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.
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
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.
What you talkin about?
Amux can control by API (its easy than by resister)
Don't you know??
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
Almost forgot, using AMUXn requires at least 2 lines of code,
a Start() command and a Select() command.