Re: comedi_rt_timer

On Wednesday 23 February 2005 09:52 am, you wrote:
> Le mercredi 23 février 2005 à 12:11 +0000, Ian Abbott a écrit :
> > On 23/02/05 08:56, Emmanuel PACAUD wrote:
> > > In comedi_rt_timer driver, start src must be TRIG_INT for analog
> > > output, and TRIG_NOW for all other emulated subdevices.
> > >
> > > And I don't understand why...
> > >
> > > Could someone with more knowledge than me about comedi explain such
> > > a limitation ?
> >
> > Using TRIG_INT allows you to write data to the device before starting
> > the acquisition.  If TRIG_NOW was used, there might not be any data
> > available for the first scan or the first conversion, in which case an
> > underrun error would be reported.
>
> Yes.
>
> > The Comedilib documentation mentions TRIG_FOLLOW as a possible
> > start_src for an output subdevice.  This says that the acquisition
> > should start when data is written to the buffer.  However, it's not
> > supported yet :-(
>
> I tried to adapt comedi_rt_timer in order to enable TRIG_FOLLOW, and it
> seems to work for me.

I don't see any tangible benefit from supporting TRIG_FOLLOW for start_src 
on output commands.  It provides no increased functionality over doing 
write then internal trigger?

-- 
Frank