轉(zhuǎn)自：http://lauri.xn–vsandi-pxa.com/hdl/zynq/zybo-ov7670-to-vga.html

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Piping OV7670 video to VGA output on ZYBO10. Nov ‘14

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Introduction

Before getting into more complex topics such as AXI Stream and direct memory access, it’s recommended to first get familiar with pixel data encoding schemes and video timing signals. Hamsterworks has great examples for Zynq boards [1]. In this example VGA frames are grabbed from OV7670 chipset based camera and stored in Block RAM based framebuffer.

Omnivision OV7670 is a cheap 640x480 30fps camera module.

ZYBO is however more resource constrained so several modifications were required. In this case we’re reducing the vertical resolution twofold since ZYBO does not have enough Block RAM to contain whole VGA frame. The example is basically working on ZYBO, but there are still few bugs that need to be ironed out.

[1] http://hamsterworks.co.nz/mediawiki/index.php/OV7670_camera

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Capture block

The capture block parses VSYNC and HREF signals and converts them into block RAM address. Pixel data is also a bit tricky - OV7670 transmits half of an 16-bit RGB (5:6:5) pixel during one PCLK cycle. Capture block latches the previous half and combines two halves into 12-bit RGB (4:4:4) pixel which is stored in block RAM. You are encouraged to use logic analyzer to debug video timing signals, as connecting wires to VGA output while display is connected is troublesome you might have to route extra pins onto Pmod connectors for debugging purposes.

---------------------------------------------------------------------------------- -- Engineer: Mike Field <hamster@snap.net.nz> -- -- Description: Captures the pixels coming from the OV7670 camera and -- Stores them in block RAM ---------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.ALL; use ieee.NUMERIC_STD.ALL;entity ov7670_capture isport (pclk : in std_logic;vsync : in std_logic;href : in std_logic;d : in std_logic_vector ( 7 downto 0);addr : out std_logic_vector (17 downto 0);dout : out std_logic_vector (11 downto 0);we : out std_logic); end ov7670_capture;architecture behavioral of ov7670_capture issignal d_latch : std_logic_vector(15 downto 0) := (others => '0');signal address : std_logic_vector(18 downto 0) := (others => '0');signal address_next : std_logic_vector(18 downto 0) := (others => '0');signal wr_hold : std_logic_vector( 1 downto 0) := (others => '0');beginaddr <= address(18 downto 1);process(pclk)beginif rising_edge(pclk) then-- This is a bit tricky href starts a pixel transfer that takes 3 cycles-- Input | state after clock tick-- href | wr_hold d_latch d we address address_next-- cycle -1 x | xx xxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxx x xxxx xxxx-- cycle 0 1 | x1 xxxxxxxxRRRRRGGG xxxxxxxxxxxxxxxx x xxxx addr-- cycle 1 0 | 10 RRRRRGGGGGGBBBBB xxxxxxxxRRRRRGGG x addr addr-- cycle 2 x | 0x GGGBBBBBxxxxxxxx RRRRRGGGGGGBBBBB 1 addr addr+1if vsync = '1' thenaddress <= (others => '0');address_next <= (others => '0');wr_hold <= (others => '0');else-- This should be a different order, but seems to be GRB!dout <= d_latch(15 downto 12) & d_latch(10 downto 7) & d_latch(4 downto 1);address <= address_next;we <= wr_hold(1);wr_hold <= wr_hold(0) & (href and not wr_hold(0));d_latch <= d_latch( 7 downto 0) & d;if wr_hold(1) = '1' thenaddress_next <= std_logic_vector(unsigned(address_next)+1);end if;end if;end if;end process; end behavioral;

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Video output block

VGA output block generates HSYNC and VSYNC signals for the video outputs and corresponding input for the read address.

---------------------------------------------------------------------------------- -- Engineer: Mike Field <hamster@snap.net.nz> -- -- Description: Generate analog 640x480 VGA, double-doublescanned from 19200 bytes of RAM -- ---------------------------------------------------------------------------------- library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.NUMERIC_STD.ALL;entity ov7670_vga isport (clk25 : in STD_LOGIC;vga_red : out STD_LOGIC_VECTOR(4 downto 0);vga_green : out STD_LOGIC_VECTOR(5 downto 0);vga_blue : out STD_LOGIC_VECTOR(4 downto 0);vga_hsync : out STD_LOGIC;vga_vsync : out STD_LOGIC;frame_addr : out STD_LOGIC_VECTOR(17 downto 0);frame_pixel : in STD_LOGIC_VECTOR(11 downto 0)); end ov7670_vga;architecture Behavioral of ov7670_vga is-- Timing constantsconstant hRez : natural := 640;constant hStartSync : natural := 640+16;constant hEndSync : natural := 640+16+96;constant hMaxCount : natural := 800;constant vRez : natural := 480;constant vStartSync : natural := 480+10;constant vEndSync : natural := 480+10+2;constant vMaxCount : natural := 480+10+2+33;constant hsync_active : std_logic := '0';constant vsync_active : std_logic := '0';signal hCounter : unsigned( 9 downto 0) := (others => '0');signal vCounter : unsigned( 9 downto 0) := (others => '0');signal address : unsigned(18 downto 0) := (others => '0');signal blank : std_logic := '1';beginframe_addr <= std_logic_vector(address(18 downto 1));process(clk25)beginif rising_edge(clk25) then-- Count the lines and rowsif hCounter = hMaxCount-1 thenhCounter <= (others => '0');if vCounter = vMaxCount-1 thenvCounter <= (others => '0');elsevCounter <= vCounter+1;end if;elsehCounter <= hCounter+1;end if;if blank = '0' thenvga_red <= frame_pixel(11 downto 8) & "0";vga_green <= frame_pixel( 7 downto 4) & "00";vga_blue <= frame_pixel( 3 downto 0) & "0";elsevga_red <= (others => '0');vga_green <= (others => '0');vga_blue <= (others => '0');end if;if vCounter >= vRez thenaddress <= (others => '0');blank <= '1';elseif hCounter < 640 thenblank <= '0';address <= address+1;elseblank <= '1';end if;end if;-- Are we in the hSync pulse? (one has been added to include frame_buffer_latency)if hCounter > hStartSync and hCounter <= hEndSync thenvga_hSync <= hsync_active;elsevga_hSync <= not hsync_active;end if;-- Are we in the vSync pulse?if vCounter >= vStartSync and vCounter < vEndSync thenvga_vSync <= vsync_active;elsevga_vSync <= not vsync_active;end if;end if;end process; end Behavioral;

It essentially plays the role of video card in a PC.

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Controller block

Omnivision OV7670 uses Omnivision Serial Camera Control Bus (SCCB) protocol to set up the camera parameters. SCCB actually is I2C-compliant interface, but avoids the usage of I2C brand due to licensing fees [2]. The controller component is composed of three components: I2C bus master, OV7670 instructions and glue code.

The first one is used to emulate I2C bus master:

---------------------------------------------------------------------------------- -- Engineer: <mfield@concepts.co.nz -- -- Description: Send the commands to the OV7670 over an I2C-like interface ----------------------------------------------------------------------------------library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all;entity i2c_sender isport (clk : in std_logic;siod : inout std_logic;sioc : out std_logic;taken : out std_logic;send : in std_logic;id : in std_logic_vector(7 downto 0);reg : in std_logic_vector(7 downto 0);value : in std_logic_vector(7 downto 0)); end i2c_sender;architecture behavioral of i2c_sender is-- this value gives a 254 cycle pause before the initial frame is sentsignal divider : unsigned (7 downto 0) := "00000001";signal busy_sr : std_logic_vector(31 downto 0) := (others => '0');signal data_sr : std_logic_vector(31 downto 0) := (others => '1'); beginprocess(busy_sr, data_sr(31))beginif busy_sr(11 downto 10) = "10" orbusy_sr(20 downto 19) = "10" orbusy_sr(29 downto 28) = "10" thensiod <= 'Z';elsesiod <= data_sr(31);end if;end process;process(clk)beginif rising_edge(clk) thentaken <= '0';if busy_sr(31) = '0' thenSIOC <= '1';if send = '1' thenif divider = "00000000" thendata_sr <= "100" & id & '0' & reg & '0' & value & '0' & "01";busy_sr <= "111" & "111111111" & "111111111" & "111111111" & "11";taken <= '1';elsedivider <= divider+1; -- this only happens on powerupend if;end if;elsecase busy_sr(32-1 downto 32-3) & busy_sr(2 downto 0) iswhen "111"&"111" => -- start seq #1case divider(7 downto 6) iswhen "00" => SIOC <= '1';when "01" => SIOC <= '1';when "10" => SIOC <= '1';when others => SIOC <= '1';end case;when "111"&"110" => -- start seq #2case divider(7 downto 6) iswhen "00" => SIOC <= '1';when "01" => SIOC <= '1';when "10" => SIOC <= '1';when others => SIOC <= '1';end case;when "111"&"100" => -- start seq #3case divider(7 downto 6) iswhen "00" => SIOC <= '0';when "01" => SIOC <= '0';when "10" => SIOC <= '0';when others => SIOC <= '0';end case;when "110"&"000" => -- end seq #1case divider(7 downto 6) iswhen "00" => SIOC <= '0';when "01" => SIOC <= '1';when "10" => SIOC <= '1';when others => SIOC <= '1';end case;when "100"&"000" => -- end seq #2case divider(7 downto 6) iswhen "00" => SIOC <= '1';when "01" => SIOC <= '1';when "10" => SIOC <= '1';when others => SIOC <= '1';end case;when "000"&"000" => -- Idlecase divider(7 downto 6) iswhen "00" => SIOC <= '1';when "01" => SIOC <= '1';when "10" => SIOC <= '1';when others => SIOC <= '1';end case;when others =>case divider(7 downto 6) iswhen "00" => SIOC <= '0';when "01" => SIOC <= '1';when "10" => SIOC <= '1';when others => SIOC <= '0';end case;end case;if divider = "11111111" thenbusy_sr <= busy_sr(32-2 downto 0) & '0';data_sr <= data_sr(32-2 downto 0) & '1';divider <= (others => '0');elsedivider <= divider+1;end if;end if;end if;end process; end behavioral;

The second one contains OV7670 setup instructions:

-- Company: -- Engineer: Mike Field <hamster@sanp.net.nz> -- -- Description: Register settings for the OV7670 Caamera (partially from OV7670.c -- in the Linux Kernel -- Edited by : Christopher Wilson <wilson@chrec.org> ------------------------------------------------------------------------------------ -- -- Notes: -- 1) Regarding the WITH SELECT Statement: -- WITH sreg(sel) SELECT -- finished <= '1' when x"FFFF", -- '0' when others; -- This means the transfer is finished the first time sreg ends up as "FFFF", -- I.E. Need Sequential Addresses in the below case statements -- -- Common Debug Issues: -- -- Red Appearing as Green / Green Appearing as Pink -- Solution: Register Corrections Below -- -- library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.NUMERIC_STD.ALL;entity ov7670_registers isPort ( clk : in STD_LOGIC;resend : in STD_LOGIC;advance : in STD_LOGIC;command : out std_logic_vector(15 downto 0);finished : out STD_LOGIC); end ov7670_registers;architecture Behavioral of ov7670_registers issignal sreg : std_logic_vector(15 downto 0);signal address : std_logic_vector(7 downto 0) := (others => '0'); begincommand <= sreg;with sreg select finished <= '1' when x"FFFF", '0' when others;process(clk)beginif rising_edge(clk) thenif resend = '1' thenaddress <= (others => '0');elsif advance = '1' thenaddress <= std_logic_vector(unsigned(address)+1);end if;case address iswhen x"00" => sreg <= x"1280"; -- COM7 Resetwhen x"01" => sreg <= x"1280"; -- COM7 Resetwhen x"02" => sreg <= x"1204"; -- COM7 Size & RGB outputwhen x"03" => sreg <= x"1100"; -- CLKRC Prescaler - Fin/(1+1)when x"04" => sreg <= x"0C00"; -- COM3 Lots of stuff, enable scaling, all others offwhen x"05" => sreg <= x"3E00"; -- COM14 PCLK scaling offwhen x"06" => sreg <= x"8C00"; -- RGB444 Set RGB formatwhen x"07" => sreg <= x"0400"; -- COM1 no CCIR601when x"08" => sreg <= x"4010"; -- COM15 Full 0-255 output, RGB 565when x"09" => sreg <= x"3a04"; -- TSLB Set UV ordering, do not auto-reset windowwhen x"0A" => sreg <= x"1438"; -- COM9 - AGC Cellingwhen x"0B" => sreg <= x"4f40"; --x"4fb3"; -- MTX1 - colour conversion matrixwhen x"0C" => sreg <= x"5034"; --x"50b3"; -- MTX2 - colour conversion matrixwhen x"0D" => sreg <= x"510C"; --x"5100"; -- MTX3 - colour conversion matrixwhen x"0E" => sreg <= x"5217"; --x"523d"; -- MTX4 - colour conversion matrixwhen x"0F" => sreg <= x"5329"; --x"53a7"; -- MTX5 - colour conversion matrixwhen x"10" => sreg <= x"5440"; --x"54e4"; -- MTX6 - colour conversion matrixwhen x"11" => sreg <= x"581e"; --x"589e"; -- MTXS - Matrix sign and auto contrastwhen x"12" => sreg <= x"3dc0"; -- COM13 - Turn on GAMMA and UV Auto adjustwhen x"13" => sreg <= x"1100"; -- CLKRC Prescaler - Fin/(1+1)when x"14" => sreg <= x"1711"; -- HSTART HREF start (high 8 bits)when x"15" => sreg <= x"1861"; -- HSTOP HREF stop (high 8 bits)when x"16" => sreg <= x"32A4"; -- HREF Edge offset and low 3 bits of HSTART and HSTOPwhen x"17" => sreg <= x"1903"; -- VSTART VSYNC start (high 8 bits)when x"18" => sreg <= x"1A7b"; -- VSTOP VSYNC stop (high 8 bits)when x"19" => sreg <= x"030a"; -- VREF VSYNC low two bitswhen x"1A" => sreg <= x"0e61"; -- COM5(0x0E) 0x61when x"1B" => sreg <= x"0f4b"; -- COM6(0x0F) 0x4Bwhen x"1C" => sreg <= x"1602"; --when x"1D" => sreg <= x"1e37"; -- MVFP (0x1E) 0x07 -- FLIP AND MIRROR IMAGE 0x3xwhen x"1E" => sreg <= x"2102";when x"1F" => sreg <= x"2291";when x"20" => sreg <= x"2907";when x"21" => sreg <= x"330b";when x"22" => sreg <= x"350b";when x"23" => sreg <= x"371d";when x"24" => sreg <= x"3871";when x"25" => sreg <= x"392a";when x"26" => sreg <= x"3c78"; -- COM12 (0x3C) 0x78when x"27" => sreg <= x"4d40";when x"28" => sreg <= x"4e20";when x"29" => sreg <= x"6900"; -- GFIX (0x69) 0x00when x"2A" => sreg <= x"6b4a";when x"2B" => sreg <= x"7410";when x"2C" => sreg <= x"8d4f";when x"2D" => sreg <= x"8e00";when x"2E" => sreg <= x"8f00";when x"2F" => sreg <= x"9000";when x"30" => sreg <= x"9100";when x"31" => sreg <= x"9600";when x"32" => sreg <= x"9a00";when x"33" => sreg <= x"b084";when x"34" => sreg <= x"b10c";when x"35" => sreg <= x"b20e";when x"36" => sreg <= x"b382";when x"37" => sreg <= x"b80a";when others => sreg <= x"ffff";end case;end if;end process; end Behavioral;

Third one contains glue code for the IP core that can actually be instantiated:

---------------------------------------------------------------------------------- -- Engineer: Mike Field <hamster@snap.net.nz> -- -- Description: Controller for the OV760 camera - transferes registers to the -- camera over an I2C like bus ---------------------------------------------------------------------------------- library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.NUMERIC_STD.ALL;entity ov7670_controller isPort ( clk : in STD_LOGIC;resend :in STD_LOGIC;config_finished : out std_logic;sioc : out STD_LOGIC;siod : inout STD_LOGIC;reset : out STD_LOGIC;pwdn : out STD_LOGIC;xclk : out STD_LOGIC ); end ov7670_controller;architecture Behavioral of ov7670_controller isCOMPONENT ov7670_registersPORT(clk : IN std_logic;advance : IN std_logic;resend : in STD_LOGIC;command : OUT std_logic_vector(15 downto 0);finished : OUT std_logic);END COMPONENT;COMPONENT i2c_senderPORT(clk : IN std_logic;send : IN std_logic;taken : out std_logic;id : IN std_logic_vector(7 downto 0);reg : IN std_logic_vector(7 downto 0);value : IN std_logic_vector(7 downto 0);siod : INOUT std_logic;sioc : OUT std_logic);END COMPONENT;signal sys_clk : std_logic := '0';signal command : std_logic_vector(15 downto 0);signal finished : std_logic := '0';signal taken : std_logic := '0';signal send : std_logic;constant camera_address : std_logic_vector(7 downto 0) := x"42"; -- 42"; -- Device write ID - see top of page 11 of data sheet beginconfig_finished <= finished;send <= not finished;Inst_i2c_sender: i2c_sender PORT MAP(clk => clk,taken => taken,siod => siod,sioc => sioc,send => send,id => camera_address,reg => command(15 downto 8),value => command(7 downto 0));reset <= '1'; -- Normal modepwdn <= '0'; -- Power device upxclk <= sys_clk;Inst_ov7670_registers: ov7670_registers PORT MAP(clk => clk,advance => taken,command => command,finished => finished,resend => resend);process(clk)beginif rising_edge(clk) thensys_clk <= not sys_clk;end if;end process; end Behavioral;

[2] http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/99/t/6092

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Importing VHDL code

To insert VHDL code snippets into Vivado:

• From the main menu select Tools → Create and Package IP, click Next.
• Select Package a specified directory, click Next.
• Locate the directory which contains VHDL files for IP location, click
  Next.
• Set Project name to main component name.
• Set Project location to the parent folder of the VHDL files.
• Click Finish

Once you have added everything to the library it’s time to instantiate the code in the design, for each component add the corresponding block:

• Click on Open Block Design under IP Integrator to open up the high
  level block design.
• Right click in the designer area and select Add IP…
• Locate the components added earlier
• Repeat same steps for all components

Next step is to insert block RAM, clocking wizard and connect the components.

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Instantiating block RAM

Since block RAM is highly platform specific a Xilinx block has to be inserted. Right click in the high level design → Add IP… → Block Memory Generator to insert block RAM. Right click on the block → Customize block… opens up the dialog for editing block RAM parameters.

Stand Alone mode makes it possible to generate Simple Dual Port RAM which is essentially memory with write port and read port. Port width refers to amount of bits that can be read/written at once or in other words the size of a memory slot. Port depth refers to count of such slots which translates to address bit width.

Block RAM generator parameters

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Routing pins

The base.xdc important chunks are following:

# Debounce button and config finished LED set_property PACKAGE_PIN R18 [get_ports button_debounce] set_property PACKAGE_PIN M14 [get_ports led_config_finished]# Top JE set_property PACKAGE_PIN H15 [get_ports ov7670_reset] set_property PACKAGE_PIN J16 [get_ports {ov7670_d[1]}] set_property PACKAGE_PIN W16 [get_ports {ov7670_d[3]}] set_property PACKAGE_PIN V12 [get_ports {ov7670_d[5]}]# Bottom JE set_property PACKAGE_PIN Y17 [get_ports ov7670_pwdn] set_property PACKAGE_PIN T17 [get_ports {ov7670_d[0]}] set_property PACKAGE_PIN U17 [get_ports {ov7670_d[2]}] set_property PACKAGE_PIN V13 [get_ports {ov7670_d[4]}]# Top JD set_property PACKAGE_PIN R14 [get_ports {ov7670_d[7]}] set_property PACKAGE_PIN P14 [get_ports ov7670_pclk] set_property PACKAGE_PIN T15 [get_ports ov7670_vsync] set_property PACKAGE_PIN T14 [get_ports ov7670_sioc]# Bottom JD set_property PACKAGE_PIN V18 [get_ports {ov7670_d[6]}] set_property PACKAGE_PIN V17 [get_ports ov7670_xclk] set_property PACKAGE_PIN U15 [get_ports ov7670_href] set_property PACKAGE_PIN U14 [get_ports ov7670_siod]# Red channel of VGA output set_property PACKAGE_PIN M19 [get_ports {RED_O[0]}] set_property PACKAGE_PIN L20 [get_ports {RED_O[1]}] set_property PACKAGE_PIN J20 [get_ports {RED_O[2]}] set_property PACKAGE_PIN G20 [get_ports {RED_O[3]}] set_property PACKAGE_PIN F19 [get_ports {RED_O[4]}]# Green channel of VGA output set_property PACKAGE_PIN H18 [get_ports {GREEN_O[0]}] set_property PACKAGE_PIN N20 [get_ports {GREEN_O[1]}] set_property PACKAGE_PIN L19 [get_ports {GREEN_O[2]}] set_property PACKAGE_PIN J19 [get_ports {GREEN_O[3]}] set_property PACKAGE_PIN H20 [get_ports {GREEN_O[4]}] set_property PACKAGE_PIN F20 [get_ports {GREEN_O[5]}] # Blue channel of VGA output set_property PACKAGE_PIN P20 [get_ports {BLUE_O[0]}] set_property PACKAGE_PIN M20 [get_ports {BLUE_O[1]}] set_property PACKAGE_PIN K19 [get_ports {BLUE_O[2]}] set_property PACKAGE_PIN J18 [get_ports {BLUE_O[3]}] set_property PACKAGE_PIN G19 [get_ports {BLUE_O[4]}]# Horizontal and vertical synchronization of VGA output set_property PACKAGE_PIN P19 [get_ports HSYNC_O] set_property PACKAGE_PIN R19 [get_ports VSYNC_O]# Voltage levels set_property IOSTANDARD LVCMOS33 [get_ports button_debounce] set_property IOSTANDARD LVCMOS33 [get_ports led_config_finished] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_pclk] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_sioc] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_vsync] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_reset] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_pwdn] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_href] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_xclk] set_property IOSTANDARD LVCMOS33 [get_ports ov7670_siod] set_property IOSTANDARD LVCMOS33 [get_ports {ov7670_d[*]}] set_property IOSTANDARD LVCMOS33 [get_ports {RED_O[*]}] set_property IOSTANDARD LVCMOS33 [get_ports {GREEN_O[*]}] set_property IOSTANDARD LVCMOS33 [get_ports {BLUE_O[*]}] set_property IOSTANDARD LVCMOS33 [get_ports HSYNC_O] set_property IOSTANDARD LVCMOS33 [get_ports VSYNC_O]# Magic set_property CLOCK_DEDICATED_ROUTE FALSE [get_nets ov7670_pclk_IBUF]

Using the pin mapping above the camera can be connected cleanly to the board:

Omnivision OV7670 attached to Pmod connectors JD and JE.

Remember to connect GND and 3.3V rails of the ZYBO to cameras GND and 3.3V rails.

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Final high level design

High level design

Click on Generate bitstream button and transfer resulting bitstream file to the boot partition and restart ZYBO.

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Summary

If you’ve connected camera correctly you should see the video feed from the camera on the screen attached to VGA output. Capture and controller blocks can be re-used in other examples involving Omnivision OV7670 camera, so it’s important to get expected outcome at this point.

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