Analog input A1 can't work well


Hi there,

I want to use A0 to A5 as analog inputs and show values via my phone, but I found the value I get from A1 is always inaccurate, for example, when I want to read 0.1V by analogRead function, it shows something like 253/3FF instead of 22/3FF. The others works pretty well. Below is my code
int i;
for( i = 0; i < 5; i++)
//discard the first data
ph_voltage[i] = analogRead(A0+i);
ph_voltage[i] = analogRead(A0+i);

Thanks so much for your help.