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Topic: Saleae Logic Analyzer Output (Read 2113 times) previous topic - next topic

HugoPT

Hello all
Not sure if this is the right place to ask for my question but where it is:
I have a logic Analyzer Saleae Logic 8 and today I had need to "Watch" the RB port in a PIC device.I attached the leads and capture the data I want.
Now when I go to analyze the data I see the data is there but  can´t see where a byte starts and ends.I can just measure the timings in fact.I don't know what kind of signal is passing there( I2C, UART, SPI ...) so I can´t analyze that properly.I was looking in the Saleae Manual but I can´t find nothing that could help me showing my unknown data in a read format.I need to see how many bytes I had received and what values they are, but I can just see the signal in a time base.Moving the cursor above the signal doesn't help to much.
I attached below a print from my data.
How can I use Saleae Logic analyzer in an unknown signal?



Can someone help me
Debian,Mint,Ubuntu
Arduino Mega 2560
Arduino Nano
Arduino Duemilanove
MAC OS Montain Lion
Raspberry PI Model B

Nick Gammon

For a start, it looks balanced (notice how the second channel is always the inverse of the first).

So you can probably concentrate on one channel only. My initial guess would be to take RB1 and see if applying the "Async Serial" analyzer gives anything useful. Try setting it to "autobaud" and have it guess the baud rate. I'm suggestion RB1 because serial is "normally high" and goes low at the start of the byte, which is what RB1 is doing.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

HugoPT

Thanks Nick for your great fast answer
Quote
For a start, it looks balanced (notice how the second channel is always the inverse of the first).

I notice that, it look like a RS485 Signal but it's not.One is the opposite from the other just.
The PIC is in a RFID circuit, the pic read the coil when the card is passed above it and the this data appears in RB0 and RB1 only.
Apart of this if I don´t know what signal I'm dealing with saleae is useless right?
It just can deal with signals that are implemented in the Analyzers right?
Debian,Mint,Ubuntu
Arduino Mega 2560
Arduino Nano
Arduino Duemilanove
MAC OS Montain Lion
Raspberry PI Model B

afremont

Looks like some kind of Manchester encoded data.  Until you said something about RFID, I was going to guess some kind of IR protocol.  A quick search in Google for Manchester and RFID turns up a number of interesting looking hits.  EM4100 sound familiar?
Experience, it's what you get when you were expecting something else.

HugoPT

Quote
My initial guess would be to take RB1 and see if applying the "Async Serial" analyzer gives anything useful. Try setting it to "autobaud" and have it guess the baud rate. I'm suggestion RB1 because serial is "normally high" and goes low at the start of the byte, which is what RB1 is doing.

Bingo you are rigth  :smiley-mr-green:
It is a Async Serial signal.
I can see the bytes know.For know I'm saved thanks to you but I'm still wondering if the Saleae team shouldn't have included some kind of General Logic Discover to try to find the Right protocol we are trying to listen.
 
Debian,Mint,Ubuntu
Arduino Mega 2560
Arduino Nano
Arduino Duemilanove
MAC OS Montain Lion
Raspberry PI Model B

Nick Gammon

Well, what's a RB port anyway? That should give a clue.

And no I don't agree it is useless. The analyzers are nice, but you also get to visually see the signals (as you have done) so straight away you know you are dealing with a balanced signal. BTW, USB is balanced too, so possibly it is USB.

You can see a whole lot of stuff there as well, such as the timings. Careful eyeballing, measuring (eg. with zooming) may indicate that some pulses are always twice the width of others, or not. So there are clues to be had there.

Some devices (like IR remotes) use variable PWM to convey information. I don't know that the Logic has every conceivable encoding system implemented just yet.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

Nick Gammon


It is a Async Serial signal.
 


Good guess, huh? Anyway you usually have some idea of what you are dealing with, and even if not, with experience you can usually pick patterns, as I did then. :)
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

HugoPT

Quote
Good guess, huh? Anyway you usually have some idea of what you are dealing with, and even if not, with experience you can usually pick patterns, as I did then. smiley

If you ever came to Portugal I would like to pay you a big beer  :smiley-mr-green:  :smiley-mr-green:
Debian,Mint,Ubuntu
Arduino Mega 2560
Arduino Nano
Arduino Duemilanove
MAC OS Montain Lion
Raspberry PI Model B

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