Well, it's christmas today, so I hope you're all enjoying a calm and
peaceful evening with your family or beloved ones!
And those who aren't: Well, don't let that bring yourself down.
You're part of our community at least, you got friends here :)
Anyways, christmas is also a day you give and receive presents - and
while I can't give you your Pyra yet, I've got some quick news for you!
And no, it doesn't have anything to do with case colors... but some
very important color changes in simulation.
Soo... your personal christmas present is:
The redesigned CPU board passes all simulated tests!
Nikolaus found the time to finish his improvements on the CPU board
early this week and Juliano already found the time to run the
simulations - thanks a lot to both of them!
And thanks to Juliano who made a nice video, you can get another view
behind the scenes and see the improvements here:
https://www.openpandora.org/downloads/Pyra_DCIR_20171221.mp4
Just a quick reminder what the issue was and what happened lately:
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The current prototypes we are using did fail horribly with the DDR
connections... huge voltage losses, which are most probably the reason
they only work with 2GB.
The first improvements made by Nikolaus end of November did fix all the
DDR traces so they fully pass and don't have any voltage losses, but
the power supply still had some areas left which didn't pass the test.
This doesn't necessarily mean that this is a problem - it just means
that TI doesn't guarantee all OMAPs will run without issues if they're
not being used within the specs.
And while we didn't have any power supply issues with the OMAP with our
currently used CPU boards, it could still be they will cause issues
under some circumstances (for example, when the 3D Chip is heavily used
together with NEON code and a high clock rate, etc).
So we wanted to see if we can fix those as well.
A few weeks after the DDR fixes, Nikolaus tried to optimize these areas
as well - with great results.
All of the tests pass - it's highly unlikely the CPU boards will have
any issues now!
Yes, now the mainboards AND the CPU boards should be done.
Another puzzle fully finished, it seems!
Time to order prototype PCBs!
What have we learned from all of this?
Simulate, simulate, simulate.
Seriously, while this wasn't necessary at all with older SoCs like the
OMAP3, it seems impossible now to get a properly working design with
modern SoCs without simulating it.
This knowledge will greatly help with future CPU board upgrades (but
let's finish the OMAP5 one first :))
For anyone interested, here is the comparison table with the most
important power supply stuff of the OMAP5 of the version before and
after the fixes:
https://www.openpandora.org/downloads/Comparison_200mA.png
As usual, feel free to ask questions and discuss at the boards here:
https://pyra-handheld.com/boards/threads/important-color-changes.82241/
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Greetings,
Michael Mrozek
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OpenPandora GmbH
CEO: Michael Mrozek
Schäffbräustr. 11
85049 Ingolstadt
Germany
Tel.: +49 841 990 5548
http://www.openpandora.de/
HRB 4879, Amtsgericht Ingolstadt
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eMail: mrozek(a)openpandora.org
