Oh brother, this is starting to get complicated.

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The RA8875 is a 3.3V chip… and the inputs, as far as I can tell… from my research so far… are only 3.3V tolerant.??

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To make this more confusing, some of the display.com displays have level shifting hardware onboard that you can enable to use the display as a 3.3V display or as a 5V display (in line with the power selections on the MAIN board).? However, not all do (particularly the smaller displays). ?The boards I made work with 3.3V and 5V display boards… which is fine for 3.3V operation for all display boards…. The problem comes if you select 5V operation bon the MAIN board… but either don’t have a 5V control line selection on the display board for level change to 3.3V for the RA8875… or if you DO have the level change hardware on your display board but have not selected it.? In this case, you will destroy the RA8875 chip.

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I can do two things.? One is to put together a list of all the approved Display.com display part numbers (upper middle of the back of the display) and give guidance on what you need to do so that the display continues to function with this driver board.? The other thing I can do is make a second board that has a tiny 3.3V regulator on it to power the three control lines to just 3.3V in the case of running the display off 5V but no hardware is there for level shifting the data lines to 3.3V.

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Comments? ??????

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Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

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Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

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Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

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Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

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email:? bill@...

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