smooth输入（10个值平均值，新值与前9个值）
int readings[numReadings];
void loop() {
total= total - readings[readIndex];
readings[readIndex] = analogRead(inputPin);
total= total + readings[readIndex];
readIndex = readIndex + 1;
if (readIndex >= numReadings)
readIndex = 0;
average = total / numReadings;}
