1. You could refer Cypress standard example project to implement Interrupt. This Application can help you understand Interrupt in M0+ core to help you out.
2. If you just need a example code for both edge, I have a example for your referring.
a. Add a GPIO and ISR type in your project.
b. In your project, You shall add below code into your project.
(1) Interrupt handle function
if (GPIO_0_Read() == false)
.... //<< Add failing edge function here
if (GPIO_0_Read() == true)
....//<< Add rising edge function here
* Interrupt Service Routine to handle the interrupts triggered
* on the falling edge of the GPIO_0 input signal
GPIO_0_ClearInterrupt(); // Clears any active interrupts attached with the GPIO_0 component
(2) Initial interrupt
GPIO_0_ClearInterrupt(); // Clears any active interrupts attached with the USER_BUTTON component
/* Sets up the interrupt to function and sets address as the ISR vector for the interrupt */