Button and LED module

• The XRP controller (Raspberry Pi Pico and other electronics), software (Micropython and XRPlib), and mechanical platform are designed to allow additional components to be added.

• In this exercise, we'll add a button and LED module.

• The parts needed include:

  • Grove - LED Button

  • Qwiic Cable - Grove Adapter (100mm)

  • Button_LED_board_connector (3D-print) - [https://www.thingiverse.com/thing:6669721]

  • (3) M2x12mm bolts and nuts

Button Programming

• The button on the Button LED module is connected to the IO4 pin of the Pico.
  (This pin is "QWIIC 0" and is intended to be used as a 2nd I2C bus, but it isn't connected to other components on the XRP Controller Board.)

• This is not the same pin as the user button on the Pico board

• XRP Code Editor Blockly code cannot control pin IO4 but we can use MicroPython to read the button status.

• In the XRP Code Editor, click File ... New and select "MICRO PYTHON"

• Copy this Python program and paste it into the new program window:

from XRPLib.board import Board

import time

from machine import Pin

from machine import Timer

from XRPLib.defaults import imu 

board = Board.get_default_board()

ext_led = Pin(5, Pin.OUT)

ext_button_pin = Pin(4, Pin.IN, Pin.PULL_UP) #note that IO4 may be used for I2C by XRPLib

print("")

print("Press external to turn the LED on; Press user button to turn it off.")

while True:

    if board.is_button_pressed():

        ext_led.off()

        print("User Button!")

        time.sleep(0.2)          # Debounce delay to prevent multiple triggers per press

        print("XRP heading: ", imu.get_heading())

    if ext_button_pin.value() == 0:  # Button is pressed (connected to GND)

        print("External Button!")

        ext_led.on()

        time.sleep(0.2)          # Debounce delay to prevent multiple triggers per press

    time.sleep(0.05)             # Small delay to reduce CPU usage

• Click "RUN"

• Is the LED on the Button LED module turning on when you press the external button, and off when you press the user button?

• If not, check the Grove / qwiic cable connections

• Also, when the user button is pressed, the current heading (magnetic orientation) of the XRP is printed on the console.
  (The IMU uses the  QWIIC 1 bus, so  using the QWIIC 0  pin for the external button isn't affecting the  use of the IMU.)
  See get_heading() XRP API Reference

A better way to blink

• Here is a better way to blink an LED in Micropython using the timer and interrupt functionality:
  https://github.com/raspberrypi/pico-micropython-examples/blob/master/blink/blink.py
  Added while True ... board.wait_for_button to show that the LED continues to blink while waiting.
  (There are other Pico MicroPython example in this Gihub for you to explore.)

from XRPLib.board import Board

import time

from machine import Pin

from machine import Timer

board = Board.get_default_board()

led = Pin(5, Pin.OUT)

tim = Timer()

def tick(timer):

    global led

    led.toggle()

tim.init(freq=2.5, mode=Timer.PERIODIC, callback=tick)

while True:

  board.wait_for_button()

  print("Button!")