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MEGA65 HDMI Output Flickers

  • I tried with another power adapter (the U64 one, has exactly the same plug, 12V an 2A).

    The machine ran stable for about 7 minutes, after that, going on with resetting intermittently after 10-200 seconds.

    There was a problem with reset glitching, which we believed to have universally fixed. However, it looks like yours is very unlucky.

    There are some improvements to this in the latest core, which we should find a way to get on your machine for you.

    The problem is a temperature related one (I can go into the details if you like, but not required just now. It's not a hardware failure, but rather a logic edge case when the main and MAX10 FPGAs clocks drift too far apart). This is also likely why it was stable for several minutes on first turn on, as the MAX10 FPGA would have been cooler than after running for a while.

    So, assuming you don't have a TE0790 JTAG adapter handy, turn the machine off, and have it somewhere cool (but not in the fridge, or somewhere like that, which would result in condensation), and you should get longer on first run, hopefully, long enough for you to do the core update, which should be more stable. Alternatively, a can of freeze spray and giving a quick squirt to the MAX10 should be broadly equivalent.

    If the problem persists, we can look at further solutions. One way or another, we will get you up and running stably. Email me direct at paul@m-e-g-a.org if you wish, as I am not keeping up with all the traffic here at the moment.


  • Hej, I am facing the exact same problems as described in this thread. These are,

    a) over HDMI I have a flickering/disappearing screen

    b) random and frequent resets

    The machine is as delivered, i.e., I did not modify anything yet, no battery, no extra SD card, and nothing else yet. Initially, I thought the spontaneous and cycling resets might be a contact problem with the internal SD card. Thus, I removed it and inserted it again, but the problems remain. Unfortunately, I do not have another suitable power supply as EzellaGarnie and cannot check if it would change anything.

    What shall I do, shall I also write you Paul an email directly, shall I contact Trenz, or what is recommended?

  • Hi, Paul Gardners reached out to me. He immediately had an idea. As far as I understood him, it is a problem that leads to heating of the Max10 FPGA (the smaller one on the board). The power supply is not the cause.

    As long as that chip is sufficiently cooled, my Mega does not reset anymore.
    He is trying to write a fix into a bitstream which should be available in the next few days. Until now I am not sure if the HDMI flickering is related to this or not. My tests indicate that at least one monitor gives a much more stable HDMI output when that chip is cooled...
    PM me so we can keep each other informed....

    Great community, You get help immediately!

  • Hej @EzellaGarnie, thank you for the update!

    I am new here, tried to find how to send you a PM, but I cannot find anything like that in the menus...

    Therefore, I ask here: How do you cool that chip? I do not have any freeze spray as Paul suggested above. and was just thinking a heatsink could do? Is that enough in your case, or do you use something different?

  • Since I do not have a heat sink at hand, I tried with a cooled piece of ceramics on the chip. That allowed me to at least format an SD-card in slot 1 without a reset. But already after some minutes, when the piece of ceramics reached room temperature again, the resets and cycles of resets started again.

    While cooling the chip, I did not perceive any positive change with regards to the flickering over HDMI. The only way I can reliable see an image is via VGA.

    I do not know if it is related or not, but when running the vector clock from the demo, I can see that it is not "ticking" as a clock is supposed to, i.e., one tick per second. Instead, the clock leaps over and jumps back and forth between time values.