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evkmimxrt1170_19_Font

Draw a paragraph made by Kurt Sievers, President and Chief Executive Officer, NXP. (black text on yellow background, freesans font)

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 Font.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, the freesans.h file stores the data of Freesans font.

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 DEFAULT_VG_LITE_TW_WIDTH                        128 /* pixels */
#define DEFAULT_VG_LITE_TW_HEIGHT                       128 /* pixels */

error = vg_lite_init(DEFAULT_VG_LITE_TW_WIDTH, DEFAULT_VG_LITE_TW_HEIGHT);

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

Two new sturctures, vg_lite_font_params_t and vg_lite_font_attributes_t, appear for configuring the font.

  • vg_lite_font_params_t configures the font parameters such as type (eFontType_t), weight (eFontWeight_t), stretch (eFontStretch_t), style (eFontStyle_t), height, etc.

    static vg_lite_font_params_t font_params = {
    .font_type      = eFontTypeVector,
    .font_weight    = eFontUltraBlack,
    .font_stretch   = eFontStretchNormal,
    .font_style     = eFontStyleNormal,
    .font_height    = 35
};

  • vg_lite_font_attributes_t structure sets the text attributes like alignment (eTextAlign_t), text color, background color, margin, anchor, scale, font height etc.

    static vg_lite_font_attributes_t font_attribs = {
    .justify         = 0,
    .alignment       = eTextAlignLeft,
    .width           = 1200,
    .height          = 50,
    .text_color      = OPAQUE_VGLITE_COLOUR(0, 0, 0), /* black */
    .bg_color        = OPAQUE_VGLITE_COLOUR(0xff, 0xff, 0xff), /* white */
    .tspan_has_dx_dy = 0,
    .margin          = 5,
    .anchor          = 0,
    .scale           = 1,
    .font_height     = 34,
    .last_x          = 0,
    .last_y          = 0,
    .last_dx         = 0
};

The vg_lite_register_font function registers font by prepared structures of vg_lite_font_t and vg_lite_font_params_t.

static vg_lite_font_t font = VG_LITE_INVALID_FONT;

// Register font
strcpy(font_params.name, FONT_NAME);

font_params.data        = freesans_vft;
font_params.data_len    = FONT_VFT_LEN;

error = vg_lite_register_font(&font, &font_params);

Drawing Task

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 cleared by

    vg_lite_clear(rt, NULL, OPAQUE_VGLITE_COLOUR(0xff, 0xa4, 0x48));

  • 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_draw_text is used to draw text, whose input parameters include target buffer, text to be shown, vg_lite_font_t structure, X and Y coordinates, transformation matrix, blend mode, and vg_lite_font_attributes_t structure.

In this project, a paragraph is drawn line by line by the following key code:

vg_lite_identity(&matrix);
vg_lite_translate(50, 100, &matrix);
error = vg_lite_draw_text(rt, "I truly believe NXP will be at the", font, 0, 0, &matrix, VG_LITE_BLEND_SRC_OVER, &font_attribs);

vg_lite_translate(0, 50, &matrix);
error = vg_lite_draw_text(rt, "forefront of technological solutions", font, 0, 0, &matrix, VG_LITE_BLEND_SRC_OVER, &font_attribs);

...
...

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

  • vg_lite_unregister_font frees the allocated memory when font is registered:

    vg_lite_unregister_font(font);

  • 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_19_Font

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