World's worst video card? The exciting conclusion
Ben Eater・2 minutes read
The circuit generates a valid VGA signal for a monitor in 800 by 600 mode using precise timing and color control methods, ensuring correct pixel output and color generation. Despite some technical challenges with the EEPROM causing minor visual glitches, the primary goal was achieved in successfully displaying an image on the monitor, with additional information available on the creator's website.
Insights
- The circuit generates a valid VGA signal by correctly synchronizing horizontal and vertical sync pulses, ensuring compatibility with a monitor in 800 by 600 mode.
- To prevent white outputs during blanking intervals that could damage the monitor, a NAND gate controls the EEPROM's output enable signal, addressing potential issues with pixel output discrepancies and ensuring successful image display.
Get key ideas from YouTube videos. It’s free
Recent questions
How does the circuit generate a valid VGA signal?
The circuit generates a valid VGA signal by producing correct horizontal and vertical sync pulses that are recognized by a monitor in 800 by 600 mode. This is achieved through precise timing of the horizontal sync pulse lasting 3.2 µs and sent 38,000 times per second, along with a 0.1056 ms sync pulse sent 60 times per second. Binary counters ensure the pulse width and frequency match specifications, while another counter counts each screen line from 0 to 628 to align with timing specs and validate the signal. Additional signals for red, green, and blue colors are synchronized with horizontal and vertical counters to track screen painting, with pixel data stored in an EEPROM and retrieved using the counters as addresses.
How are pixel colors determined in the VGA interface?
Pixel colors in the VGA interface are determined based on the monitor position and the signals for red, green, and blue. The red, green, and blue signals, synchronized with the horizontal and vertical counters, indicate the current pixel being painted on the screen. By controlling the amounts of green, red, and blue using resistors connected to the outputs of an EEPROM, 64 different colors can be generated for display on the VGA monitor. Specific voltage levels for each color component are achieved by combining binary data using resistors, allowing for a range of shades and colors to be displayed accurately.
What issue arises with the EEPROM during blanking intervals?
An issue arises where the EEPROM outputs white during blanking intervals, potentially damaging the monitor. This occurs due to the EEPROM's slow speed compared to the monitor's expected pixel rate, causing discrepancies in pixel output. To address this problem, a NAND gate is added to control the output enable signal of the EEPROM during blanking intervals, ensuring that white outputs are prevented and the monitor is protected from potential damage.
How is image data converted for display on the VGA monitor?
Image data is converted for display on the VGA monitor by resizing the image to 100 by 75 pixels and converting it to indexed color mode with a custom palette of 64 colors. A Python script is used to convert the image data into pixel bytes, which are then written to a binary file for the EEPROM. However, due to the EEPROM's access time delay, black vertical lines may appear in the displayed image as a result of invalid pixel outputs. This delay can cause discrepancies in the image output, impacting the overall quality of the displayed image.
What is the primary objective of the video editing process in this context?
The primary objective of the video editing process in this context is to successfully display an image on the VGA monitor. While the video editing process can be accelerated, the video itself may appear slow due to the intricacies involved in generating 64 colors and controlling pixel outputs. The creator's website offers schematics, data sheets, and parts for replicating the process, highlighting the time-intensive nature of producing such videos. Support from patrons enables the creator to continue making content, showcasing the dedication required to achieve successful image display on the VGA monitor.
Related videos
Summary
00:00
"Creating VGA Signal with 64 Colors"
- The circuit generates a valid VGA signal recognized by a monitor in 800 by 600 mode due to correct horizontal and vertical sync pulses.
- Horizontal sync pulse lasts 3.2 µs, sent 38,000 times per second, while a 0.1056 ms sync pulse is sent 60 times per second.
- A binary counter counts from 0 to 264 at 10 million times per second, ensuring pulse width and frequency match specifications.
- Another counter counts each screen line from 0 to 628, aligning with timing specs to validate the signal.
- VGA interface requires additional signals for red, green, and blue colors, synchronized with horizontal and vertical counters to track screen painting.
- Red, green, and blue signals determine pixel colors based on monitor position, with counters indicating the current pixel being painted.
- Pixel data for display is stored in a 28C256 EEPROM, with horizontal and vertical counters used as addresses to retrieve pixel color information.
- Due to a 10 MHz pixel clock, the resolution is 200 by 600 pixels, necessitating adjustments to the vertical counter for better proportions.
- To convert 8-bit data into VGA-compatible voltages, a voltage divider with specific resistors is used to achieve varying shades of red, green, and blue.
- By combining binary data using resistors, 64 different colors can be generated for display on the VGA monitor, with specific voltage levels for each color component.
11:29
"Creating 64 Colors with EEPROM Circuit"
- The circuit generates 64 colors by controlling the amounts of green, red, and blue using resistors.
- The resistors are connected to the outputs of an EEPROM, with 1.5 K resistors for red, green, and blue, and 680 Ohm resistors for blue, green, and red.
- The circuit is connected to a monitor using a 15-pin VGA connector, with red, green, and blue connected to pins 1, 2, and 3 respectively.
- An issue arises where the EEPROM outputs white during blanking intervals, potentially damaging the monitor.
- A NAND gate is added to control the output enable signal of the EEPROM during blanking intervals.
- An image is resized to 100 by 75 pixels and converted to indexed color mode with a custom palette of 64 colors.
- The image data is converted into pixel bytes using a Python script and written to a binary file for the EEPROM.
- Due to the EEPROM's access time delay, black vertical lines appear in the displayed image due to invalid pixel outputs.
- The EEPROM's slow speed compared to the monitor's expected pixel rate causes discrepancies in pixel output.
- In a computer, images are stored in SDRAM for fast access and immediate image changes, unlike the EEPROM-based system requiring reprogramming for image updates.
23:45
Accelerated video editing process with slow output.
- The video editing process can be accelerated, although the video itself may appear slow; the primary objective was to display an image successfully. To replicate this, visit the creator's website for schematics, data sheets, and parts. The production of such videos is time-intensive, made feasible by the support of patrons who enable the creator to continue making content.
