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Question Shield Mojo to Alchitry
#1
Hello
I'm designing a circuit to make sure that the new Architry board shields can be mounted on Mojo V3.
Is it necessary that the wires from the mojo connectors to the new smd connectors have the same length?
From the photo of alchity Au the wires of equal length are the ones that go to the dram onboard but the ones that go to the connectors do not seem to me to be identical in length. Is that so?
In this last case it is not necessary that in the design of the pcb you implement the wires of equal length.

The attached file shows the board with 2 connectors with wires of identical length. But to make all 4 connectors the thing is quite complicated. It can be done but I have to waste some time.

I hope I have explained

Fabio
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#2
Generally speaking no. Most boards don't require this but it is helpful to keep them similar. The new Ft has traces of matched length but the differences on the Au are small enough not to matter much.

For a really high speed board, I would make the total trace lengths from Au to the element the same (using the Au length + element length to be the same) but I haven't had to do this yet.

If you wanted to ensure the maximum compatibility with everything then matching the length wouldn't hurt. It is unlikely to make a difference in most cases though.
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#3
Hi,
the fact is that if some experimenting user wants to build a fast board they might have trouble doing it due to the lack of track length information.

I would not be wrong but I have not seen the source project of Alchitry Au or cu, only schematic.

This problem arose when I designed a mojo shield that can accommodate alchitry expansion cards.

However, I agree that this problem could only occur in a limited number of projects.

Thanks
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#4
Here's a list of all the Au signal lengths is you really want to match them.
https://docs.google.com/spreadsheets/d/1...sp=sharing

In general, I don't have a problem sharing the Eagle files for the board if someone want's them for a reasonable purpose. I just haven't posted them like the Mojo because I found that the most common use for the Mojo ones was making crappy knock offs that eventually created complaints about boards we didn't even make not working.
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#5
(11-09-2020, 05:22 PM)alchitry Wrote: Here's a list of all the Au signal lengths is you really want to match them.
https://docs.google.com/spreadsheets/d/1...sp=sharing

In general, I don't have a problem sharing the Eagle files for the board if someone want's them for a reasonable purpose. I just haven't posted them like the Mojo because I found that the most common use for the Mojo ones was making crappy knock offs that eventually created complaints about boards we didn't even make not working.

Thanks,

As I have a little time I modify the adapter card.

Yes, I saw your cards have been copied, in fact I bought a fake mojo V3, but I must say that it works well. I also took some shields to experiment since originals are not found.

I don't understand the reason you retired the mojo V3, to start experimenting with fpga it's great I would say.
The connectors on the one hand are terrible but on the other hand they give easy access to the board.
For basic projects they are the best. Big Grin
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