Digital and Analog Pins

In this chapter we will learn about managing digital and analog pins.

All the compatible boards have a series of pins, most of these pins work as a general-purpose input/output (GPIO) pin. There are Digital Pins and Analog Pins depending on the signal. We will learn how to use the inputs and outputs.

There are essentially two types of pins, analog and digital pins. Digital pins can be set to either HIGH (usually 5V or 3.3V) or LOW (0V). You can use that to e.g. read a button state or toggle an LED.

Important: unfortunately, the MicroPython implementation does not match the regular pinout of your board. This means, that if you want to use for example, digital pin (5), it might be digital pin (27) on one board, or digital pin (14) on another. Please visit the Board API article to see what the pin map for your board is.

Digital Pins

Digital signals have two distinct values: HIGH (1) or LOW (0). You use digital signals in situations where the input or output will have one of those two values. For example, you can use a digital signal to turn an LED on or off.

Digital Write

In this section we will introduce the

machine

myLED

In MicroPython we can declare a

Pin

25

Pin.OUT

Finally, to turn the pin to a high or low state, we set the

value

1

0

Copy
1from machine import Pin #import pin function 
2
3myLED = Pin(25, Pin.OUT) #declare pin 25 as an output
4
5myLED.value(1) #set pin to a high state (1) / ON
6myLED.value(0) #set pin to a low state (0) / OFF

To create the classic "blink" example, we can also import the

time

while

The following example blinks the onboard LED every second.

Copy
1from machine import Pin
2import time
3
4myLED = Pin(25, Pin.OUT) #Nano RP2040 Connect
5#myLED = Pin(10, Pin.OUT) #Nano 33 BLE / Nano 33 BLE Sense
6#myLED = Pin(2, Pin.OUT) #Portenta H7
7
8
9while True:
10    myLED.value(0)
11    time.sleep(1)  
12    myLED.value(1)
13    time.sleep(1)

Digital Read (Pull Up)

In this example we read a digital value from a digital pin, using the

PULL_UP

Pin.IN

Then, we use

p2.value()

Copy
1from machine import Pin
2import utime
3
4p2 = Pin(25, Pin.IN, Pin.PULL_UP)
5
6while True:
7    print(p2.value())
8    utime.sleep(1)

Digital Read (Pull Down)

In this example we read a digital value from a digital pin, using the

PULL_DOWN

Pin.IN

Then, we use

p2.value()

Copy
1from machine import Pin
2import utime
3
4p2 = Pin(25, Pin.IN, Pin.PULL_DOWN)
5
6while True:
7    print(p2.value())
8    utime.sleep(1)

Analog Pins

An example of the analog pin is the ADC class, which supplies an interface to analog-to-digital converters, and figures a single endpoint that can sample a continuous voltage and convert it to a discretized value.

There are four methods to use inside the ADC class:

ADC.init

ADC.block()

ADC.read_16()

ADC.read_uv()

Analog Read

To read an analog pin, we can use the

ADC.read_u16

ADC

Pin

machine

Copy
1import machine
2import time
3
4# Make sure to follow the GPIO map for the board you are using.
5# Pin 29 in this case is the "A3" pin on the Nano 33 BLE / BLE Sense
6adc_pin = machine.Pin(29) 
7adc = machine.ADC(adc_pin)
8
9while True:
10    reading = adc.read_u16()     
11    print("ADC: ",reading)
12    time.sleep_ms(500)

If you are using an Arduino Nano RP2040 Connect, you can also do the following:

adc = ADC("A4")

PWM (Pulse Width Modulation)

PWM is used to produce analog results with digital means, by switching ON/OFF a signal rapidly.

As a result, you can simulate a specific voltage written to a pin. In the example below, we write

30000

For this, we need to import

PWM

Pin

machine

Copy
1from machine import Pin, PWM, ADC
2
3pwm = PWM(Pin(15))
4duty = 30000 #between 0-65000
5
6pwm.freq(1000)
7
8while True:
9    pwm.duty_u16(duty)