Quick Reference
Configuring an Analog Output Pin
Arduino
Most boards don't have true analog output.
CircuitPython
import board
import analogio
dac = analogio.AnalogOut(board.A1)
Using an Analog Output Pin
Arduino
Most boards don't have true analog output.
CircuitPython
dac.value = 32767
Configuring a PWM Output Pin
Arduino
Nothing required
CircuitPython
import boardimport pwmio
led = pwmio.PWMOut(board.A1)
Using a PWM Output Pin
Arduino
analogWrite(9, 128);
CircuitPython
led.duty_cycle = 32767
Discussion
Arduino
Writing to an analog pin is straight forward. This is generally not technically a true analog value, but rather a PWM signal. I.e. the value you are writing sets the duty-cycle of the PWM signal. The range is 0-255, inclusive. The analogWrite is used for this and, like digitalWrite, takes the pin and value.
The Arduino DUE has 2 actual analog to Digital converters that output an actual analog voltage rather than a PWM signal.
analogWrite(pin, val);
Putting it together, we can read from an analog pin and write to another. The difference is value ranges needs to be accommodated, and that's what the division by 4 accomplishes.
int ledPin = 9; // LED connected to digital pin 9
int analogPin = 3; // potentiometer connected to analog pin 3
int val = 0; // variable to store the read value
void setup()
{
pinMode(ledPin, OUTPUT); // sets the pin as output
}
void loop()
{
val = analogRead(analogPin); // read the input pin
analogWrite(ledPin, val / 4); // analogRead values go from 0 to 1023, analogWrite values from 0 to 255
}
CircuitPython
There are two types of analog output available on CircuitPython hardware: true analog and PWM (as on Arduino).
For true analog output, the value parameter of the AnalogOut object is set to a value between 0 and 65535, the same range as seen in AnalogInput's value range: 0 sets the output to 0v and 65535 sets it to the reference voltage.
dac.value = 32767
A related output capability is PWM (Pulse Width Modulation). It's done in a completely different way. Instead of using the analogio module, you'll need to use pulseioand create a PWMOut object using the Pin on which you want to generate the signal.
>>> import board >>> import pulseio >>> led = pulseio.PWMOut(board.A1)
Once you have a PWMOut object, you can set it's duty cycle (the percent of time the output is high) as a 16 bit interger (0-65535). For example:
# set the output to 100% (always high) >>> led.duty_cycle = 65535 # set the output to 0% (always low) >>> led.duty_cycle = 0 # set the output to 50% (high half the time) >>> led.duty_cycle = 32767
