04-TFT.md

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TFT

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 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"

However in the Embed C Environment, you cannot direct access to the console of the C runtime and connect it to debugger is not always possible and is troublesome indeed. (Experience tell that debug the debugger is a painful experience)

Therefore, we would like to make use of TFT (aka a small LCD monitor), to provide ourselves places to print out our variable and make our life easiler.

Using the TFT

tft_init

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

//Usage
/* main.c*/
/* USER CODE BEGIN 2 */
tft_init(PIN_ON_TOP, BLACK, WHITE, YELLOW, DARK_GREEN);
/* USER CODE END 2 */

Parameter Detail

• 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:

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

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
    }
}

Classwork 2: TFT

• Print the time elapsed with the format of mm:ss:sssZ where sssZ means millisecond. e.g. 00:23:109 (@2)
• Toogle the highlight of the text you print every seconds, which means: (@2)
  • 1st second: print normal text
  • 2nd second: print hightlighted text
    • Recall1:

      tft_prints(0, 2, "{Hello World}");  
      // This is a higlighted text
    • Recall2: We define the colour of hightlight in tft_init:

      void tft_init(TFT_ORIENTATION orientation, uint16_t bg_color, uint16_t text_color, uint16_t text_color_sp, uint16_t highlight_color);
  • 3rd second: print normal text

Remember to add the function prototype before you call it.

/* main.c */
/* USER CODE BEGIN PFP */
void tft_classwork(void);
/* USER CODE END PFP */

Hints: Making use of mod and integer division.

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