Learning to use a logic sniffer

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sweh
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Learning to use a logic sniffer

Post by sweh » Fri Apr 10, 2015 12:26 am

So a year or so back you guys helped me to learn how to use a scope. I think I know what I'm doing, there... Well, perhaps a little!

Now I have a Open Bench Logic Sniffer with 2 sets of cables.

Does anyone have any recommendations on how I should start to learn how to use this thing? That way I can hook it up to my broken Master and maybe see some interesting things... maybe :-)
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roland
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Re: Learning to use a logic sniffer

Post by roland » Fri Apr 10, 2015 3:40 pm

For the best results you better add a wing to expand your OLS to 32 channels. Then you can monitor the address bus, databus and control bus simultaneously.

For now, with 16 channels you can use 8 channels for the lower address lines and use the other channels for e.g. R/W, Phi2 and reset. You can use the reset line as a trigger, so the capturing of data starts when reset goes from low to high. The processor starts with fetching the reset-address at &FFFE/&FFFF so on the address bus you should see $FE and then $FF. Use a sample frequency of at least 10MHz. In these samples you will probably notice some transient states but with a little practise you can discover the pattern. Connect unused channels to either GND or +5V. I have seen strange results when one or more lines are floating.

Also very useful is a dis-assemly list of the rom you are analysing, so you know what you should see.

AFAIK there is no protocol analyser that reads the captured data and shows is like an assembler listing.
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Re: Learning to use a logic sniffer

Post by sweh » Fri Apr 10, 2015 5:37 pm

roland wrote:For the best results you better add a wing to expand your OLS to 32 channels. Then you can monitor the address bus, databus and control bus simultaneously.
Aren't the other 16 channels limited to 3.3V? I'd be worried about connecting them to TTL devices... ( http://dangerousprototypes.com/docs/Log ... ing_scheme )
You can use the reset line as a trigger, so the capturing of data starts when reset goes from low to high. The processor starts with fetching the reset-address at &FFFE/&FFFF so on the address bus you should see $FE and then $FF. Use a sample frequency of at least 10MHz.
Thanks, that makes sense :-) (if I'm just using reset as a trigger I could probably use 15 bits of address space)
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Re: Learning to use a logic sniffer

Post by hoglet » Fri Apr 10, 2015 5:57 pm

sweh wrote: Aren't the other 16 channels limited to 3.3V? I'd be worried about connecting them to TTL devices... ( http://dangerousprototypes.com/docs/Log ... ing_scheme )
You need to use one of these:
http://www.seeedstudio.com/depot/Logic- ... p-721.html

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roland
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Re: Learning to use a logic sniffer

Post by roland » Fri Apr 10, 2015 10:30 pm

That's correct, with that wing you add 5V tolerant buffers to the remaining 3.3V inputs. It's really worth the money and it works like a charm :)
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Re: Learning to use a logic sniffer

Post by sweh » Fri Apr 10, 2015 10:46 pm

OK, one of those ordered along with 2 more cable sets :-)
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Re: Learning to use a logic sniffer

Post by DutchAcorn » Mon Aug 08, 2016 8:38 pm

So I also ordered and received the buffered wing with my logic sniffer. I am not sure about the best way of attaching the wing to the main PCB though, has anyone else done this?
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Re: Learning to use a logic sniffer

Post by roland » Mon Aug 08, 2016 9:51 pm

Yes I did. I'll post a few pictures tomorrow.
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Re: Learning to use a logic sniffer

Post by roland » Tue Aug 09, 2016 6:04 pm

This is how I did it:
image.jpg
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Re: Learning to use a logic sniffer

Post by DutchAcorn » Tue Aug 09, 2016 7:03 pm

roland wrote:This is how I did it:

image.jpg
Thanks Roland! I guess that's a logical way: fix sockets and headers :D
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Re: Learning to use a logic sniffer

Post by sweh » Tue Aug 09, 2016 11:27 pm

FWIW, I just used a pin connector and soldered both sides
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Re: Learning to use a logic sniffer

Post by hoglet » Sat Oct 14, 2017 2:19 pm

roland wrote: AFAIK there is no protocol analyser that reads the captured data and shows is like an assembler listing.
There is now.... :D

See this thread:
http://www.stardot.org.uk/forums/viewto ... 42#p182742
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roland
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Re: Learning to use a logic sniffer

Post by roland » Sat Oct 14, 2017 9:51 pm

That is really great =D> I will try it when I have my man cave finished 8)
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