hi
i hope i'm not adressing an issue that has been discussed thoroughly already -- so far i haven't found anything yet.
what i'm trying to do is very basic:
reading data from multiple analog input ports and displaying the values on the PC (transfer via serial connection).
the problem that appears:
everything works fine, when putting NO delay between the analogRead statements, but when i have a delay in between, random values (mostly the same on 2 or more ports) are displayed.
i'm aware of the fact that the capacitor of the sample-hold needs to charge when using high-impedance inputs, but first of all, i am not using more than max 10k input impedance (potentiometers) on the inputs and secondly, two readings on the same input à la
analogRead(A0);
delay(10);
val0 = analogRead(A0);
analogRead(A1);
delay(10);
val1 = analogRead(A1);
will not work either.
to make things a little clearer:
i used the hardware setup as depicted in the attached png. (i haven't used fritzing before and didnt want to spend too much time on it now, so please be gentle ^^). the voltage source is actually not a battery, but a power supply, delivering constant 3.3 V. the resistors of the voltage divider are R1 = 8.05k and R2 = 1.56k, so the voltage on pin0 should be 3.3*1.067/(8.056+1.067) = 0.385 V.
now, this code works just fine:
//declare ports
const int analogPin0 = A0;
const int analogPin1 = A1;
const int analogPin2 = A2;
int pin0Val = 0, pin1Val = 0, pin2Val = 0;
int pin0mV, pin1mV, pin2mV = 0;
void setup() {
Serial.begin(19200);
}
void loop() {
pin0Val = analogRead(analogPin0);
pin1Val = analogRead(analogPin1);
pin2Val = analogRead(analogPin2);
pin0mV = pin0Val*3300/1023;
pin1mV = pin1Val*3300/1023;
pin2mV = pin2Val*3300/1023;
Serial.print(millis());
Serial.print(',');
Serial.print(pin0mV);
Serial.print(',');
Serial.print(pin1mV);
Serial.print(',');
Serial.println(pin2mV);
delay(500);
}
whereas this doesn't:
//declare ports
const int analogPin0 = A0;
const int analogPin1 = A1;
const int analogPin2 = A2;
int pin0Val = 0, pin1Val = 0, pin2Val = 0;
int pin0mV, pin1mV, pin2mV = 0;
void setup() {
Serial.begin(19200);
}
void loop() {
pin0Val = analogRead(analogPin0);
delay(10);
pin0mV = pin0Val*3300/1023;
pin1Val = analogRead(analogPin1);
delay(10);
pin1mV = pin1Val*3300/1023;
pin2Val = analogRead(analogPin2);
delay(10);
pin2mV = pin2Val*3300/1023;
Serial.print(millis());
Serial.print(',');
Serial.print(pin0mV);
Serial.print(',');
Serial.print(pin1mV);
Serial.print(',');
Serial.println(pin2mV);
delay(500);
}
this second code delivers the millis correctly and three equal values for the printouts of the ports.
interestingly, both codes work with the arduino UNO however... ...and as mentioned above: if i change the code to read the same port twice, with a short delay, it doesn't work either.
by the way: i'm using Arduino 1.5.5.-r2.
thx in advance for your help! 
