Hello,
I am trying to use a HiTechnic SMUX to collect data from 4 sensors ( Vernier and other kinds). I would read the value from each sensor , and then save it in the datalog. I am having difficulties understanding how the multiplexer works. I have read the programming guide PDF by Xander Soldaat. Your help is appreciated! Thank you.

You should check out some of the examples for the light sensor (lego-light-SMUX-test1.c and 2). I don't support the Vernier sensors. The reasons being that they seemed to be unwilling to help me with some hardware when I approached them about it. This is what their CEO had to say to me:

The Vernier is analogue, so your best bet would be to see how the lego-light driver does its thing

= Xander

So in the code , is it reading the raw value from the sensor?Thank you.

Well, sort of. The SMUX polls the sensor and then makes that data available to the NXT. You may find that you have to do a bit of calibration as the analogue value read by the SMUX is based on 3V3 and not the 4V3 that the NXT uses. In most cases this not an issue, but with the Vernier it might be.

= Xander

Is it going to be a simple linear calibration? If I have two solutions of known values,and I take two measurements with the sensor , then I do the calibration , is that going to be enough?
Also, if I am trying to read the values from 2 sensors, would it be as simple as :
const tMUXSensor LEGOLS= msensor_S1_1;
const tMUXSensor LEGOLS1= msensor_S1_2;
raw=LSvalRaw(LEGOLS);
nxtDisplayTextLine(0,"Sensor 1: %4d",raw);
wait1Msec(1000);
raw=LSvalRaw(LEGOLS1);
nxtDisplayTextLine(0,"Sensor 1: %4d",raw);
Thank you!

That looks about right As for linear or not, that's something you'll have to find out experimentally. As I said before, I have no experience with Vernier, so I have no idea how they perform with 3V3.

= Xander