Subject:
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Re: How to use the addition analog port ?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 28 Nov 1998 16:47:54 GMT
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Original-From:
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JDUNN@stopspamUNM.EDU
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Viewed:
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2092 times
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You can time share both your digital and your analog so long as your signal
update speeds are not critical.
Use a 4 to 8 demultiplexing chip for 4 of your digital I/O and an 8 to 4
multiplexer for the other 4. This effectively provides 8 digital inputs
and 8 digital outputs. Extra assembly language needs to be done to encode
and decode the respective signals. I'm sure there is a memory efficient
way of doing this. The increased update times should be relatively minor
depending upon the programming technique used.
For more analog I/O, take one or more of the digital outputs and switch
banks of analog signals to the analog inputs you have through solid state
relays (there are IC chips made for this purpose with 8 bi-directional
channels on a single chip). You can select each of the analog ports as
either inputs or outputs independently for each bank by associating the
setup with the particular multiplexed digital output. For signals that need
to be monitored more frequently, they can be tied in to more than one bank,
or you can sacrifice the number of analog channels and use some of your
multiplexed digital inputs for interrupts to get immediate attention.
If all of the digital I/O is used to select analog I/O, you could monitor
or transmit 2 to the 8th times 8 standard analog plus 4 SP0 analog, or 3072
mixed analog inputs/outputs. And these can be used for digital inputs as
well by doing a comparison (ie >127 is a 1) of the registers for inputs and
selecting 255 for 1 or 0 for zero for digital outputs.
Keep in mind though that the update time increases only for each bank of
analog that you setup and select. Another way of increasing your update
rate would be selecting those banks that need shorter update times more
often and conditionally looking at others.
There are other methods of bank switching analog and digital signals that
could allow hundreds of billions of I/O, but the above implementation is
relatively straight forward to understand and implement.
phillip chia wrote:
>
> Hi,
> I need additional port for the analog input. I have used up 7 analog ports
> and 9 digital ports. Hence, I need additional port from the HD. I came to
> know that there are 4 extra analog port on the HD just above the analog
> port 0 to 3. These additional ports are connected to PE0 to PE3 . HOW
> should i command these ports to receive the input signal ? Eg, if
> analog(3) <127 {........}. Then, How should I use such command for PE0 to
> PE3 to operate on the HD?
>
> Besides, Is there any way to expand the input for the usage of digital port
> since the 9 digital ports i have finished used up ?
>
> rgds,
--
James Dunn
NASA/Pursue Sensor Fusion and Mobile Navigation
jdunn@unm.edu
Chat# 14708321
Like a rose, life is sweet,
with just enough thorns
to make it interesting.
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