Case 02: Button
4. Case 02: Button#
The Momentary push-button switches are electronic components that are used in daily life mainly to connect and disconnect circuits. In the previous lesson we have learnt how to use Pico:ed to control 2 LEDs flashing alternately. Here we will use a momentary push button switch to control the flashing of the 2 LEDs. When we press the button, the 2 LEDs will blink alternately; release the button, the LEDs will stop blinking.
4.2. Components List#
1 × Pico:ed
1 × USB Cable
1 × Breadboard Adapter
1 × 83×55mm Breadboard
2 × LEDs
2 × 100Ω Resistors
1 × Momentary Push Button
N* Dupont Cables
4.3. Main Components#
Momentary Push Button#
This is a common component used to control electronic devices. It is mostly used to connect or disconnect control circuits to enable the control of motors or other electronic devices. The momentary push-button switch is usually kept open. When it is pressed, the circuit is switched on; when it is popped up, it jumps back to the unconnected state.
The momentary push button switch has 4 pins which can be divided into 2 groups, pin 1 shorted to pin 2 and pin 3 shorted to pin 4 .
Connect your components according to the following pictures:
Connect the shorter pin of the led light to GND
Connect the longer pin of the led to the P0 port and the P1 port through the resistors.
Connect the momentary push button switch to port P2
The picture shows the project after getting the compoents connected:
Program Preparation: Prpgramming environment
# Import the modules that we need: import board import digitalio import time # Set the connencted pins and their directions of the LEDs led_0 = digitalio.DigitalInOut(board.P0_A0) led_1 = digitalio.DigitalInOut(board.P1_A1) led_0.direction = digitalio.Direction.OUTPUT led_1.direction = digitalio.Direction.OUTPUT # Set the connected pins of the button and pull it up. button = digitalio.DigitalInOut(board.P2_A2) button.direction = digitalio.Direction.INPUT button.pull = digitalio.Pull.UP # Set to change the status of the LEDs with the status of the button. while True: if button.value == False: led_0.value = True led_1.value = False time.sleep(1) led_0.value = False led_1.value = True time.sleep(1)
Details of the Code:#
Import the modules that we need.
boardis the common container, and you can connect the pins you’d like to use through it. The
digitaliomodule contains classes to provide access to basic digital IO.
timeis the module contains the fuction of time setting.
import board import digitalio import time
Set the connected pins and the directions of the LED.
led_0 = digitalio.DigitalInOut(board.P0_A0) led_1 = digitalio.DigitalInOut(board.P1_A1) led_0.direction = digitalio.Direction.OUTPUT led_1.direction = digitalio.Direction.OUTPUT
Set the connected pins of the button and pull it up.
button = digitalio.DigitalInOut(board.P2_A2) button.direction = digitalio.Direction.INPUT button.pull = digitalio.Pull.UP
If the pins you are using are not P0_A0, P1_A1 and P2_A2, the other pin numbers can be viewed by entering the following code in the shell window below the Thonny editor.
>>> import board >>> help(board) object <module 'board'> is of type module __name__ -- board board_id -- elecfreaks_picoed BUZZER_GP0 -- board.BUZZER_GP0 I2C0_SDA -- board.BUZZER_GP0 I2C0_SCL -- board.I2C0_SCL BUZZER -- board.BUZZER BUZZER_GP3 -- board.BUZZER P4 -- board.P4 P5 -- board.P5 P6 -- board.P6 P7 -- board.P7 P8 -- board.P8 P9 -- board.P9 P10 -- board.P10 P11 -- board.P11 P12 -- board.P12 P13 -- board.P13 P14 -- board.P14 P15 -- board.P15 P16 -- board.P16 SDA -- board.SDA P20 -- board.SDA SCL -- board.SCL P19 -- board.SCL BUTTON_A -- board.BUTTON_A BUTTON_B -- board.BUTTON_B SMPS_MODE -- board.SMPS_MODE VBUS_SENSE -- board.VBUS_SENSE LED -- board.LED P0_A0 -- board.P0_A0 P0 -- board.P0_A0 A0 -- board.P0_A0 P1_A1 -- board.P1_A1 P1 -- board.P1_A1 A1 -- board.P1_A1 P2_A2 -- board.P2_A2 P2 -- board.P2_A2 A2 -- board.P2_A2 P3_A3 -- board.P3_A3 P3 -- board.P3_A3 A3 -- board.P3_A3
Set to control the LED with the button.
while True: if button.value == False: led_0.value = True led_1.value = False time.sleep(1) led_0.value = False led_1.value = True time.sleep(1)
Press the button and the two LEDs flash alternately; release the button and they will trun off, if this is not the case, please check your applications.
How to program to light on in red while pressing the button and light on in green after releasing it?