+++ /dev/null
-From owner-comedi@stm.lbl.gov Tue Jun 29 00:56:15 1999
-Received: (from majordom@localhost)
- by stm.lbl.gov (8.8.7/8.8.7) id AAA29747
- for comedi-list; Tue, 29 Jun 1999 00:56:15 -0700
-Received: (from ds@localhost)
- by stm.lbl.gov (8.8.7/8.8.7) id AAA29742;
- Tue, 29 Jun 1999 00:56:14 -0700
-Message-ID: <19990629005613.A29725@stm.lbl.gov>
-Date: Tue, 29 Jun 1999 00:56:13 -0700
-From: David Schleef <ds@stm.lbl.gov>
-To: Tomasz Motylewski <motyl@stan.chemie.unibas.ch>
-Cc: comedi@stm.lbl.gov
-Subject: Re: pcl-711 driver ISR.
-References: <Pine.LNX.3.96.990629020900.18849h-100000@crds.chemie.unibas.ch>
-Mime-Version: 1.0
-Content-Type: text/plain; charset=us-ascii
-X-Mailer: Mutt 0.91.1
-In-Reply-To: <Pine.LNX.3.96.990629020900.18849h-100000@crds.chemie.unibas.ch>; from Tomasz Motylewski on Tue, Jun 29, 1999 at 02:22:26AM +0200
-Sender: owner-comedi@stm.lbl.gov
-Precedence: bulk
-Status: RO
-Content-Length: 5035
-Lines: 143
-
-On Tue, Jun 29, 1999 at 02:22:26AM +0200, Tomasz Motylewski wrote:
->
-> Is there any documentation for _ai_mode0, 1 2 3 4 etc? Do they mean
-> the same for different cards ?
-
-Found it. It has a little extra info, but that shouldn't hurt.
-Here it is:
-
------
->
-> 1. What are the different modes? 2, 3, and 4 seem pretty well
-> explained, but I guess mode 0 is a one-shot sample, and mode is 1...
-> what?
-
-0 is one-shot. Actually, some of the drivers will return as many
-samples as you ask (i.e., trig.n), for the channels you specify. Others
-will limit it to a reasonable number that will finish in 1-10 ms, and
-the rest only return 1, for the first channel specified. The idea here
-is "at the convenience of the driver, preferably fast."
-
-mode 1 is timed acquisition, with a single timer. For example, if
-you request channels 2, 4, and 6, in mode 1, with the number of samples
-(trig.n) = 2, and a timer value that corresponds to 100 us, the driver
-programs the device to measure inputs at these times:
- time chan
- +0 us 2
- +100 us 4
- +200 6
- +300 2
- +400 4
- +500 6
-If you board can support mode 2, mode 1 is not necessary. Comedilib
-will eventually emulate it.
-
-mode 2 is similar, but has 2 timers, a major timer (trig.timeval)
-and a minor timer (trig.timeval1). Taking the previous example, but
-with a major timer of 1000 us and a minor timer of 100 us, inputs
-are measured at these times:
- time chan
- +0 us 2
- +100 us 4
- +200 6
- +1000 2
- +1100 4
- +1200 6
-
-mode 3 is like mode 1, except that an external trigger is used. If
-t(n) represents the time of the nth trigger, inputs are measured at
-the following times:
- time chan
- t(1) 2
- t(2) 4
- t(3) 6
- t(4) 2
- t(5) 4
- t(6) 6
-
-mode 4 uses an external trigger and a minor timer. With a minor
-timer of 100 us, we get:
- time chan
- t(1) 2
- t(1)+100 us 4
- t(1)+200 us 6
- t(2) 2
- t(2)+100 us 4
- t(2)+200 us 6
-
-As a bit of background, mode 2 & 4 are the most useful. Mode 1
-is the only supported by many boards. Mode 3 is the only supported
-by a few boards. Mode 3 could be useful to synchronize multiple
-boards, if the master board is capable of exporting a trigger signal.
-
-If you have an application that doesn't fit into the existing
-modes, and your board supports it, I'm content with adding more
-modes.
-
->
-> 2. How is the channel mask to be interpreted? If multiple channels are
-> specified in the mask, should successive bytes in the data array match
-> to different channels?
-
-CR_MASK() packs range, analog reference, and channel information into
-a 32-bit integer. An array of these integers are passed from the program
-to comedi, to be used as mentioned above. Samples are put into the
-data array in time order.
-
->
-> 3. If ntrig is zero, does that mean sample nothing, or keep sampling
-> forever?
-
-I haven't decided. Since comedi doesn't currently support continuous
-acquisition, I have time to decide. It did previously, but I never
-wrote buffer streaming code for the 0.6 series. It's on my list.
-The alternative to specifying continuous is ((unsigned int)(-1)).
-
->
-> 4. How should a card like mine be handled, where there's a single A/D
-> converter servicing multiple channels? Should the driver attempt to
-> multiplex everything together, and then finally return an error if a
-> request is made that just can't be squeezed in?
-
-If I understand what you are saying, yes. I.e., if in mode 2, you ask
-for 10 channels, major timer 50 us, minor timer of 10 us, then yes,
-you should return an error. In actuality, most drivers aren't that
-mature yet.
-
->
-> 5. Anything else you can send me that's useful? I've got comedi and
-> comedilib 0.7.0.
-
-Not really. I'm trying to pause comedi/comedilib development for
-a little while so I can write documentation, so maybe soon there'll
-be more info.
-
-Timer values are currently board dependent. Most boards use dividers
-off a frequency like 20 Mhz, but some have multiple clocks and/or
-prescalers. I'd like to just specify timers as (say) nanoseconds,
-and let the boards do the division, but that limits timers to ~4.29
-seconds.
-
-About ranges, range info, range types, etc.: Typical boards allow
-you to specify an input gain on the A/D converter, and possibly
-also unipolar/bipolar. Collectively, these are "input ranges". A
-board that allows 4 different gain settings, and unipolar/bipolar
-setting, would have 8 available ranges, numbered 0-7. This range
-specification is what you give to CR_PACK(). Not all boards are
-identical, so each subdevice (or channel, sometimes) has a
-range_type, to determine what voltages your range specification
-cooresponds to. The low bits of range_type give the number
-of ranges available. The high bits are used by the comedi module
-when it is asked to return an array of comedi_krange structures;
-these structures contain the max and min voltages and a unit
-specification for each range.
-
-
-
-
-dave...
-
-
-****
-Sent by the Comedi mailing list - <comedi@stm.lbl.gov> To unsubscribe,
-send mail to <comedi-request@stm.lbl.gov> with "unsubscribe" in the body.
-
projects / comedi.git / commitdiff