PCD8544 LCD driver

Driver for PCD8544 LCD displays.

PCD8544_RES_X

pixels per row

(84U)

PCD8544_RES_Y

pixels per column

(48U)

PCD8544_COLS

characters per row

(14U)

PCD8544_ROWS

characters per column

(6U)

PCD8544_DEFAULT_CONTRAST

(45U)

PCD8544_DEFAULT_BIAS

(3U)

PCD8544_DEFAULT_TEMPCOEF

(0U)

int pcd8544_init(pcd8544_t * dev, spi.h::spi_t spi, gpio.h::gpio_t cs, gpio.h::gpio_t reset, gpio.h::gpio_t mode)

Initialize the given display.

Parameters

dev:device descriptor of display to use spi:SPI bus the display is connected to cs:GPIO pin that is connected to the CS pin reset:GPIO pin that is connected to the RESET pin mode:GPIO pin that is connected to the MODE pin

Return values

• 0 on success
• <0 on error

void pcd8544_set_contrast(const pcd8544_t * dev, uint8_t contrast)

Set the contrast for the given display.

Note

A contrast value of 45 yields good results for 3V3

Parameters

dev:display device descriptor contrast:targeted contrast value [0 - 127]

void pcd8544_set_tempcoef(const pcd8544_t * dev, uint8_t coef)

Set the temperature coefficient for the given display.

Note

Look at the datasheet for more information

Parameters

dev:device descriptor of display to use coef:temperature coefficient to use [0 - 3]

void pcd8544_set_bias(const pcd8544_t * dev, uint8_t bias)

Set the internal BIAS for the given display.

Note

Look at the datasheet for more information

Parameters

dev:device descriptor of display to use bias:the BIAS to use [0 - 7]

void pcd8544_write_img(const pcd8544_t * dev, const char img)

Write an image to memory of the given display.

The image must be given as a char array with 504 elements. Each bit in the array represents one pixel on the display. Each byte in the array contains 8 stacked pixels, from top to bottom. So byte[0] contains the pixels from (0,0) to (0,7), byte[1] (1,0) to (1,7) and byte[503] the pixels from (83,40) to (83,47) -> see the ‘horizontal addressing’ section in the datasheet.

Parameters

dev:device descriptor of display to use img:char array with image data (must be of size := 504)

void pcd8544_write_c(const pcd8544_t * dev, uint8_t x, uint8_t y, const char c)

Write a single ASCII character to the display.

The position of the character is specified in columns (x) and rows (y)

Parameters

dev:device descriptor of display to use x:column to put the character [0 - 13] y:row to put the character [0 - 5] c:ASCII code for the character to write

void pcd8544_write_s(const pcd8544_t * dev, uint8_t x, uint8_t y, const char * str)

Write a string to a given position on the display.

This function prints a given string to the given position on the display. The position is given in terms of columns (x) and rows (y). If a string does not fit completely in the given position (it overflows its row), the overflowing part of the string is cut off.

Parameters

dev:device descriptor of display to use x:starting column of the string [0 - 13] y:row to write the string to [0 - 5] str:string to write to the display

void pcd8544_clear(const pcd8544_t * dev)

Clear the current display (clear the display memory)

Parameters

dev:device descriptor of display to use

void pcd8544_invert(pcd8544_t * dev)

Invert the display (toggles dark and bright pixels)

Parameters

dev:device descriptor of display to use

int pcd8544_is_inverted(const pcd8544_t * dev)

Get the current inversion status of the display.

Parameters

dev:device descriptor of display to use

Return values

• 0 -> display is not inverted
• 1 -> display is inverted

void pcd8544_poweron(const pcd8544_t * dev)

Power on the display.

Parameters

dev:device descriptor of display to use

void pcd8544_poweroff(const pcd8544_t * dev)

Poser off the display.

Parameters

dev:device descriptor of display to use

void pcd8544_riot(const pcd8544_t * dev)

I wonder what this does -> find out!

Parameters

dev:device descriptor of display to use

struct pcd8544_t

PCD8544 device descriptor.

spi.h::spi_t spi

SPI bus the display is connected to.

gpio.h::gpio_t cs

chip-select pin, low: active

gpio.h::gpio_t reset

reset pin, low: active

gpio.h::gpio_t mode

mode pin: low: cmd mode, high: data mode

uint8_t inverted

internal flag to keep track of inversion state