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I’ve just joined to this forum, and first I would like to congratulate to you all for this wonderful project. I’m about to build OS and the AC board myself.
The first issue I found is a strange problem in the Eagle board files. Pads of some connectors are misaligned. In the footprint designer it is OK, but on the board not. I attach some pictures. As I cannot find the original eagle lbr files, I just replaced them with similar types. I’m using the latest Eagle software.I realized that I can export the libraries from the sch files. Checking them I see that the TX connector and the display connector is intentionally like that, the pins are not in one line. (So far I have seen SSD1206 with straight pin arrangement only.) The connector M04x02 pins will return to the normal position after updating the connector from the library.
An other observations: On the extender board there are DGND and GND lines, which are not interconnected in the schematics. I think they should be, as on the board they are interconnected. It confused the Eagle, so C2 has no GND connection (just hanging in the air) without airwire or warning. The GND line from RS to the GND pin should be thick conductor, as current of all loads (including the extension boards) are going through here.The misaligned pins are intentional — they are called ‘locked’ pins. Their purpose is to create slight mechanical tension so that the through-hole parts will stay in place even without soldering. The LCD in particular is not soldered, so this locked pins are important to make sure the pins and pads have good physical contact.
The GND and DGND was a mistake in an early version of the AC driver design. It has since then been fixed and I may have forgotten to update the files on Github. The mistake made one leg of C2 (decoupling capacitor) hanging and not connected, but it doesn’t affect the functionality of the board.
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