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1. VGA概述
VGA(Video Graphics Array)是IBM在1987年推出的一種視頻傳輸,具有分辨率高、顯示速率快、顏色豐富等優(yōu)點(diǎn),在彩色顯示器領(lǐng)域得到了廣泛的應(yīng)用。不支持熱插拔,不支持音頻傳輸。
2. VGA時(shí)序
下面以640*480@60Hz為例說(shuō)明VGA時(shí)序和FPGA設(shè)計(jì),其他分辨率和幀率的可參考VESA中查找。
計(jì)算像素時(shí)鐘pclk = 800*525*60 = 25200000,注意這里的HSYNC和VSYNC都是低電平有效,且HSYNC在數(shù)據(jù)行無(wú)效區(qū)域也要提供。
3. VGA電路圖
電路以ADV7123為例:
4. FPGA邏輯代碼
//------------Video Test--------------- parameter IMG_HDISP =16'd640; parameter IMG_VDISP = 16'd480; wire pclk; assign pclk = clk_25m; //VIDEO input reg [15:0] vcnt; reg [11:0] hcnt; reg vsync; reg hsync; reg [7:0] data; reg data_valid; always @(posedge pclk) if(hcnt>=(IMG_HDISP+159)) hcnt <= 0; else hcnt <= hcnt + 1'b1; always @(posedge pclk) if(hcnt>=(IMG_HDISP+159)) if(vcnt>=(IMG_VDISP+44)) vcnt <= 0; else vcnt <= vcnt + 1'b1; else vcnt <= vcnt; always @(posedge pclk) if((hcnt>=IMG_HDISP+16) & (hcnt<(IMG_HDISP+96)))// & (vcnt>=0) & (vcnt<(IMG_VDISP))) hsync <= 1'b1; else hsync <= 1'b0; always @(posedge pclk) if(vcnt>=(IMG_VDISP+9) & vcnt<(IMG_VDISP+11)) vsync <= 1'b1; else vsync <= 1'b0; always @(posedge pclk) if((hcnt>=0) & (hcnt<(IMG_HDISP)) & (vcnt>=0) & (vcnt<(IMG_VDISP))) data_valid <= 1'b1; else data_valid <= 1'b0; always @(posedge pclk) if(vsync) data <= 0; else if((hcnt>=0) & (hcnt<(IMG_HDISP)) & (vcnt>=0) & (vcnt<(IMG_VDISP/4))) // data <= data + 1'b1; if(hcnt>=0 & hcnt<(IMG_HDISP/4)) data <= 8'h00; else if(hcnt>=(IMG_HDISP/4) & hcnt<(2*IMG_HDISP/4)) data <= 8'hff; else if(hcnt>=(2*IMG_HDISP/4) & hcnt<(3*IMG_HDISP/4)) data <= 8'h00; else data <= 8'hff; else if((hcnt>=0) & (hcnt<(IMG_HDISP)) & (vcnt>=(IMG_VDISP/4)) & (vcnt<(2*IMG_VDISP/4))) if(hcnt>=0 & hcnt<(IMG_HDISP/4)) data <= 8'hff; else if(hcnt>=(IMG_HDISP/4) & hcnt<(2*IMG_HDISP/4)) data <= 8'h00; else if(hcnt>=(2*IMG_HDISP/4) & hcnt<(3*IMG_HDISP/4)) data <= 8'hff; else data <= 8'h00; // data <= data + 1'b1; else if((hcnt>=0) & (hcnt<(IMG_HDISP)) & (vcnt>=(2*IMG_VDISP/4)) & (vcnt<(3*IMG_VDISP/4))) if(hcnt>=0 & hcnt<(IMG_HDISP/4)) data <= 8'h00; else if(hcnt>=(IMG_HDISP/4) & hcnt<(2*IMG_HDISP/4)) data <= 8'hff; else if(hcnt>=(2*IMG_HDISP/4) & hcnt<(3*IMG_HDISP/4)) data <= 8'h00; else data <= 8'hff; // data <= data + 1'b1; else if((hcnt>=0) & (hcnt<(IMG_HDISP)) & (vcnt>=(3*IMG_VDISP/4)) & (vcnt<(IMG_VDISP))) // data <= data + 1'b1; if(hcnt>=0 & hcnt<(IMG_HDISP/4)) data <= 8'hff; else if(hcnt>=(IMG_HDISP/4) & hcnt<(2*IMG_HDISP/4)) data <= 8'h00; else if(hcnt>=(2*IMG_HDISP/4) & hcnt<(3*IMG_HDISP/4)) data <= 8'hff; else data <= 8'h00; else data <= 0; assign lcd_vs = ~vsync; assign lcd_hs = ~hsync; assign vga_red = data; assign vga_green = data; assign vga_blue = data; assign lcd_dclk = clk_25m; assign lcd_blank = 1'b1; assign lcd_sync = 1'b0; wire [7:0] vga_red; wire [7:0] vga_green; wire [7:0] vga_blue; assign lcd_red[9:2] = vga_red; assign lcd_green[9:2] = vga_green; assign lcd_blue[9:2] = vga_blue;
5.演示結(jié)果
下圖為方格顯示效果:
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