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I am developping one psoc based product. In which I have to use ins amp.
Many times i used to make offset voltage zero.
For doing this I have to connect inverting and non inverting terminals to each other (SHORT)
I want to do this in runtime
Again I want to disconnect them.
How to do do this is run time. Please explain
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PSoC 1
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Depending on where the IA is placed you would use register writes
to the analog column INV input control register. Take a look at
ACBxxCR1 in the TRM (Technical Reference Manual). This register
controls a mux, as well as other stuff, the selects where INV input
gets its signal.
Generally when you change a blocks settings you issue a STOP() to
the block, its clocks (if applicable), do the changes, and restart the block.
Regards, Dana.
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One other thought, when you tie the inputs together make sure
they are terminated in some driven voltage, eg. not floating, otherwise
you would get readings from A/D measuring offset drifting due to finite
CMR of IA.
This ap note may also be of interest, correlated double sampling for
noise rejection. http://www.cypress.com/?rID=2894 AN2226
Regards, Dana.
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Don't confuse AMUXn, which is a mux module you place/add to a design,
and the AnalogColumn_InputMUXn shown in prior post, INSAMP1.jpg.
That mux is always present, part of the HW routing resources.
The AnalogColumn_InputMUXn is controled by the register write I referred
to in my earlier post.
Regards, Dana.
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Amux can control by API (its easy than by resister)
Don't you know??
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What you showed in INSAMP1.JPG was a route, done by register, to
tie the INV input to the NINV input. That is a single register write, a one
line command, that writes a byte with specific bit settings, that controls
AnalogColumn_InputMUXn to accomplish that route.
If you used AMUXn, yes, a one line command, API, could also be used.
But that requires additional HW and its attendant API code.
So why do you think thats "easier" ? I think its pretty much same, and you
save FLASH, 25 bytes, and allow HW (AMUXn) to be used for something
else.
Regards, Dana.
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Almost forgot, using AMUXn requires at least 2 lines of code,
a Start() command and a Select() command.
Regards, Dana.