Very weird LCD problem...

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Joined: 31/12/2012
Location: New Zealand
Posts: 9171
Posted: 03:27am 08 May 2024      

  Glen0 said  Something to do with the power supply?

You win.  

I installed the wrong regulator!  

Supposed to be MCP1703A-33(3v3), I put in a MCP1703A-50(5v)

As soon as I spotted that, I had a bit of an "A-HA!" moment.
Replaced the 5v regulator with the correct 3v3 regulator, and everything sprung to life - on the original pin-out etc.

I took it from the static sheilded bag containing regs that SHOULD be 3v3, but I must have let one 5v slip into that bag, when I sorted them.  I will now check all regs in both the 3v3 bag, and the 5v bag, so as not to run into that again!

I guess I also should have been checking the part number on the reg itself, rather then just ASSUMING that every one in there, were the correct output voltage...

Again, a pretty schoolboy mistake, and I should have detected that WAY before now, and everyone also knows what assumptions are the mother of...      

That mistake, would have meant that the MM2 chip was firing 5v logic(or close enough to 5v) at the LCD, and I guess it upset the SPI port on the LCD module, whose I/O is 3v3 max I seem to recall.

I'm probably pretty lucky that I did not kill the LCD, but it still is working fine!  
Probably lucky that I did not kill the 170 MM2 chip too, as it is only rated for 3.6v maximum!

Edited 2024-05-08 13:30 by Grogster