Thank you gentlemen for your replies, much appreciated ..

That's the whole thing that i've attached ( Conditioning Circuit "Amplification + Filtration ..." plus the Command Circuit "Motor + electrovalve" .. )
besides the LCD & MMC interfacing circuits ....
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i'm still working on the LCD interface with the MCU but mainly i'm going to wire :

- the "Enable" LCD pin to the pic pin 30 (RD7/PSP7)
- the "Register Select" LCD pin to pic pin 29 (RD6/PSP6)
- the LCD's Data pins (DB0,DB1,DB2, ... DB7) to the pic's (pin 33,pin34,pin35,...pin40) in order (which represent RB0 to RB7)
- and of course the Write/Read pin to the GND & the Contrast Adjustment to a Potentiometer .. .

- do you think i should do any changes to any of the circuits ?
- should i add some current limiting resistors and/or protection diodes to ADC0 & ADC1 ? if so, how can i wire the protection diodes the right way into the existing circuit ?

Thank You again for your help ..