Tektronix TDS744 CRT to LCD color converter FPGA module DIY

[TerrySt]

My TDS-524A RAMDAC uses 640 x 480 resolution.  I believe the VGA output on the back is also 640x480.
This actually made it difficult to find a display, since most have moved to 800x600.
But the one I found is 640x480 so no conversion was required.  The only change I had to make was to the clocking to the LCD, which was a serial (LVDS) instead of the older parallel TTL interface.

Terry

[Tantratron]

Thank you Terry for your return of practice regarding the 640x480 at RAMDAC level.

What is strange with my TDS784D, when connecting its VGA port to a multi-resolution LCD driver with RTD2660 scaler chip standard board (PCB800099-V9), part of my TDS image is lost (see attachements) when I choose 640x480 resolution. I only have 640x480 display to try (either TTL or LVDS) but the RTD2660 chip declares 800x480 for some reason (see again attachments).
Of course, the internal TDS board chip in charge to translate or transcode the RMADAC signals into VGA could be the culprit, no idea.

See below camera picture of my TDS784D with SimConn Labs kit then its VGA output result feeding the RTD2660 chinese driver.

P.S. One reason this caught my attention is that a TDS754A on eBay told me to have installed a 800x600 LCD-display and driver connected to J88 (VGA link).

Albert

[TerrySt]

I don’t know what would be causing the display to lose pixels on the ends like that.  Post 33 shows what I got with my scope. 

Terry

[Tantratron]

Ok Terry, now I verify what you said earlier with your TDS524A. Indeed wether at RAMDAC level or VGA output, same 640x480 resolution with my TDS784D where an external DELL display indicates input to be 640x480. So this means the LCD table allocation of the RTD2660 cheap chinese LCD driver has either a firmware bug or the Sync, the Porches values chosen by tektronix back then in 90's are not so standard fooling the rescaler.

[Tantratron]

Thanks to Terry in this thread and another one, so the native pixel resolution 640x480 at RAMDAC level is indeed 25 MHz. I wanted to push the exercice to compare FPGA approach versus VGA on image quality but for some reason most LCD driver from AliExpress or eBay cannot self-adjust to TDS500/700 resolution neither auto-position the TDSxxx video format. However with an arduino DUE hack (proof of concept) controlling the scaler video chip RTD2660H from this 10 € driver board, it is doable as shown in my quick video this morning.



I'm still interested to go after FPGA wether TDSxxx or another project with Advantest which is more complex because again the RGBs format is not conventional plus frames are interlaced. However it is still an open question which FPGA chip and designing tool to choose, some mention Gowin Tang Nano. Would you have some return of experience or suggestions ?