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Lighting Up the First LED

Introduction​

Most people start learning embedded MCU programming by lighting up an LED. Learning MicroPython on the WalnutPi PicoW is no exception. Lighting up your first LED helps you understand the development environment and program architecture, building a strong foundation for future learning and larger projects while boosting your confidence.

Objective​

Learn to light up an LED (blue LED).

Experiment Explanation​

The WalnutPi PicoW has an LED connected to a GPIO that can be controlled.

led

From the schematic, we can see that the blue LED corresponds to chip IO pin 46. From the circuit, when IO46 is high, the blue LED lights up. led

Controlling the LED uses the Pin object from the machine module. Usage instructions are as follows:

Pin Object​

Pin is a pin object.

Constructor​

from machine import Pin

LED = Pin(id, mode, pull)

Pin is located under the machine module and can be used by directly importing it:

  • id : Chip pin number, e.g., 1, 2, 46.
  • mode : Input/output mode.
    • Pin.IN : Input mode;
    • Pin.OUT : Output mode;
  • pull: Pull-up/pull-down resistor configuration.
    • None : No pull-up/pull-down resistor;
    • Pin.PULL_UP : Pull-up resistor enabled;
    • Pin.PULL_DOWN : Pull-down resistor enabled.

Usage​

LED.value([X])

Configure pin level:

  • Output mode : Output level value.
    • 0 : Output low level;
    • 1 : Output high level.
  • Input mode : No parameters needed, gets the current pin input level.

LED.on()

Outputs high level "1", 3.3V.


LED.off()

Outputs low level "0", 0V.


For more usage, refer to the official documentation:
https://docs.micropython.org/en/latest/library/machine.Pin.html#machine-pin

The table above provides a detailed explanation of the Pin object in MicroPython's machine module. machine is the main module, and Pin is one of its submodules. There are two ways to reference related modules in Python programming:

  • Method 1: import machine, then operate via machine.Pin;

  • Method 2: from machine import Pin, which directly imports the Pin module from machine, then operates by constructing a led object. Method 2 is clearly more intuitive and convenient, and this experiment uses Method 2 for programming.

The code writing flow is as follows:

Reference Code​

'''
Experiment Name: Light up the blue LED
Version: v1.0
'''

from machine import Pin #Import Pin module

LED=Pin(46,Pin.OUT) #Build LED object, GPIO46, output
LED.value(1) #Light up LED, or use led.on()

Experimental Results​

Run the above code in Thonny IDE:

led1

You can see the blue LED lights up.

led1

From this first experiment, we can see that the key to MicroPython development is learning the constructor and its usage methods to operate related objects. With powerful module functions, the experiment achieved lighting up an LED with just two simple lines of code.