Hi there !!!!!
I woluld need again your help!
I am triyng to read on display module four FSR ( force sensing resistor) and they look lik NTC thermistor in relation to resistance versus physic exitation. In this case exitation is a finger tip touch.
I have multiplexed them to a ADC_DelSig_v3_09 and I have used harward multiplexer.
I have atacched a bunddled zip with the proyect.
The TIA has an output of vdd/2 when any FSR is pressed, and vout can reach 0 V depending on the strenght of the touch can be.
So the input range of my ADC is 3.3 V/2 to 0v.
The result is the four redout are 0x00008104 always , which it seems to be correct when any FSR is pressed.
But it does not work when I press any of the FSR.
I would apreciate any help
Thank you very much.
I do not think you need TIA given the resolution of the DelSig.
Just terminate the sensors to ground with a sampling R
which forms a simple divider. Plus DelSig has an input
buffer that you can take G up to 8.
One other thought, you could run DelSig in continuous mode,
attach ISR to EOC, throw away a couple of samples and use
the next. This would allow CPU to do other stuff instead of sitting
in a blocking f() waiting for A/D to finish. Or rewrite code to use
end of conversion f() to use non blocking return.
Its importent for you to do an error analysis of the sensor/divider network
and the A/D to make sure repeatability is accomplished in your product design
and you meet your design goals. Easiest way to do this is convert all errors to
LSBs and add them linearly.
Exccept noise related analysis, which has to be done in RMS.