analogRead(pin)
Reads the value from a specified analog pin with a 10-bit resolution. This function only works on the analog in pins (0-5). The resulting integer values range from 0 to 1023.
value = analogRead(pin); // sets 'value' equal to 'pin'
Note: Analog pins unlike digital ones, do not need to be first declared as INPUT nor OUTPUT.
analogWrite(pin, value)
Writes a pseudo-analog value using hardware enabled pulse width modulation (PWM) to an output pin marked PWM. On newer Arduinos with the ATmega168 chip, this function works on pins 3, 5, 6, 9, 10, and 11. Older Arduinos with an ATmega8 only support pins 9, 10, and 11. The value can be specified as a variable or constant with a value from 0-255.
analogWrite(pin, value); // writes 'value' to analog 'pin'
A value of 0 generates a steady 0 volts output at the specified pin; a value of 255 generates a steady 5 volts output at the specified pin. For values in between 0 and 255, the pin rapidly alternates between 0 and 5 volts - the higher the value, the more often the pin is HIGH (5 volts). For example, a value of 64 will be 0 volts three-quarters of the time, and 5 volts one quarter of the time; a value of 128 will be at 0 half the time and 255 half the time; and a value of 192 will be 0 volts one quarter of the time and 5 volts three-quarters of the time.
Because this is a hardware function, the pin will generate a steady wave after a call to analogWrite in the background until the next call to analogWrite (or a call to digitalRead or digitalWrite on the same pin).
Note: Analog pins unlike digital ones, do not need to be first declared as INPUT nor OUTPUT.
The following example reads an analog value from an analog input pin, converts the value by dividing by 4, and outputs a PWM signal on a PWM pin:
int led = 10; // LED with 220 resistor on pin 10
int pin = 0; // potentiometer on analog pin 0
int value; // value for reading
void setup(){} // no setup needed
void loop()
{
value = analogRead(pin); // sets 'value' equal to 'pin'
value /= 4; // converts 0-1023 to 0-255
analogWrite(led, value); // outputs PWM signal to led
}
