Search found 44 matches

by amushrow
Mon May 01, 2017 2:50 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

So forgive my ignorance but how exactly do the diodes and resistors achieve the level-conversion? The diodes will drop the voltage in a similar manner to having just a resistor, the key difference being that a diode will need a minimum amount of voltage before current will flow through it. The idea...
by amushrow
Mon May 01, 2017 12:55 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

I don't want to have to route another board ever again, at least not one with so many vias in it. top.png bottom.png Now all I need to do is make it, and as I've managed to brew a sufficiently potent activator solution for plating the through holes, the rest should be easy. (Except for the drilling,...
by amushrow
Sat Apr 22, 2017 10:54 am
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

I'm going to make a board with diodes instead of the transceiver like I said, and see if it works out. If the board turns out well I'll stick up a guide on making PCB's at home; with plated vias, solder mask, tinned traces / pads, and a durable coating for the cart pins. Unless it doesn't turn out t...
by amushrow
Tue Apr 18, 2017 10:33 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

So, we can use diodes to reduce the voltage to the buffer, and in my test on a breadboard it seemed like it would work fine. But it doesn't, as I suspected the current is so low it leaks through anyway. With a 2.7v Zener diode the 5v from the Mega Drive is dropped to 3.5v (a ways off 2.7v). The 1.5v...
by amushrow
Mon Apr 17, 2017 12:41 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

I can't trigger on the event specifically, but by upping the persistence on the scope (so traces stay on screen for longer) I've seen it on a regular cart. This ain't my thing either really, I'm just learning things as I go here. I can string together some resistors and see how the MD behaves with a...
by amushrow
Mon Apr 17, 2017 10:53 am
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

Yes, it does still crash. I'll look a little more in depth to see if it's still doing exactly the same thing We'd have to drop the voltage coming in to the bridge board for the address lines, it may be possible to just use a diode but there's very little current flowing (basically none, less than a ...
by amushrow
Mon Apr 17, 2017 12:00 am
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

OK, try this new FPGA binary . It stops driving the data bus soon after /OE deasserts, and it refuses to return the state-machine to the idle state until /OE has been deasserted for four consecutive cycles. Still no better. I feel the issue is with those address lines sitting at 1.5v, a whole bunch...
by amushrow
Thu Apr 13, 2017 11:13 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

Not had much time to check anything today, but: Pull Up on CAS0 - no effect Pull Down on an address line - At the point of our error you can see that when it reaches 5v it slowly falls off instead of holding there, but the 1.5v period still remains. So something is keeping it there. Also, if there i...
by amushrow
Wed Apr 12, 2017 10:27 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

How consistent is the time between the /OE assert and the rising-edge of the first spurious spike? From a sample size of about 10, the address lines always rise up (or drop off) at the same time at the unwanted deassert of of CAS0, and they pick a very unfortunate level to sit at which tickles the ...
by amushrow
Wed Apr 12, 2017 9:29 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

I've finally found another sign of something going wrong apart from CAS0, some of the address lines are showing something. A few of them are switching to ~1.5v during the problem. I repeatedly saw A15 drop from 5v (to ~1.5v) and A08 & A11 rise up to ~1.5v A08 MegaDrive Side: A08_MD.png A08 FPGA Side...
by amushrow
Wed Apr 12, 2017 6:57 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

The noise is identical with the test FPGA gubbins. We still have the extra deassert that shouldn't be there, which doesn't look like noise (not to me anyway):
Bonus Deassert.png
Bonus Deassert.png (3.65 KiB) Viewed 2672 times
80ns/division
by amushrow
Tue Apr 11, 2017 11:51 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

I'll have to check any FPGA changes tomorrow, for now it's another dump of interesting information, which somebody somewhere may be able to make sense of. So, I've seen the noise on CAS0 but it's a very thin lonely slice of what's going on. So I've plugged in my super cheap logic analyser, and while...
by amushrow
Mon Apr 10, 2017 10:06 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

Yes, I'd seen those posts, which is what prompted me to poke in that spot (and also read up on more than I actually wanted to know about the Mega Drive) You could add logic to cover up the issue, but it doesn't fix the real problem (and I become less sure of the problem the more I look at it), I've ...
by amushrow
Sun Apr 09, 2017 3:04 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

5v rail is completely stable, as is the 3.3v on the UMDK. Just to eliminate another possibility I also checked a little closer and the MD is triggering the UMDK, which was already assumed I assume. This just means that there isn't noise on the 3.3v side of the bridge board which is getting sent back...
by amushrow
Sun Apr 09, 2017 12:04 pm
Forum: UMDK
Topic: MD hangs after playing any PCM file
Replies: 69
Views: 14109

Re: MD hangs after playing any PCM file

I already checked with a regular cart and there was no noise. I don't have any other flash cart, if you wanted a comparison for that. MDII has no problems at all (well, I haven't encountered any). They're both using the same power supply, actually a bench power supply. My Mega Drives 10v brick was p...