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evkmimxrt1170_01_SimplePath

Clear an offscreen with white color and draw a red triangle on it, then blit it to the center of display that has a blue background.

Hardware Preparation

If using the MIPI interface, connect the LCD displayer to J48 on the MIMXRT1170-EVK board. Connect 5V power to J43, set J38 to 1-2, and turn on the power switch SW5.

Software Preparation

Now three LCD displayers are supported, which are defined in display_support.h:

#define DEMO_PANEL_RK055AHD091 0 /* 720 * 1280, RK055AHD091-CTG(RK055HDMIPI4M) */
#define DEMO_PANEL_RK055IQH091 1 /* 540 * 960,  RK055IQH091-CTG */
#define DEMO_PANEL_RK055MHD091 2 /* 720 * 1280, RK055MHD091A0-CTG(RK055HDMIPI4MA0) */

Use the macro DEMO_PANEL to select the LCD panel you are using, the default panel is RK055AHD091-CTG configured in the display_support.h:

#define DEMO_PANEL DEMO_PANEL_RK055AHD091

For example, if your LCD panel is RK055MHD091A0-CTG, change the macro DEMO_PANEL definition as following:

#define DEMO_PANEL DEMO_PANEL_RK055MHD091

The source code is in SimplePath.c, where the main function first configures clocks, pins, etc. freerots is deployed in the example. vglite_task is created and scheduled to execute VGLite initialization and drawing task.

VGLite Initialization

Before drawing, several functions are executed to do initialization:

  • vg_lite_init initializes VGLite and configures the tessellation buffer size, which is recommended to be the size of the most commonly rendered path size. In this project, it's defined by

    #define OFFSCREEN_BUFFER_WIDTH  400
#define OFFSCREEN_BUFFER_HEIGHT 400

error = vg_lite_init(OFFSCREEN_BUFFER_WIDTH, OFFSCREEN_BUFFER_HEIGHT);

  • vg_lite_set_command_buffer_size sets the GPU command buffer size (optional).

  • vg_lite_allocate allocates the render buffer, whose the input parameter is vg_lite_buffer_t structure defining width, height, and color format, etc.

Drawing Task

The path drawing opcodes (1st column) and arguments (other columns) are defined in the array pathData, such as

static int32_t pathData[] = {
    2, 0, 400,    //Move to (0, 400)
    4, 400, 400,  //Line from (0,400) , to (400, 400)
    4, 200, 0,    //Line from (400, 400) to (200, 0)
    4, 0, 400,    //Line from (200, 0) to (0, 400)
    0,
};

And vg_lite_path_t structure describes path data's bounding box, quality, coordinate format, etc., such as

static vg_lite_path_t path = {
    {0, 0,              // left,top
    400, 400},          // right,bottom
    VG_LITE_HIGH,       // quality
    VG_LITE_S32,        // 
    {0},                // uploaded
    sizeof(pathData),   // path length
    pathData,           // path data
    1                   // path changed
};

In drawing task, there are following functions:

  • vg_lite_clear clears the render buffer with a solid color (ABGR format). In this project, the rendered area is filled with white color by

    vg_lite_clear(&renderTarget, NULL, 0xFFFFFFFF);

    And the full screen is filled with blue color by

    vg_lite_clear(rt, NULL, 0xFFFF0000);

  • vg_lite_identity resets the specified transformation matrix, which is uninitialized or previously modified by functions of vg_lite_translate, vg_lite_rotate, vg_lite_scale.

  • vg_lite_draw performs a 2D vector draw operation, drawing input path data with the specified fill rule, transformation matrix, blend mode, and fill color, etc. This project fills the above path with red color by

    error = vg_lite_draw(&renderTarget, &path, VG_LITE_FILL_EVEN_ODD, &matrix, VG_LITE_BLEND_NONE, 0xFF0000FF);

  • vg_lite_translate translates draw result by input coordinates with transformation matrix. The path in this project is moved by

    vg_lite_translate(DEMO_BUFFER_WIDTH/2 - 200, DEMO_BUFFER_HEIGHT/2 - 200, &matrix);

  • vg_lite_blit finally copies the source image to the destination window with the specified blend mode and filter mode, determining the showing of objects. In this project, VG_LITE_BLEND_SRC_OVER blend mode is selected to make source image placed on the background:

    error = vg_lite_blit(rt, &renderTarget, &matrix, VG_LITE_BLEND_SRC_OVER, 0, mainFilter);

Once an error occurs, cleaning work is needed including the following functions:

  • vg_lite_free frees the allocated render buffer.

    vg_lite_free(&renderTarget);

  • vg_lite_clear_path clears path data uploaded to GPU memory.

    vg_lite_clear_path(&path);

  • vg_lite_close finally frees up the entire memory initialized earlier by the vg_lite_init function.

    vg_lite_close();

Run

Compile firstly, and use a Micro-USB cable to connect PC to J86 on MIMXRT1170-EVK board, then download the firmware and run.

If it's successful, the correct image will show on the displayer:

evkmimxrt1170_01_SimplePath

And FPS information will be sent through UART serial port continuously. The correct UART configuration is

  • 115200 baud rate
  • 8 data bits
  • No parity
  • One stop bit
  • No flow control