Logic Shrimp as a pattern generator

The Logic Pirate is a medium speed, low-cost logic analyzer with a USB interface. It can capture up to 256K samples at 20MHz (80MHz with overclock), and is compatible with SUMP logic analyzer client. Get one for $30 at Seeed Studio. Logic Shrimp support available here.

Logic Shrimp as a pattern generator

Postby bhunting » Fri Apr 08, 2011 7:12 am

I just ordered a logic shrimp from seeed studios. I'm not in dire need of a logic analyzer given that I already have a Saleae and an OLS, but I am interested in a 20MHz pattern generator.

It looks like it would be straightforward to reconfigure the logic shrimp as a pattern generator, the hardware seems all in place.

The question of course is the software. Is anyone working on a pattern generator firmware or client for the logic shrimp?

Would it be best to integrate a pattern generator into the logic analyzer firmware and Jawi's Logic Sniffer client or make a stand alone firmware and client?

It also seems there would a glitch in the pattern each time the pattern reset if the patten length was not exactly 256k long.
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Re: Logic Shrimp as a pattern generator

Postby ian » Fri Apr 08, 2011 8:17 am

I'm really excited about this aspect of the project.

It would be nice to unify something into the client, that way stored logic captures can be easily played back. Also, it should be possible to do something similar with FPGA hardware so it might be handy for other projects too.

I'm not a java programmer though, so I plan to make some small C apps that feed data for testing. THat'll get me through the firmware development. Once support is there, maybe someone would be interested in exploiting it.

There is also a 32 byte page read/write mode with wrap around. You still need to be exactly 256 ticks, but it is easier than programming and dealing with the full 256K.

Any thoughts or requests?
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Re: Logic Shrimp as a pattern generator

Postby ian » Fri Apr 08, 2011 8:19 am

Would it be best to integrate a pattern generator into the logic analyzer firmware


That is my plan, I'll add extensions to the SUMP protocol for upload and replay.
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Re: Logic Shrimp as a pattern generator

Postby bhunting » Fri Apr 08, 2011 9:14 am

I can work the Java side. I assume we are talking about using Jawi's OLS client? I've downloaded the source and poked around a bit. I have not built it but that could be a project for this weekend.

I could also kick off a standalone java client to get something up and running until it can be integrated into an existing client.

The shrimp page says you are using a subset of the SUMP protocol to get the data capture out. Are you thinking to use the SUMP data transfer in reverse to get the pattern down to the shrimp or are you thinking a whole new transfer protocol?
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Re: Logic Shrimp as a pattern generator

Postby ian » Fri Apr 08, 2011 9:20 am

I thought we could just add some well-chosen new 4-byte SUMP commands (we extended it like crazy for the Open Logic Sniffer) for load (including the number of bytes to expect) and playback (including memory range to replay?). Speed would be set by the normal SUMP dividers. We can keep things in flux until the bugs are worked out :)

Working in the existing client, or a new stand-alone test bench that would be integrated later are both fine options.
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Re: Logic Shrimp as a pattern generator

Postby jawi » Sat Apr 09, 2011 12:13 pm

Superb idea, bhunting!

For what its worth: I've significantly simplified the way new menu's can be added to my client in 0.9.4-RC2, so it would be easy to extend the client with new functionality.

I'm intending to write a short howto on this, which might simplify or remove the need to write a separate client for this feature...
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Re: Logic Shrimp as a pattern generator

Postby ohhteriiii » Sat Jan 24, 2015 7:47 am

It would be nice to unify something into the client, that way stored logic captures can be easily played back. Also, it should be possible to do something similar with FPGA hardware so it might be handy for other projects too. I'm not a java programmer though, so I plan to make some small C apps that feed data for testing. THat'll get me through th??
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