After a long time, I've decided to make a board for this, based on the R2R DAC from http://belogic.com/uzebox/schematics/uz ... mal_v2.pdf. I just sent the board the JLCPCB.
Here is a picture of my board from a Gerber viewer from JLCPCB. There is no AD725 chip, course. The board has:
1) USB power only, no DC connector, thus no 7805 regulator, because one can get a USB plug to have 5V of 1A minimum output.
2) I put in the CH340G, a very usable AND cheap USB-serial chip.
3) SD CARD has multiple connection support, include the original, micro-SD card, or simply headers.
I don't know if it works, but I will try it out when the board arrives.
Attached is the image.
Grayscale Uzebox (no AD725)
-
- Posts: 36
- Joined: Sat Sep 19, 2009 7:46 am
Grayscale Uzebox (no AD725)
- Attachments
-
- UZEBOX-GRAYSCALE.png (205.26 KiB) Viewed 7985 times
Re: Grayscale Uzebox (no AD725)
This one should be interesting to see and I am curious what the grayscale looks like for games. So do you think the CH340G can be used for flashing, or did you envision some other PC<>Uzebox communications?
-
- Posts: 36
- Joined: Sat Sep 19, 2009 7:46 am
Re: Grayscale Uzebox (no AD725)
Yes, the USB serial is there for flashing and communication. I figured if I have USB as the power, might as well throw in the CH430, which is dirt cheap compared to FTL232 USB-serial chip, and the CH430 works well.
Re: Grayscale Uzebox (no AD725)
By the way, if you want a proper RGB->grayscale conversion, you might want to use the resistor network from the "Y" channel of the Y/Pb/Pr design I posted here. This network should also be more correct WRT the 75 ohm termination (the original black&white uzebox design uses 75 Ohm to ground in parallel with all the other DAC resistors, resulting in less than 75 ohm effective termination resistance).
- Y - GND: 120
- RED2 - Y 2k3
- RED1 - Y: 4k3
- RED0 - Y: 8k2
- GREEN2 - Y: 604
- GREEN1 - Y: 1k2
- GREEN0 - Y: 2k4
- BLUE1 - Y : 6k2
- BLUE0 - Y : 13k
- SYNC - Y : 604
- Attachments
-
- uzebox-y.png (717.46 KiB) Viewed 7377 times
Re: Grayscale Uzebox (no AD725)
Hey nice work, it looks good
Re: Grayscale Uzebox (no AD725)
Nice work! Have completed the whole build and it's working? If so can you send me your gerbers, schematic and BOM so I can add them to the downloads page of the website?
Re: Grayscale Uzebox (no AD725)
Today I tried to connect my small 4.3" TFT to the Uzebox. As RGB converter I have the MC1377 from Motorola clamped in between. Actually works but the colors are not so nice and there is a lot of interference when touching the capacitors.
Unfortunately I don't have an AD725 and it is also very expensive. Ok, in China you can get them for under 5 dollars.
But what works is a stable and high contrast grayscale image.
Now I'm thinking about building a portable Uzebox and getting an AD725 from China in parallel.
Unfortunately I don't have an AD725 and it is also very expensive. Ok, in China you can get them for under 5 dollars.
But what works is a stable and high contrast grayscale image.
Now I'm thinking about building a portable Uzebox and getting an AD725 from China in parallel.
The last digit of Pi is 7! I calculated this, as I counted to infinity yesterday!