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2.7 Toggle Left and Right
In this lesson, we’ll learn how to use a slide switch with the Raspberry Pi Pico 2 to detect its position (left or right) and perform actions based on that. A slide switch is a simple mechanical device that connects the common (middle) pin to one of the two outer pins depending on its position.
What You’ll Need
In this project, we need the following components.
It’s definitely convenient to buy a whole kit, here’s the link:
Name |
ITEMS IN THIS KIT |
LINK |
|---|---|---|
Newton Lab Kit |
450+ |
You can also buy them separately from the links below.
SN |
COMPONENT |
QUANTITY |
LINK |
|---|---|---|---|
1 |
1 |
||
2 |
Micro USB Cable |
1 |
|
3 |
1 |
||
4 |
Several |
||
5 |
1(10KΩ) |
||
6 |
1(104) |
||
7 |
1 |
Understanding the Slide Switch
A slide switch has three pins:
Pin 1: Connected when the switch is toggled to one side (e.g., left)
Pin 2: Common pin (middle pin)
Pin 3: Connected when the switch is toggled to the other side (e.g., right)
By reading the voltage on the common pin, we can determine the position of the switch.
Circuit Diagram
GP14 will get a different level, when you toggle the slide switch to the right or left.
The purpose of the 10K resistor is to keep the GP14 low during toggling (not toggling to the far left and not toggling to the far right).
When you toggle the switch, the mechanical contacts can cause rapid, noisy signals known as “bounce.” The capacitor connected between GP14 and GND helps to filter out these rapid fluctuations, providing a cleaner signal.
Switch Toggled to the Right:
Pin 2 (GP14) is connected to 3.3V through Pin 1.
The GPIO pin reads HIGH (1).
Switch Toggled to the Left:
Pin 2 (GP14) is connected to GND through Pin 3.
The GPIO pin reads LOW (0).
Switch in the Middle Position:
Pin 2 (GP14) is not connected to either 3.3V or GND.
The pull-down resistor keeps the GPIO pin at LOW (0).
The capacitor helps to reduce switch bounce (noise due to mechanical movement).
Wiring
Writing the Code
We’ll write a MicroPython program that detects the position of the slide switch and prints a message accordingly.
Note
Open the
2.7_slide_switch.pyfromnewton-lab-kit/micropythonor copy the code into Thonny, then click “Run” or press F5.Ensure the correct interpreter is selected: MicroPython (Raspberry Pi Pico).COMxx.
import machine
import utime
# Initialize GP14 as an input
slide_switch = machine.Pin(14, machine.Pin.IN)
while True:
switch_state = slide_switch.value()
if switch_state == 1:
print("Switch is toggled to the LEFT!")
else:
print("Switch is toggled to the RIGHT!")
utime.sleep(0.5)
When the code is running, you will observe the following phenomenon:
Toggle to the Right: You should see “Switch is toggled to the RIGHT!” in the console.
Toggle to the Left: You should see “Switch is toggled to the LEFT!” in the console.
Understanding the Code
Import Modules:
import machine: Access hardware functions.import utime: Use time-related functions.
Initialize the Slide Switch Pin:
slide_switch = machine.Pin(14, machine.Pin.IN): Sets up GP14 as an input pin.
Main Loop:
while True: Creates an infinite loop to continuously check the switch state.switch_state = slide_switch.value(): Reads the current state of the switch.if switch_state == 1: Checks if the GPIO pin is HIGH (switch toggled to the left).print("Switch is toggled to the RIGHT!"): Prints a message.else: If the GPIO pin is LOW (switch toggled to the right or in the middle).print("Switch is toggled to the LEFT!"): Prints a message.utime.sleep(0.5): Adds a short delay to debounce the switch and avoid flooding the console.
Alternative: Using an internal pull-down resistor
The Raspberry Pi Pico 2 allows us to enable internal pull-down resistors, eliminating the need for an external resistor.
Modify the Circuit:
Remove the external 10 kΩ resistor and 0.1 µF capacitor.
Modified Code:
import machine import utime # Initialize GP14 as an input with internal pull-down resistor slide_switch = machine.Pin(14, machine.Pin.IN, machine.Pin.PULL_DOWN) while True: switch_state = slide_switch.value() if switch_state == 1: print("Switch is toggled to the LEFT!") else: print("Switch is toggled to the RIGHT!") utime.sleep(0.5)
Practical Applications
Mode Selection: Use the switch to toggle between different modes in your program.
Power Control: Control power to certain parts of your circuit.
User Input: Provide simple user controls for your projects.
Experimenting Further
Add an LED Indicator:
Connect an LED to another GPIO pin (e.g., GP15) with a suitable resistor.Modify the code to turn the LED on or off based on the switch position.
import machine import utime slide_switch = machine.Pin(14, machine.Pin.IN, machine.Pin.PULL_DOWN) led = machine.Pin(15, machine.Pin.OUT) while True: if slide_switch.value() == 1: led.value(1) # Turn on the LED else: led.value(0) # Turn off the LED utime.sleep(0.1)
Detect Middle Position:
To detect when the switch is in the middle (neither left nor right), you’ll need to modify the wiring and code to read all three states.
Conclusion
Using a slide switch with the Raspberry Pi Pico 2 allows you to add physical input controls to your projects. By understanding how to read the switch’s state and handle potential issues like switch bounce, you can create more interactive and user-friendly applications.