RaspberryLCD

A small library to communicate with an LCD screen, intended for use with a RaspberryPi and the WiringPi library.

This library handles the entire communication on the hardware level and supplies the user with high-level bindings for the most common uses. This library also encoded the non-ascii characters supported by LCD screens (Japanese Katakana and mathematical symbols), in order to make using the screen as easy as possible.

Example

#include "raspberrylcd.h"

int main(int argc, char** argv)
{
    LCDScreen screen;
    configurePins(&screen, 7, 9, 8, 0, 0, 0, 0, 21, 22, 23, 24);

    initScreen(&screen, HALF_BYTE_INTERFACE, TWO_LINES, FONT_5x7, CURSOR_ON | CURSOR_BLINK, LEFT_TO_RIGHT);
    sendText(&screen, "スウェーデン");
    setCursor(&screen, 0, 1);
    sendText(&screen, "オーストラリア");
    resetPins(&screen);

    return 0;
}

---

This snippet produces the following output on my LCD screen:

Functions

All functions take a pointer to LCDScreen as their first parameter

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LCDScreen* configurePins(LCDScreen* screen, uint8_t RS, uint8_t RW, uint8_t E, uint8_t D0,uint8_t D1, uint8_t D2, uint8_t D3, uint8_t D4, uint8_t D5, uint8_t D6, uint8_t D7);

This function tells the LCDScreen what pins to use to controll the LCD screen. Make sure to check with WiringPi which GPIO pin has which pin number. If you choose to operate your screen in 4-bit mode you can set D0-D4 to 0.

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void initScreen(LCDScreen* screen, uint8_t interface_bits, uint8_t num_lines, uint8_t fontType, uint8_t cursor, uint8_t writeDirection);

This function performs the initialization steps on the LCD screen. Make sure to choose your configuration wisely, as it cannot be changed without re-initializing the screen.

• interface_bits controls the amount of bits used to communicate with the screen.

  • 4-bit mode: HALF_BYTE_INTERFACE
  • 8-bit mode: FULL_BYTE_INTERFACE

• num_lines can either be ONE_LINE or TWO_LINES. If you choose to use the 5x10 font you must set this to ONE_LINE.

• font_type sets the font type. Can either be FONT_5x10 or FONT_5x7.

• cursor configures the cursor behaviour. You can bitwise OR the following

  • CURSOR_OFF / CURSOR_ON
  • CURSOR_STATIC / CURSOR_BLINK

• writeDirection sets the direction of writing for the display. Either LEFT_TO_RIGHT or RIGHT_TO_LEFT.

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void resetPins(LCDScreen* screen);

This function pulls all the used pins low. This should be called after program flow reaches the end in order to full shut down the display. This does NOT discard the pin configuration!

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void sendCommand(LCDScreen* screen, uint8_t command);

Sends a command to the LCD screen. If a command takes parameters, you can supply them by bitwise ORing them with the command name:

• SCREEN_CLEAR clears the display. Use clearScreen() instead.

• CURSOR_RETURN sets the cursor to (0, 0). Use cursorReturn() instead.

• INPUT_SET sets the writing direction. Use setWritingDirection() instead.

  • Either LEFT_TO_RIGHT or RIGHT_TO_LEFT

• DISPLAY_SWITCH can turn the display on/off and change the cursor style. Use setDisplaySettings() instead.

  • DISPLAY_ON / DISPLAY_OFF
  • CURSOR_ON / CURSOR_OFF
  • CURSOR_BLINK / CURSOR_STATIC

• SHIFT shifts either the cursor or the entire display. Use shiftCursor() or shiftScreen() instead.

  • DISPLAY_SHIFT / CURSOR_SHIFT
  • RIGHT_SHIFT / LEFT_SHIFT

• FUNCTION_SET if you're using this you're using this library wrong

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void sendData(LCDScreen* screen, uint8_t data);

This function sends character data to the screen in order to be displayed. data can be an ASCII char (sendData(&screen, 'H')), or one of the many macros defined in the header file (sendData(&screen, CURRENCY_YEN)).

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void sendText(LCDScreen* screen, const char* text);

This function can send entire strings to the screen. It even supports the special characters! You can put them directly in the string and the function will handle it.

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void sendChars(LCDScreen* screen, unsigned int len, ...);

This function sends a variable number of characters to the screen. Use sendText() instead.

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void loadCustomChar(LCDScreen* screen, uint8_t cgram_addr, ...);

This function writes a custom character into the CGRAM of the LCD screen. cgram_addr can be any number from 0x0 to 0xF. Hence you can have up to 16 custom characters at once in memory.

After the address the function expects 8 bytes of character data. The lower 5 bits encode the pixel data, where 0 stands for black and 1 for white.

After loading a character you can write it by using the CGRAM address as a character byte for the sendData function (e.g. sendData(&screen, 0) will send the character at CGRAM address 0x0).

WARNING: Writing to CGRAM moves the cursor, so keep that in mind when you try to write characters to memory.

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void clearScreen(LCDScreen* screen);

This function clears the screen

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void returnCursor(LCDScreen* screen);

This function sets the cursor position to (0, 0)

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void setWritingDirection(LCDScreen* screen, direction);

This function sets the writing direction of the display. Can either be LEFT_TO_RIGHT or RIGHT_TO_LEFT.

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void shiftCursor(LCDScreen* screen, direction);

This function shifts the cursor in the specified direction. RIGHT_SHIFT or LEFT_SHIFT.

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void shiftScreen(LCDScreen* screen, direction);

This function shifts the entire screen in the specified direction. RIGHT_SHIFT or LEFT_SHIFT.

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void setCursor(LCDScreen* screen, x, y);

This function sets the cursor position on the display.