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evkmimxrt1170_12_BlitRect

Create an offscreen storing ten numbers, then blit its four rectangles to the upper left corner of display that has a white background, to show four black numbers: "2986".

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 BlitRect.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.

In addition, files of Numbas.h and Numbas.c are used to store numbers of 0-9, whose visual image is CenturyNumbas.png (the background is transparent).

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

    vg_lite_init(64, 64);

  • 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.

In the initialization of this project, a customized load_glyphatlas function configures the vg_lite_buffer_t structure glyphBuffer, and copis line by line from the image data array Numbas_Bitmap0 to this buffer. This process is achieved by the following key code, where glyphBuffer.stride = the byte number per pixel of glyphBuffer.format * glyphBuffer.width

glyphBuffer.width = 160;
glyphBuffer.height = 92;
glyphBuffer.format = VG_LITE_RGBA8888;
error = vg_lite_allocate(&glyphBuffer);

uint8_t * buffer_memory = (uint8_t *) glyphBuffer.memory;
uint8_t  *pdata = (uint8_t *) Numbas_Bitmap0;

for (int j = 0; j < glyphBuffer.height; j++) 
{
    memcpy(buffer_memory, pdata, glyphBuffer.stride);
    buffer_memory += glyphBuffer.stride;
    pdata += glyphBuffer.stride;
}

Drawing Task

Since there is no path to be drawn, the array pathData and vg_lite_path_t structure is not used in this project.

In drawing task, there are following functions:

  • vg_lite_clear clears the render buffer with a solid color (ABGR format).

    In this project, the full screen is filled with white color by

    vg_lite_clear(rt, NULL, 0xFFFFFFFF);

  • 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_translate translates draw result by input coordinates with transformation matrix.

  • vg_lite_blit_rect blits the specified rectangle area of the buffer instead of a whole area like vg_lite_blit_rect.

In this project, the rectangles of four numbers are blit by calling vg_lite_blit_rect function four times, as the input array rect includes the coordinate and size of specified rectangle: rect[0]/[1]/[2]/[3] are x, y, width, and height of the source rectangle respectively. The key code is:

vg_lite_identity(&matrix);
rect[0] = 32; rect[1] = 0; rect[2] = 32; rect[3] = 46;
error = vg_lite_blit_rect(rt, &glyphBuffer, rect, &matrix, VG_LITE_BLEND_SRC_OVER, 0, mainFilter);

vg_lite_translate(34,0,&matrix);
rect[0] = 96; rect[1] = 46; rect[2] = 32; rect[3] = 46;
error = vg_lite_blit_rect(rt, &glyphBuffer, rect, &matrix, VG_LITE_BLEND_SRC_OVER, 0, mainFilter);

vg_lite_translate(34,0,&matrix);
rect[0] = 64; rect[1] = 46; rect[2] = 32; rect[3] = 46;
error = vg_lite_blit_rect(rt, &glyphBuffer, rect, &matrix, VG_LITE_BLEND_SRC_OVER, 0, mainFilter);

vg_lite_translate(34,0,&matrix);
rect[0] = 0; rect[1] = 46; rect[2] = 32; rect[3] = 46;
error = vg_lite_blit_rect(rt, &glyphBuffer, rect, &matrix, VG_LITE_BLEND_SRC_OVER, 0, mainFilter);

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

  • 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_12_BlitRect

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