>> Ya i did post my real code...

If so, where is your display code ?

>> I used signed or unsigned char...

do you know the difference between signed and unsigned ?

>> adc_sum >>=4; // /16 => 8 BIT result

take a look at the given code example. Due to the loop (for) you will take 16, 8 BIT, adc samples.

adc_sum += ADC0H; short form of
adc_sum = adc_sum + ADC0H;

will add those 16 samples to adc_sum (adc_sum is declared as an integer because 8 BIT + 8 BIT is at least more then 8 BIT ;-)) and

adc_sum >>=4;

will divide it by 16 so you get the average of 16 samples and the result will fit in to 8 BIT. Hope you understand whats going on? If you simply take just one sample how do you know that this is not a peak that you measure ? therefore you should take a couple of samples and build an average.

>> and my LCD display this: {{{{{{{{

So again, where is your display code ? Without seeing your complete code its impossible to help. Watch out for ITOA.

If you are still interested in getting some help then please take your time and:

1. post your complete code
2. try to understand the given code
3. describe the steps you tryed to make the code up and running