Blink LED when a button is pressed - GPIO/LED/Button Example

To create a bash script for an i.MX8MP that makes an LED blink when a button is pressed, you'll need to use the GPIO (General Purpose Input/Output) pins on the i.MX8MP. Here's a simple example using a button connected to GPIO5_IO08 and an LED connected to GPIO5_IO09:

• GPIO5_IO08 (GPIO number 136 in Linux)
• GPIO5_IO09 (GPIO number 137 in Linux)

Here can find more information about how to control on the i.MX8MP GPIOs

1. Connect a button to GPIO5_IO08 and ground (GND), and connect an LED to GPIO5_IO09 and a current-limiting resistor, then to ground (GND). - for simple test you can use the GPIOs of the HummingBoard-Pulse/Ripple imx8mp; MikroBus (J10[1] and J10[2])
2. Create a bash script using a text editor. For example, use the following command to create a script named blink_button.sh

#!/bin/bash
# Define GPIO pin numbers
BUTTON_PIN=136
LED_PIN=137
# Set up GPIO pins
echo "$BUTTON_PIN" > /sys/class/gpio/export
echo "$LED_PIN" > /sys/class/gpio/export
echo "in" > "/sys/class/gpio/gpio$BUTTON_PIN/direction"
echo "out" > "/sys/class/gpio/gpio$LED_PIN/direction"
# Function to turn on the LED
turn_on_led() {
   echo 1 > "/sys/class/gpio/gpio$LED_PIN/value"
}
# Function to turn off the LED
turn_off_led() {
   echo 0 > "/sys/class/gpio/gpio$LED_PIN/value"
}
# Main loop
while true; do
   # Check the state of the button
   button_state=$(cat "/sys/class/gpio/gpio$BUTTON_PIN/value")
   # If the button is pressed (value is 0), turn on the LED
   if [ "$button_state" -eq 0 ]; then
       turn_on_led
   else
       turn_off_led
   fi
   # Sleep for a short duration to avoid high CPU usage
   sleep 0.1
done

Your LED should blink when the button is pressed.

Note that this script continuously checks the state of the button in a loop. You can stop the script by pressing Ctrl + C.