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Embedded device utilities in C

Utility libraries for embedded devices written in C. Easily portable to any device.

Concept

Each utility (buttons, lcd, ...) is split on two parts: implementation part (portable logic) and user part (MCU or user specific handlers). For example (buttons):

  • buttons.h, buttons.c: logic that determines if button events should be generated (call user callbacks). User does not need to modify these files as there is no MCU-specific code (as long as library behaviour must not be changed).
  • buttons_user.h, buttons_user.c: user implementation of low level GPIO read (MCU specific) and button events callback functions.

Buttons

buttons.h, buttons.c, buttons_user.h, buttons_user.c
This is a generic button handling library that supports:

  • debouncing and event generation
  • select key press mode: single press, repetitive presses, single/long press
  • callback functions based on button event&mode
  • generic code, that is easily portable on any device
  • simple API that does not require interrupts or special timers (rely on systick/generic millisecond timer):
    • user need to add only low layer function call to get GPIO state
    • register new button with btn_register()
    • handle buttons with btn_handle()
    • handle events in functions: btn_on_press() and btn_on_longpress() in user-specific files

Ring buffer

ring_buffer.h, ring_buffer.c
This is a FIFO (ring) buffer to store data, with simple API that allow user to:

  • put number of bytes into the buffer
  • get number of bytes from the buffer
  • check buffer size, state and free space
  • handle error checking by returning status

UART print

uart_print.h, uart_print.c, uart_print_user.h, uart_print_user.c
This is an Arduino-inspired library for embedded devices, that allows user to send printable data over UART with simple API.

  • numbers (signed/unsigned integers, floats) with selective base (DEC, BIN, HEX, OCT)
  • strings
  • new-line characters
  • User only need to implement UART 'send byte(s)' low layer call, while formatting is done by this library.

LCD

lcd.h, lcd.c, lcd_user.h, lcd_user.c
This is a generic LCD HD44780-based library that supports:

  • printing strings
  • printing numbers (integers, floats)
  • printing strings in a specific window (optional scrolling)
  • creating and printing custom characters
  • controlling of LCD settings like: display on/off, cursor blinking on/off, scrolling, clearing

Rotary encoder

rot_enc.h, rot_enc.c, rot_enc_user.h, rot_enc_user.c
This is a generic, single-interrupt based library to handle basic three-pin (2 GPIO + common pin) rotary encoder. Library supports:

  • reading difference from the last read (last get function call)
  • reading absolute value from the last reset action
  • setting count direction
  • reset count value NOTE: User must manually implement interrupt routine (and set irq priority) on rising & falling edge on one rotary encoder pin, and call rot_enc_update() function. This ensure library to register all rotary encoder interactions, and properly debounce any glitches so that the count is a valid number.

Examples (STM32)

See examples in SunAlarm and STM32 USB Shortcutter (programable keys) project.