sd2000 Posted November 6, 2006 Report Share Posted November 6, 2006 OK, this one has really got me pulling my hair out.Am just coming to the end of my 5th Core board, it’s going to be another MIDIO128, DIns are OK, LCD OK, problem is that the LEDs connected to the DOuts are always lit.By swapping with known working boards, I know that:The DOuts themselves are good, they work with 3 other boards.The PIC is good, it works with 3 other core boards.The LCD is good.The sequence of events is normally this, power up, the LEDs light (not flash), the LCD displays normal messages, yet the LEDs remain lit.Sometimes though, on power up the LEDs light, then go out, the MIOS copyright message is displayed and the Core locks up. It works fine with just DIns and fine when the DOuts are disconnected.The problem is somewhere on the core, yet all voltages seem OK, as do the solder joints and there are no obvious shorts anywhere. Have read the forum, tried the usual things (checked, double checked for shorts, solder blobs etc) but still no joy.Has anyone got any ideas at all? Because I am really stumped.Thanks in advance.SD Quote Link to comment Share on other sites More sharing options...
TK. Posted November 12, 2006 Report Share Posted November 12, 2006 Hi SD,it could be a power integrity issue, which happens, when too many modules (especially the ones which consume a lot of power like a DOUT fully stuffed with LEDs) are supplied from the core module.Bypass caps are a must here, did you add them to all modules? I would especially add a 100 uF cap between Vs/Vd of each DOUT module.I don't want to say that this is the problem, but there is a certain probability...Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
sd2000 Posted November 12, 2006 Author Report Share Posted November 12, 2006 Thanks Thorsten!Didn't have any caps at all on the DOuts, so stuffed the leads of a radial 100uF into the header of the first Dout, switched on and success!Even better when I called the Girlfriend in to press some keys (I can't reach the keyboard) and took the cap out, it all works perfectly!And it still does!Have no idea what that was as everything was working OK with the other boards, but it seems pushing the leads of the capacitor into the plug made something happen.Thanks again.SD Quote Link to comment Share on other sites More sharing options...
TK. Posted November 12, 2006 Report Share Posted November 12, 2006 Great! A nice example, that bypass caps can help when you have no other explanation for such strange effects :)Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
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