Problems getting color VDU working

[StormTrooper]

I've built a color VDU and double checked all the connections and soldering joints.
When I plug it all in I get either a red screen of G's or red G's with some random green characters.

This seems to suggest at least the video chip is working. I've tested all logic chips and also tested the 62256 ram chip - no issues there.

Have swapped out the MC1372 and MC6847 just in case, but made no difference.

Any ideas as to where to start troubleshooting on this?

The RC6502 is running fine and I can connect to the console via the Arduino and run basic programs.

[tebl]

The video chip doesn't initialize the memory in any way, so at startup you would usually get a semi-random result before you start writing values to it. Can't seem to remember a red screen though it is often just whichever value the chip happens to drift towards. Try setting the registers to a specific value, then just put some ASCII characters into the start of memory. søn. 13. feb. 2022, 16:16 skrev Greg McCarthy ***@***.***>:

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I've built a color VDU and double checked all the connections and soldering joints. When I plug it all in I get either a red screen of G's or red G's with some random green characters. This seems to suggest at least the video chip is working. I've tested all logic chips and alsl tested the 62256 ram chip - no issues there. [image: rsz_20220213_150304] <https://user-images.githubusercontent.com/1429043/153759760-cf49e927-9a0f-463d-888c-b7caf88f2584.jpg> [image: rsz_20220213_150334] <https://user-images.githubusercontent.com/1429043/153759785-6189da4a-204e-4603-a837-381144bd883b.jpg> Any ideas as to where to start troubleshooting on this? The RC6502 is running fine and I can connect to the console via the Arduino and run basic programs. — Reply to this email directly, view it on GitHub <#37>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGEF6ILSPPSSAKJ23NFIAQ3U27DLFANCNFSM5OJE4WFA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[0cjs]

In case it's not clear (because I think another another user may also have been unclear on this), the VDU board simply gives you a frame buffer in memory: you are responsible for writing the software that intialises it, prints text on the screen, and so on. Especially, the Apple 1 monitor (WOZMON) normally used with this system will not print anything on this display; the Apple 1 video system is very different from this, and does not even involve a frame buffer. (Apple 1 video is more like a terminal.)

The screenshots above look very much like what I would expect from a VDU board that's working but hasn't had any software initialise it.

[StormTrooper]

Thanks, very useful info linked above. I haven't had any time to further investigate this but that will be the cause then - no software has been done to initialize the VDU board.

Will close this issue as it's a lot clearer now.