scaling for sserial analog in ?

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02 Jul 2012 17:37 #21495 by cmorley
I just added code to pncconf for exposing analog in pins from the 7i64 and 7i73 cards.
I notice that there is no way to scale the input.

As this seems like a fairly common thing to do I was curious why the capability was not
built into the cards?

I was thinking that the guys who are trying to control a 3D printer could use the analog input
to detect print head temperature.

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02 Jul 2012 19:07 #21498 by PCW
Its not actually something the cards do but rather what the driver does with the card data.
the driver does allow you to scale outgoing data but not incoming data for some reason.

The card data is always scaled in natural units, ADCs and DACs normally in volts and for example the 7I88 thermocouple card will have outputs scaled in degrees C.

I guess you could use the offset component to scale/offset inputs until input scaling gets added to the driver

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02 Jul 2012 19:28 #21502 by cmorley
Thanks for explaining.
I thought the sserial card supplied the pin names?
Do you mean the hostmot2 driver does allow scaling of inputs at the moment?

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02 Jul 2012 20:32 - 02 Jul 2012 20:37 #21503 by PCW
The card supplies the pin type and name and units and default scaling information
(which the driver uses as default though the driver does not expose the units)

That is the 7I77 analog outputs have a default scale of +-10V
and this used by the driver if the scaling is not changed
The driver does allow re-scaling of outputs
but does not allow re-scaling of inputs currently


What you are talking about is not a pin but rather a parameter for
setting the input scale. The current HostMot2 driver for sserial
does not support this (and all parameters are supplied by the driver, not the card)
Last edit: 02 Jul 2012 20:37 by PCW. Reason: unfinshed

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