On Fri, 11 Apr 2008, How Lin Hoo wrote:
> Date: Fri, 11 Apr 2008 06:46:07 +0000
> From: How Lin Hoo <[EMAIL PROTECTED]>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> To: emc-users@lists.sourceforge.net
> Subject: [Emc-users] Possible bug in Mesa 5I20 for polarity of DAC
>
>
> Dear all,
>
> I am currently implementing Mesa 5i20, 7i33 and 7i37 cards for my
> self-designed machine. I have a problem with regards to the polarity of the
> DACs from the Mesa 7i33 card.When I set the voltage of DAC to a value
> (example: 5V) using EMC, the DAC sent out from the 7i33 card is -5V which is
> of opposite polarity. I had rectified by using a scale function to change my
> gain to -1. However, this is not an ideal solution as other users will think
> the gain is -1.
>
> Is there anyone who has encountered the same problem? Is there is a possible
> bug in the Mesa driver? Thank you for your attention.Regards,Daniel
Its either a bug in the driver or the FPGA firmware (depending on who
you wish to blame: PeterV or PeterW) At this point its probably better to live
with the bug than have a update that will break existing configurations (in a
_really_ bad way = servo runaway).
If you can live with the -gain for a couple of months there is a new
5I20 configuration available (HostMot2) and the driver for that will have the
correct output polarity. HostMot2 also improves the 7I33 performance somewhat
because is has a selectable 12 bit PDM mode and PDM frequency selectability
(low to 100 MHz) to get the best ripple/linearity tradeoff in the 7I33.
Peter Wallace
Mesa Electronics
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