Coordinates

Functions
void	ezLCD_set_xy (int16_t x, int16_t y)
void	ezLCD_set_x (int16_t x)
void	ezLCD_set_y (int16_t y)
void	ezLCD_save_position (uint8_t index)
void	ezLCD_restore_position (uint8_t index)

Detailed Description

This header file is used to manage the coordinates of the current position.

A most drawing functions in this library utilize the current position . The current position can be thought of as a cursor; it indicates the point or starting point where some activity will occur. This value is stored internally on the ezLCD+103 and cannot be read back.

Even though the display is 320 pixels wide by 240 pixels tall, the current position may assume values off of the screen in both the negative and positive direction. This will result in objects being drawn partially or completely off screen.

The coordinate system is rather unconventional in comparison to the standard Cartesian coordinate system. In this coordinate system, Y values increase as one moves south while X values increase as one moves east as they do in the regular Cartesian system. Imagine that the screen takes up a portion of the fourth quadrant of the Cartesian plane; however, we take the absolute value of the Y-coordinate. This concept is illustrated in the image below.

Coordinate System of the ezLCD+103

Function Documentation

void ezLCD_restore_position

(

uint8_t

index

)

This function is used restore the current position from memory.

Parameters

• index = index in memory where the current position should be restored from. This value is in the set of [0, 255].

Assumptions

• The user has previously saved the requested current position using the ezLCD_save_position() function.
• The user has initialized the MCU's SPI interface with the EZLCD_INIT_SPI() macro.
• The user has set the MCU's SPI pins to inputs and outputs appropriately.
  
  
  • SS_BAR = OUTPUT
  • SCK = OUTPUT
  • MOSI = OUTPUT
  • MISO = INPUT

void ezLCD_save_position

(

uint8_t

index

)

This function is used save the current position for later use.

Parameters

• index = index in memory where the current position should be saved. This value is in the set of [0, 255].

Assumptions

• The user has initialized the MCU's SPI interface with the EZLCD_INIT_SPI() macro.
• The user has set the MCU's SPI pins to inputs and outputs appropriately.
  
  
  • SS_BAR = OUTPUT
  • SCK = OUTPUT
  • MOSI = OUTPUT
  • MISO = INPUT

void ezLCD_set_x

(

int16_t

x

)

This function is used to set the X coordinate of the current position .

Parameters

• x = X coordinate value in the set of [-32768, 32767].

Assumptions

• The user has initialized the MCU's SPI interface with the EZLCD_INIT_SPI() macro.
• The user has set the MCU's SPI pins to inputs and outputs appropriately.
  
  
  • SS_BAR = OUTPUT
  • SCK = OUTPUT
  • MOSI = OUTPUT
  • MISO = INPUT

void ezLCD_set_xy	(	int16_t	x,
		int16_t	y
	)

This function is used to set the XY coordinates of the current position.

Parameters

• x = X coordinate value in the set of [-32768, 32767].
• y = Y coordinate value in the set of [-32768, 32767].

Assumptions

• The user has initialized the MCU's SPI interface with the EZLCD_INIT_SPI() macro.
• The user has set the MCU's SPI pins to inputs and outputs appropriately.
  
  
  • SS_BAR = OUTPUT
  • SCK = OUTPUT
  • MOSI = OUTPUT
  • MISO = INPUT

void ezLCD_set_y

(

int16_t

y

)

This function is used to set the Y coordinate of the current position .

Parameters

• y = Y coordinate value in the set of [-32768, 32767].

Assumptions

• The user has initialized the MCU's SPI interface with the EZLCD_INIT_SPI() macro.
• The user has set the MCU's SPI pins to inputs and outputs appropriately.
  
  
  • SS_BAR = OUTPUT
  • SCK = OUTPUT
  • MOSI = OUTPUT
  • MISO = INPUT