Re: Analog output device support design

[Angus Gratton <angus.gratton@anu.edu.au>]

Hi Ralph & Andreas,

Sorry, I've been a bit too quiet on this thread.

On Wed, 2010-07-28 at 09:51 -0400, Ralph Lange wrote:
> Here I would like to ask Angus, if the two-step conversion is really needed.
> 
> While in some cases (Andreas was giving examples) the two-step 
> conversion might be useful and appropriate, it is *not* the regular case.
> Usually the database designer sets LINR, EGU, EGUF, and EGUL. They will 
> do that for every analog record that does linear conversion, so I would 
> not consider this an extra burden.

What I initially did for the DAC is implementing an @param which set
EGUF & EGUL by default if they weren't already set. This is what I
described in my original post, when I didn't quite know what I was
doing.

Then I looked at the results and realised having "@5V BIP" is totally
redundant given the EGUF/EGUL, as you guys have both kindly explained to
me above. So I pulled all that code out - device support is now much
slimmer and simpler, and more standard.

In case I haven't explained well enough, here's a simple test database
record for my new device support:

record(ao, "analog1")
{
		  field(DESC, "Analog out channel 0")
		  field(DTYP, "msda128")
		  field(OUT, "#C2 S0")
		  field(LINR,"LINEAR")
		  field(EGUF, 10)
		  field(EGUL, -10)
}

... for a channel jumpered +/- 10v bipolar. Nice and simple.

I'll post the device support sources & drivers somewhere publicly as
well, once they're done (just need to check with the uni first.)

Regards,

Angus