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BASIC DEMO

Introduction

This is a basic demo of using GPIO interrupts.

Installation Directions

This project is intended to be overlayed on top of an existing firmware repo.

  • Clone, Build & Deploy an existing flipper zero firmware repo. See this tutorial for updating firmware.
  • Copy the "gpio_interrupt_demo" folder to the \applications\plugins\gpio_interrupt_demo folder in your firmware.
  • Build & deploy the firmware. See this tutorial for updating firmware.
  • NOTE: You can also extract the gpio_interrupt_demo.FAP from resources.tar file and use qFlipper to copy the file to the SD Card/apps/Misc folder.

Connecting the hardware

GPIO pin C3 is our interrupt pin (with internal pull-up resistor). I connect pin to a 220 ohm resistor and then the other side of the resistor to one side of a momentary switch. Other side of the switch connects to our GND pin.

GPIO A7, A6 and A4 connect to 220ohm resistors then the + or - pins of LED... LED1: +A7 -A6 LED2: +A6 -A7 LED3: +A7 -A4 LED4: +A4 -A7 LED5: +A6 -A4 LED6: +A4 -A6

Running the updated firmware

These directions assume you are starting at the flipper desktop. If not, please press the back button until you are at the desktop.

  • Press the OK button on the flipper to pull up the main menu.

  • Choose "Applications" from the menu.

  • Choose "GPIO" from the sub-menu.

  • Choose "GPIO Interrupt Demo"

  • Message "GND pin C3 to stop." should display

  • LEDs should blink in order.

  • press switch (or connect wire/resistor between C3 and GND)

  • LEDs should stop and display should say "Stopped on LED 4." (or whatever LED was lit.)

  • Press DOWN button on Flipper Zero to start over.

  • Press the BACK button to exit.

How it works

  • application.fam

  • basic_demo.png

  • basic_demo_app.c

    • GPIO specific code:
      • furi_hal_gpio_init(&gpio_ext_pc3, GpioModeInterruptFall, GpioPullUp, GpioSpeedVeryHigh);
        • gpio_ext_pc3 is the GPIO pin we are using for interrupt input.
        • GpioModeInterruptFall - means trigger callback on falling edge (VCC->GND)
        • GpioModeInterruptRise - means trigger callback on rising edge (GND->VCC)
        • GpioModeInterruptRiseFall - means trigger callback on either edge
        • GpioPullUp - Means enable internal pull-up resistor between VCC and pin.
        • GpioPullDown - Means enable internal pull-down resistor between GND and pin.
        • GpioPullNo - Means do not enable internal pull-up/pull-down resistor.
        • GpioSpeedVeryHigh - priority of input?
      • furi_hal_gpio_add_int_callback(&gpio_ext_pc3, demo_gpio_fall_callback, NULL);
        • gpio_ext_pc3 is the GPIO pin we are using for interrupt input.
        • second parameter is callback with signature: "void fnName(void* ctx)"
        • third parameter is object to pass into callback for context (or NULL if no object).
        • once furi_hal_gpio_add_int_callback is invoked, the callback is enabled.
      • demo_gpio_fall_callback(void* ctx)
        • this method gets invoked by our callback (because of previous add_int_callback) wheneven pin C3 gets pulled to GND.
        • interrupt callbacks should try to do mininal amount of processing.
      • furi_hal_gpio_remove_int_callback(&gpio_ext_pc3);
        • removes the callback, so method is no longer invoked on pin transistion.