maybe I said it wrong... I agree what PaulS says.
What I mean is that with a short time calibration there is not enough time to fullfill the memory while reading for calibration. That's why the program then runs as a sensor reading (256 analog sensors) with no problem.
In this way two matrices have been calculated, so I guess I will be able to save them. Still to do...
anyway, there's something I still don't understand... seems that while() stores not one minVal array, but lot of them (the same with maxVal), as if I rise up to 50000 milliseconds the system crashes. And here is where I suposed alloc() could help. At this point must say that minVal (the minimal value from pressure) is a changing value ranged from 50 to 53 (depending on resistors and op-amp), so there is a practical infinite diferent matrices that can be calculated and stored.
thanks
toni