess, it returns a handle that is given as a
+ parameter to other libcomedi functions.
+
+
+ You are not supposed to have access to the internals of the comedi_t
+ structure.
+
+ Bugs: Not strictly identical to fopen
+
+ Source: /lib/comedi.c
+
+
+
+ 6\b6.\b.3\b3.\b.2\b29\b9.\b. c\bco\bom\bme\bed\bdi\bi_\b_p\bpe\ber\brr\bro\bor\br(\b()\b)
+
+
+ void comedi_perror(const char *s);
+
+ When a comedilib function fails, it usually returns -1 or NULL,
+ depending on the return type. An internal library variable stores an
+ error number, which can be retrieved with ``comedi_errno()''. This
+ error number can be converted to a human-readable form by the
+ functions comedi_perror() and ``comedi_strerror()''.
+
+ These functions are intended to mimic the behavior of the standard C
+ library functions perror(), strerror, and errno(). In particular,
+ comedilib functions sometimes return an error that is generated inside
+ the C library; the comedi error message in this case is the same as
+ the C library.
+
+ The function comedi_perror() prints an error message to stderr. The
+ error message consists of the argument string, a colon, a space, a
+ description of the error condition, and a new line.
+
+ Bugs: Does not support internationalization.
+
+ Source: /lib/error.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b30\b0.\b. c\bco\bom\bme\bed\bdi\bi_\b_s\bst\btr\bre\ber\brr\bro\bor\br(\b()\b)
+
+
+ *comedi_strerror(int errnum);
+
+ When a comedilib function fails, it usually returns -1 or NULL,
+ depending on the return type. An internal library variable stores an
+ error number, which can be retrieved with ``comedi_errno()''. This
+ error number can be converted to a human-readable form by the
+ functions ``comedi_perror()'' and comedi_strerror().
+
+ These functions are intended to mimic the behavior of the standard C
+ library functions perror(), strerror, and errno(). In particular,
+ comedilib functions sometimes return an error that is generated inside
+ the C library; the comedi error message in this case is the same as
+ the C library.
+
+ The function comedi_strerror() returns a pointer to a character string
+ describing the comedilib error errnum. The persistence of the
+ returned pointer is undefined, and should not be trusted after the
+ next libcomedi call. An unrecognized error number will return a
+ pointer to the string "undefined error", or similar.
+
+ Bugs: Does not support internationalization.
+
+ Source: /lib/error.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b31\b1.\b. c\bco\bom\bme\bed\bdi\bi_\b_s\bsv\bv_\b_i\bin\bni\bit\bt(\b()\b)
+
+
+ int comedi_sv_init(comedi_sv_t *sv,comedi_t *dev,unsigned int subd,
+ unsigned int chan);
+
+
+ comedi_sv_init initializes the slow varying comedi structure sv of the
+ device dev, the subdevice subd (analog input) and the channel chan.
+ The slow varying comedi structure sv of type ``comedi_sv_t'' specifies
+ the signal measurement. The default number of averaged samples is
+ 100. Returns zero on success, -1 on error.
+
+ Bugs: comedi_sv_* was very poorly designed.
+
+ Source: /lib/sv.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b32\b2.\b. c\bco\bom\bme\bed\bdi\bi_\b_s\bsv\bv_\b_u\bup\bpd\bda\bat\bte\be(\b()\b)
+
+
+ int comedi_sv_update(comedi_sv_t *sv);
+
+ The function comedi_sv_update updates the slow varying comedi
+ structure sv. Returns zero on success, -1 on error.
+
+ Source: /lib/sv.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b33\b3.\b. i\bin\bnt\bt c\bco\bom\bme\bed\bdi\bi_\b_s\bsv\bv_\b_m\bme\bea\bas\bsu\bur\bre\be(\b()\b)
+
+
+ int comedi_sv_measure(comedi_sv_t *it,double *data);
+
+ comedi_sv_measure measures the slow variing signal. The measurement is
+ specified by the slow varying comedi structure sv, the result is
+ stored in data. On success returns the number of samples, -1 on
+ error.
+
+ Source: /lib/sv.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b34\b4.\b. c\bco\bom\bme\bed\bdi\bi_\b_t\bto\bo_\b_p\bph\bhy\bys\bs(\b()\b)
+
+
+ double comedi_to_phys(lsampl_t data, comedi_range *rng, lsampl_t
+ maxdata);
+
+ Converts data given in sample values (lsampl_t, between 0 and maxdata)
+ into physical units (double). The parameter rng represents the
+ conversion information to use, and the parameter maxdata represents
+ the maximum possible data value for the channel that the data was
+ read.
+
+ Source: /lib/range.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b35\b5.\b. c\bco\bom\bme\bed\bdi\bi_\b_t\btr\bri\big\bgg\bge\ber\br(\b()\b) (\b(d\bde\bep\bpr\bre\bec\bca\bat\bte\bed\bd)\b)
+
+
+ int comedi_trigger(comedi_t *it,comedi_trig *trig);
+
+ The function comedi_trigger instructs comedi to perform the command
+ specified by the ``trigger structure'' trig. Results depend on the
+ particular command being issued. If there is an error, -1 is
+ returned.
+
+ Lifetime: removal at 1.0.
+
+ Source: /lib/comedi.c
+
+
+
+ 6\b6.\b.3\b3.\b.3\b36\b6.\b. c\bco\bom\bme\bed\bdi\bi_\b_g\bge\bet\bt_\b_s\bsu\bub\bbd\bde\bev\bvi\bic\bce\be_\b_f\bfl\bla\bag\bgs\bs(\b()\b)
+
+
+ int comedi_get_subdevice_flags(comedi_t *dev, unsigned int subdevice);
+
+
+ This function returns a bitfield describing the capabilities of the
+ specified subdevice. If there is an error, -1 is returned.
+
+
+ The bits are:
+
+
+ +\bo SDF_BUSY subdevice is running a command
+
+ +\bo SDF_BUSY_OWNER subdevice is running a command started by the file
+ descriptor used by dev.
+
+ +\bo SDF_LOCKED subdevice is locked
+
+ +\bo SDF_LOCKED_OWNER subdevice is locked by the file descriptor
+ used by dev.
+
+ +\bo SDF_MAXDATA maximum data values are channel dependent
+
+ +\bo SDF_FLAGS channel flags are channel dependent
+
+ +\bo SDF_RANGETYPE range types are channel dependent
+
+ +\bo SDF_MODE0 deprecated
+
+ +\bo SDF_MODE1 deprecated
+
+ +\bo SDF_MODE2 deprecated
+
+ +\bo SDF_MODE3 deprecated
+
+ +\bo SDF_MODE4 deprecated
+
+ +\bo SDF_CMD subdevice supports commands
+
+ +\bo SDF_READABLE subdevice can be read from
+
+ +\bo SDF_WRITEABLE subdevice can be written to
+
+ +\bo SDF_RT deprecated
+
+ +\bo SDF_GROUND subdevice is capable of ground analog reference
+
+ +\bo SDF_COMMON subdevice is capable of common analog reference
+
+ +\bo SDF_DIFF subdevice is capable of differential analog
+ reference
+
+ +\bo SDF_OTHER subdevice is capable of other analog
+ reference
+
+ +\bo SDF_DITHER subdevice recognizes dither flag
+
+ +\bo SDF_DEGLITCH subdevice recognizes deglitch flag
+
+ +\bo SDF_MMAP deprecated
+
+ +\bo SDF_RUNNING subdevice is acquiring data (i.e., command has not
+ completed)
+
+ +\bo SDF_LSAMPL subdevice uses samples of type lsampl_t (otherwise
+ sampl_t)
+
+ +\bo SDF_PACKED subdevice uses bitfield samples (otherwise it uses
+ one sample per channel)
+
+
+
+ The bit definitions are part of the Comedi kernel interface.
+
+
+
+ 6\b6.\b.3\b3.\b.3\b37\b7.\b. c\bco\bom\bme\bed\bdi\bi_\b_r\bra\ban\bng\bge\be_\b_i\bis\bs_\b_c\bch\bha\ban\bn_\b_s\bsp\bpe\bec\bci\bif\bfi\bic\bc(\b()\b)
+
+
+ int comedi_range_is_chan_specific(comedi_t *dev,unsigned int
+ subdevice);
+
+
+ If each channel of the specified subdevice has a different range
+ specification, this function returns 1. Otherwise, this function
+ returns 0. On error, this function returns -1.
+
+
+
+ 6\b6.\b.3\b3.\b.3\b38\b8.\b. U\bUn\bnd\bdo\boc\bcu\bum\bme\ben\bnt\bte\bed\bd f\bfu\bun\bnc\bct\bti\bio\bon\bns\bs
+
+
+
+ +\bo comedi_maxdata_is_chan_specific()
+
+ +\bo comedi_get_buffer_size()
+
+ +\bo comedi_get_max_buffer_size()
+
+ +\bo comedi_set_buffer_size()
+
+ +\bo comedi_set_max_buffer_size()
+
+ +\bo comedi_do_insnlist()
+
+ +\bo comedi_do_insn()
+
+ +\bo comedi_lock()
+
+ +\bo comedi_unlock()
+
+ +\bo comedi_get_cmd_src_mask()
+
+ +\bo comedi_get_cmd_generic_timed()
+
+ +\bo comedi_cancel()
+
+ +\bo comedi_command()
+
+ +\bo comedi_command_test()
+
+ +\bo comedi_poll()
+
+ +\bo comedi_get_buffer_contents()
+
+ +\bo comedi_mark_buffer_read()
+
+ +\bo comedi_get_buffer_offset()
+
+ +\bo comedi_set_global_oor_behavior()
+
+
+
projects / comedilib.git / commitdiff