Hi here is my solution:
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
}
unsigned int analogReadReference(void) {
/* Elimine toutes charges résiduelles */
ADCSRB &= ~(1 << MUX5);
ADMUX = 0x5F;
delayMicroseconds(5);
/* Active le convertisseur analogique -> numérique */
ADCSRA |= (1 << ADEN);
/* Lance une conversion analogique -> numérique */
ADCSRA |= (1 << ADSC);
/* Attend la fin de la conversion */
while(ADCSRA & (1 << ADSC));
}
void loop() {
for (int k=0;k<4;k++){
for (int j=0;j<4;j++){
for (int i=0; i < 4; i++) {
(void)analogRead(A15);
int sv0 = analogRead(A15);
unsigned int raw_ref = analogReadReference();
(void)analogRead(A7);
int sv1 = analogRead(A7);
raw_ref = analogReadReference();
(void)analogRead(A0);
int sv2 = analogRead(A0);
raw_ref = analogReadReference();
Serial.print(sv2);Serial.print(" av1=");Serial.print(sv1);Serial.print(" av2=");Serial.println(sv);
my solution is based of the configuration of the ADC of the ATmega 2560 and i got this informations from the datasheet of CPU ATmega 2560, so we can eliminate the residual charge, activate the ADC and beginning new conversion.
yes Grumpy the impedance of sensors is very high, it's responsible of the main problem.
thanks wawa for the solution and i will try it as soon.
thank you very much for your time and your help