Reflet GPU

A GPA for FPGAs with a test layer and a bitmap layer.

The top module of the GPU is VGA_base/reflet_VGA.v.

Parameters

The top modules parameters are:

• clk_freq: the input clock frequency in Hertz.
• refresh_rate: the refresh rate in frames per seconds.
• h_size, h_front_porch, h_sync_pulse, h_back_porsh, v_line, v_front_porsh, v_sync_pulse, and v_back_porsh: image parameters, all in pixels.
• color_depth: The number of bit per color channel.
• ram_resetable: Is the ram zeroed with the reset signal?
• bit_reduction: The effective number of pixel displayed is (v_line * h_size) / (2 ^ bit_reduction). Useful to reduce memory usage and high frequency need.

The default are for a 1 MHz clock and a true-color 640x480 picture.

IOs

The top module have the following IOs:

• clk: input clock.
• reset: reset low signal.
• h_pixel and v_pixel: input for the pixel or letter to be edited.
• R_in, G_in, B_in, a_in, R_bg_in, G_bg_in, B_bg_in, and char_in: input color and letter.
• write_bitmap and write_txt: input write command.
• h_sync, v_sync, R_out, G_out, and B_out: VGA signal.

Writing on the screen

Writing a letter

To write on the text layer, choose the letter with char_in. Choose the color of the letter with R_in, G_in, and B_in; and choose the background of the letter with R_bg_in, G_bg_in, and B_bg_in. Choose the position of the letter with h_pixel and v_pixel. This is the position of the letter on the text grid, not on a pixel count. Finally, set write_txt to one for at least a clock cycle.

Writing a pixel

To write a pixel, choose the color with R_in, G_in, and B_in. Choose the transparency with a_in. Choose the position of the pixel with v_pixel and h_pixel. Finally, set write_bitmap to one for at least a clock cycle.

Font used

The text layer uses the font Public Pixel made by GGBotNet under the license Creative Commons Zero v1.0 Universal.

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