Drawing a triangle

Questions » Drawing a triangle

Alyx McCown

4 years, 5 months ago.

I need to draw a triangle, i found in the stm32746g_discovery_lcd.h

stm32746g_discovery_lcd.h line 227

 BSP_LCD_DrawPolygon(pPoint Points, uint16_t PointCount);

and i have no idea how i would set that up, i found in the stm32746g_discovery_lcd.c file where it references and the code is as follows.

stm32746g_discovery_lcd.c line 956

void BSP_LCD_DrawPolygon(pPoint Points, uint16_t PointCount)
{
  int16_t x = 0, y = 0;
  
  if(PointCount < 2)
  {
    return;
  }
  
  BSP_LCD_DrawLine(Points->X, Points->Y, (Points+PointCount-1)->X, (Points+PointCount-1)->Y);
  
  while(--PointCount)
  {
    x = Points->X;
    y = Points->Y;
    Points++;
    BSP_LCD_DrawLine(x, y, Points->X, Points->Y);
  }
}

I remember learning about the arrow operators and how they typically reference unions or arrays or something like that but i can't for the life of me remember exactly how to create what it needs. (and embarrassingly enough i remember this being the primary subject for nearly 3 days of classes)

Would someone please mind explaining this to me? or in the very least set up a simple 3 point triangle of some random coordinates for me to use as a reference? Thank you!

PS: BSP_LCD_FillPolygon would also work, but appears similar

Question relating to:

Last updated: 20 Apr 2021

DISCO-F746NG

The STM32F746G-DISCO discovery board (32F746GDISCOVERY) is a complete demonstration and development platform for STMicroelectronics ARM® Cortex®-M7 core-based STM32F746NGH6 microcontroller.

1 Answer

Jan Kamidra

4 years, 5 months ago.

Hi there,

you need to follow the comments above the function

Quote:

/**

@brief Draws an poly-line (between many points).
@param Points: Pointer to the points array
@param PointCount: Number of points
@retval None
/

So you need an array of coordinates and when you will look into parameters of the BSP_LCD_DrawPolygon(point Points, uint16_t PointCount); a struct of Point must exist.

One struct of stm32746g_discovery_lcd.c

typedef struct 
{
  int16_t X;
  int16_t Y;
}Point, * pPoint;

So you need to add something like this, for example.

        Point p[3]; // tringle = 3 points = 3x struct of coordinates 
        p[0].X = 240;   p[0].Y = 20;  
        p[1].X = 200;   p[1].Y = 100; 
        p[2].X = 280;   p[2].Y = 100;
        BSP_LCD_SetTextColor(LCD_COLOR_RED);
        BSP_LCD_DrawPolygon(p, 3);

You can simple copy & paste it into ST example, between lines 32-33.

Import program DISCO-F746NG_LCD_demo

Basic example showing how to drive the LCD.

BR, Jan

Alyx McCown

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4 years, 5 months ago.