And again a new Gigatron fan

[brian]

Hi Hans,

I have been looking at your Gigatron PCB views in your post dated 28 Feb , one is blue and the other is yellow.

Looking at the expansion patchwork you appear to have wired pins 13 and14 of the 74HCT273 differently.

On the blue version the red wire from pin 14 appears to go to J2 pin 4 and the blue wire from pin 13 goes to J2 pin 3.

However on the yellow PCB this appears to be reversed. Here the blue wire clearly goes to J2 pin 3.

Which is correct, the blue PCB view or the yellow PCB view?

After reading the various posts concerning this topic by others I believe the yellow version is correct but now seek some clarification as to which version is actually correct.

I now live in France but my native language is actually English with some French but not much German.

Your kind response would be appreciated

Brian

[Hans61]

Hi Brian,
thank you very much for pointing it out. I hadn't noticed it yet. After the design change here:
https://forum.gigatron.io/viewtopic.php ... 4&start=50
I wired the blue wrong. Thereby A6 and A7 are swapped, the signals B0 and B1 are responsible for the RAM above the 32kByte memory.
In practice both should work, because the Gigatron doesn't care which physical RAM is mapped into the upper 32k, as long as it is always the same.
But it was not intentional but my mistake. But I will correct it on principle. At the moment I still have problems with the startup of the SD card at the SPI of the Gigatron.
I haven't had time to investigate the problem yet. When I have solved the problem I will definitely make a corrected PCB, if there is none yet. That should be the better solution.

[Hans61]

As a soldering exercise for a new project, I built two extension compacts from lb3361 (https://github.com/lb3361/gigatron-lb). A nice little board.

expansion-compact-top-web.jpg (45.09 KiB) Viewed 11305 times

expansion-compact-buttom-web.jpg (40.39 KiB) Viewed 11305 times

gigatron-yellow-with-expansion-compact-web.jpg (238.5 KiB) Viewed 11305 times

sd-card-holder-web.jpg (33.28 KiB) Viewed 11305 times

To get a little more mechanical hold for the SD Breakout, I made a simple bracket with FreeCAD. I printed it on the 3D printer. You can find the files here: https://github.com/hans61/FreeCAD.

[Hans61]

A few more pictures of the extension-retro v7 from lb3361.

gigatron-with-extension-retro-v7-web.jpg (158.94 KiB) Viewed 11305 times

extension-retro-v7-web.jpg (178.36 KiB) Viewed 11305 times

The board and SD card browser of lb3361 support two SD cards. In addition, two additional 8-bit output registers can be connected to the expansion port (74LS377, 74LS273, TLC7524, ...).

[Hans61]

The current version of the "Multipuruose Expansion Board" from lb3361. This should be the end of the hardware development. I have a (bad) video of the possibilities here: https://www.youtube.com/watch?v=NkXx2jeCFOU

gigatron-multipurpose-expansion-board.JPG (126.43 KiB) Viewed 10972 times

If there is a need, I can build extensions (material costs plus shipping). I ship from Germany (the most expensive is DHL worldwide €12.89 in the EU much cheaper). Currently I would sell a board for 45€. If necessary, I would order material in a timely manner. Two boards would currently still be available.

gigatron-with-expansion-board.JPG (116.88 KiB) Viewed 10972 times

gigatron-multipurpose-expansion-board-bottom.JPG (162.16 KiB) Viewed 10972 times

gigatron-multipurpose-expansion-board-a15.JPG (85.68 KiB) Viewed 10972 times

gigatron-boot-512K.JPG (169.35 KiB) Viewed 10972 times

[Hans61]

A solder bridge can be seen on the underside of the expansion (JTAG between TDI and TMS). This is a mistake. I had removed them before the test. The picture is an accident.