flipper-zero-tutorials/gpio/gpio_interrupt_demo

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

  • See basic demo for explanation.

• basic_demo.png

  • See basic demo for explanation.

• 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.