Garbled or no text on LCD; some flickering in output signal

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  • May 15, 2021 at 1:41 AM #47357
    Roke
    Participant

      I am having a hard time troubleshooting my DIY OSSC. I’ve put together a few in the past without problems, but I’m doing another one now as a gift and can’t figure out what’s going on. The issue is that the OSSC usually starts up with a blank screen, but can occasionally display garbled text. It also displays a test pattern and has no problem outputting a signal when I tested with my N64, but there is some flickering on the image that isn’t present on my own personal OSSC. The FPGA programming succeeds without any errors.

      I’ve attached some images below and a clip of the flickering here. To make sure it wasn’t the FPGA I replaced it with another one I had, but I’m getting the same problem.

      I’ve checked with a microscope for any solder bridges etc., and couldn’t find any. I’ve also reflowed solder on all the components. Anyone have an idea of which components could be at fault here?

      Thanks!

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      October 11, 2021 at 7:56 PM #49707
      marqs
      Participant

        The issues shown on character display indicate there is an issue either with I2C or LCD RS/CSn pin connections. Another possibility is 3.3V rail – have you measured its voltage?

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