TFT

a small robot screen

Authors

Binay Gurung

Modified by: Leo Wong, Christopher Kwan

Printing something

When learning programming, most of the integrated development environment (IDE) you will/might have used will have a console for output and will often be used for debugging for you to keep track of certain variables and to trace-out truth tables or so forth.

In different programming languages, you can print/show your variable's value in the program using print function.

For Example

In C,

int c = 25;
printf("The value of c-squared is : %d",c*c);
//Output will come as "The value of c-squared is : 625"

In Python,

c = 25
print("The value of c-squared is: ",c*c) # c**2
#Output will come as "The value of c-squared is : 625"

In Java,

int c = 25;
System.out.println("The value of c-squared is " + c*c);
//Output will come as "The value of c-squared is : 625"

In our embedded system, usually we do not have a console to output our variable values to when debugging.

However, with the help of TFT (a small LCD monitor), you will be able to "print out" the values of your variable on a monitor.

Initialize TFT

Function Prototype

void tft_init(TFT_ORIENTATION orientation, uint16_t bg_color, uint16_t text_color, uint16_t text_color_sp, uint16_t highlight_color);

Parameters

• orientation - Orientation of the monitor

• bg_color - Background color

• text_color - Text color

• text_color_sp - Special Text color - []

• highlight_color - Highlight color - {}

The parameters have already been defined for you in lcd.h header-file. It is defined as follows:

* Orientation

typedef enum {
    PIN_ON_TOP,
    PIN_ON_LEFT,
    PIN_ON_BOTTOM,
    PIN_ON_RIGHT
} TFT_ORIENTATION;

* Colors

You may choose one of the following colours according to your own desire for the TFT. Of course! You may also define new color yourself. The following are RGB565 format

#define WHITE           (RGB888TO565(0xFFFFFF))
#define BLACK           (RGB888TO565(0x000000))
#define DARK_GREY       (RGB888TO565(0x555555))
#define GREY            (RGB888TO565(0xAAAAAA))
#define RED             (RGB888TO565(0xFF0000))
#define DARK_RED        (RGB888TO565(0x800000))
#define ORANGE          (RGB888TO565(0xFF9900))
#define YELLOW          (RGB888TO565(0xFFFF00))
#define GREEN           (RGB888TO565(0x00FF00))
#define DARK_GREEN      (RGB888TO565(0x00CC00))
#define BLUE            (RGB888TO565(0x0000FF))
#define BLUE2           (RGB888TO565(0x202060))
#define SKY_BLUE        (RGB888TO565(0x11CFFF))
#define CYAN            (RGB888TO565(0x8888FF))
#define PURPLE          (RGB888TO565(0x00AAAA))
#define PINK            (RGB888TO565(0xC71585))
#define GRAYSCALE(S)    (2113*S)

Example:

/*
 * Initialisation Example
 *
 * Orientation : Pin_on_top
 * Background color : black
 * Text color : white
 * Special Text color : red
 * Highlight color : dark green
 */

tft_init(PIN_ON_TOP, BLACK, WHITE, RED, DARK_GREEN);

Print String

void tft_prints(uint8_t x, uint8_t y, const char* fmt, ...);

• x: nth horizontal column ranging from 0 to 15 (16 columns)

• y: nth vertical row, ranging from 0 to 9 (10 rows)

• fmt: string with format templates (same as C's printf)

• ... : variable to replace the placeholder in the string (same as C's printf)

Example

int a = 10;
tft_prints(0, 0, "The value of a is %d", a);
// The value of a is 10

tft_prints(0, 1, "The |underlined| word");
// "underlined" is underlined by a pair of |

tft_prints(0, 2, "Escape [this `[`]]");
// Escape this []
// first pair of [] changes text inside to special text color
// use ` (backtick) to escape the character right after

Print Pixel

void tft_print_pixel(uint16_t color, uint32_t x, uint32_t y);

• color : colour of your pixel (Use the #define colours)

• x : n-th horizontal pixel, ranging from 0 to 127

• y : n-th vertical pixel , ranging from 0 to 159

Update

uint8_t tft_update(uint32_t period);
uint8_t tft_update2(uint32_t period);

// update the screen to print text and colors

• period : period of update in ms

Miscellaneous

void drawLine(int16_t x0, int16_t y0, int16_t x1, int16_t y1, uint16_t color);

void drawCircle(int16_t x0, int16_t y0, int16_t r, uint16_t color);

void drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2, uint16_t color)

Example of using TFT

while(1){
    /*This is referring to your main while(1) loop,
      Do not create another while(1)*/
    if(tft_update(50) == 0){
        tft_prints(0, 0, "Hello World"); // normal
        tft_prints(0, 1, "[Hello World]");  // This is a special text with differnt color
        tft_prints(0, 2, "{Hello World}");  // This is a higlighted text
        tft_prints(0, 3, "|Hello World|");  // This is a underlined text
    }
}

Remember to include the relevant libraries

#include "xxx.h"

FYI: There are some functions that will be useful.