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Tektronix TDS744 CRT to LCD color converter FPGA module DIY

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TERRA Operative:
Great. If you find that you can compile code, I can draw up a PCB to test on.

Having another look at the datasheet, it seems I need to use the XO2-640U (not the XO2-256 that I can get off the shelf here) Lattice FPGA if I want dedicated LVDS output buffers and a PLL. Are these needed for this application?

ltarjanyi75:
Yes, that is what I have just found also, because I could not add PLL to the 256 type.
640U is the smallest with 1 PLL, which is required for 25MHz to 175MHz clock multiplication. The smallest package of this is 144 pin TQFP.
(Compared to Spartan 3, which has 100 pin package)

Otherwise I could modify the VHDL code to synthesize without the pin/IO constraints... I don't know yet know how this can be compiled to a programmable binary on this platform and also do not have cable/programmer etc. to test it.
But at least it still seems to be doable even if not with the smallest chip.

TERRA Operative:
Well, I can only get the non-PLL 256 type locally, so if I have to order chips, I may as well stick with the Spartan 3.

Do you have a link to the seller you bought from? If they are selling known good chips, I'll buy from them too.

(I just found Spartan XC3195A-3PQ208C for about 4000yen per 4 units being sold locally if they would work?)

ltarjanyi75:

--- Quote from: TERRA Operative on January 07, 2024, 01:37:44 pm ---Do you have a link to the seller you bought from? If they are selling known good chips, I'll buy from them too.

--- End quote ---
This is where I bought from:
https://www.aliexpress.com/store/1102598538/pages/all-items.html?sortType=bestmatch_sort&SearchText=XC3S50A

ltarjanyi75:
I had some time lately to further enhance my LCD solution. It was more a fun to build than it will be a frequently used feature. :)
The idea was to solve the brightness setting of the LCD (without opening the scope and changing DIP switch setting) which is possible by varying the duty cycle of the LCD PWM signal.

What I did:
- placed a resistive touch panel in front of LCD
- moved the PWM signal generation from FPGA to an atmega4809 chip/board (installed behind LCD) and program written with Arduino IDE
- Brightness can be set by (controlled by Atmega):
   - touching the upper right corner of screen for around 3 seconds
   - then you can set the value on the left of screen with the y value
   - you can save the value permanently by pressing save button (lower right)
   - if not saved the setting is only stored temporarily till the next restart
   - setting will disappear after not touching the screen for about 5 seconds
- FPGA code modified:
   - removed PWM signal generation
   - accept commands and brightness values from Atmega
   - necessary logic for brightness setting UI elements to overlay the pixel info received from scope during setting

The code could be further enhanced, but probably I will stop here. :)
(The resistive touch coordinate reading is not perfect, it has some false readings, but most of the time it works fine. And the UI is a bit ugly...)


https://1drv.ms/v/s!Am44vwFO-Vr3gsB13GQrtzPChORk2w?e=a98BJh

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