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Author Topic: logic analyzer/sniffer for a novice?  (Read 3190 times)
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Hey guys,

have a few arduino projects under my belt right now and i've been tackling a relatively ambitious project.  I want to step it up a notch and have the arduino mega piggy back a cruise control system for my boat.   It wont be going against the arduino guidelines as i'll just be using the arduino to simulate button presses.  The thing that i need to figure out is how to know what speed the controller is set at so that i can display that information on my arduino's screen.   

the module has an lcd gauge (thats not mine but its similar):
http://img853.imageshack.us/img853/155/imagerwi.jpg

it looks to have a 10 wire harness.   

i took it apart and noticed that the 4 buttons on the front panel had a handy 5 pin header and socket.  (4 buttons, 1 common ground) 
http://onfinite.com/libraries/1663907/87b.jpg

i also found this device online that lets you control the speed wireless while being towed:
http://www.nautiqueparts.com/wirelessremoteforcruisecontrol.aspx  (speed up/ slow down)



this leads me to believe that the button presses are not serial and and the connect directly to digital inputs on the master module.   that would leave 6 wires on that harness for the display.   two of which are power and ground.  that would lead me to believe that it's a serial lcd?
 (edit:  i contacted the person who made that and the buttons do extend out from that wire harness.)

now to my question... does my logic sound correct?  and if so.   being new to coding and micro controllers.  would sniffing out the speed settings that are being sent to the lcd screen be within a novice's grasp?  and do you guys recommend any online tutorials/videos (or if you'd like to post directions here... id love that too)  that would show me the correct ways of accomplishing this task?



thanks in advance

scott
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i'm assuming this is harder then i suspect?
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6 wires on that harness for the display.   two of which are power and ground.  that would lead me to believe that it's a serial lcd?
That leaves 4, way more than required for a serial interface unless they use hardware handshaking.

Sniffing this would be a piece of cake IF you have a logic analyzer. If you don't you'd have to write something for your Arduino to do the job and that will be a task. That said there is at least one logic-analyzer-on-an-Arduino project around, I even think there was a post about it recently. I think it works with the SUMP client on your PC. That would make life easier.

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Rob
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6 wires on that harness for the display.   two of which are power and ground.  that would lead me to believe that it's a serial lcd?
That leaves 4, way more than required for a serial interface unless they use hardware handshaking.

Sniffing this would be a piece of cake IF you have a logic analyzer. If you don't you'd have to write something for your Arduino to do the job and that will be a task. That said there is at least one logic-analyzer-on-an-Arduino project around, I even think there was a post about it recently. I think it works with the SUMP client on your PC. That would make life easier.

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Rob

thanks for the input.   If i decide this is within my skillset, I would be purchasing a logic analyzer, possibly the one that is an arduino shield but more then likely one of these two (unless there are better options):
http://dangerousprototypes.com/docs/Open_Bench_Logic_Sniffer
but leaning towards this one:
http://www.sparkfun.com/products/8938
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I have no experience with the DP logic sniffer but I have the 8-bit Saleae (there's a 16-bit version as well now) and it's fantastic. Their support is good as well.

Last time I looked at the DP gadget it used Sump as the PC software, that is nowhere near as flash as the Saleae application.

Every time LAs are mentioned here a couple of us wax lyrical about how good the Saleae is.

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Rob
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g

it looks to have a 10 wire harness.   

i took it apart and noticed that the 4 buttons on the front panel had a handy 5 pin header and socket.  (4 buttons, 1 common ground) 



this leads me to believe that the button presses are not serial and and the connect directly to digital inputs on the master module.   that would leave 6 wires on that harness for the display.   two of which are power and ground.  that would lead me to believe that it's a serial lcd?
 (edit:  i contacted the person who made that and the buttons do extend out from that wire harness.)



The one thing that i'm still trying to research is how to reverse engineer something using the logic analyzer.  I'm very new to this and admittedly confused at how to interpret the output from the L.A. into something that i can work with
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Basically you just identify the GND wire, connect that to the LA GND then hook the LA inputs to the other wires and start pressing buttons. Hopefully a pattern will become obvious. If not post a screen shot here and maybe we can figure it out.

Also make sure the voltages involved are not too high for the LA.

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Rob
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Basically you just identify the GND wire, connect that to the LA GND then hook the LA inputs to the other wires and start pressing buttons. Hopefully a pattern will become obvious. If not post a screen shot here and maybe we can figure it out.

Also make sure the voltages involved are not too high for the LA.

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Rob

great.  thank you for all your insight.  I find all of your posts very helpful.  I'm going to finish up with my current code clean it up then i'll venture into this project. 
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I just got a Open Logic sniffer, its not awesome, its not crap either, functions well enough to use ... wouldn't brag over it though.

Spent more time fussing with it than using it sofar (the whole 4 days its been here), and am still getting some noise n echos on unused lines, but at the end of the day I got it for free, and I have no other LA so its fine.

and yea the java clients are kind of meh compared to what I have seen out there
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and am still getting some noise n echos on unused lines

could you just ground those lines?
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yea but if I want to watch 2 lines I gotta hook up a minimum of 9 wires ... I am just going to end up getting some 100K+ sip resistors and pull them down as someone on the DP forums did and be done with it
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i have the open bench logic analyzer, and a saleae logic analyzer clone. and frankly i love them both. the open bench can be picky at times, it gets frustrating to use sometimes, but it can pick up signals way faster than the saleae. the saleae i use however is much better for intercepting long, slower communications, as it does not buffer the whole recording on itself, it's more of a streaming type mechanism.
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I also have the open logic sniffer and like it more than the other posters.  The fact that it costs $50 (don't buy from Sparkfun for $70) is a factor in that.  It's pretty darn useful, though.  The client code could be better but it does what it's supposed to do.  I don't mind that it downloads the data when the capture is done.  It's pretty quick for that. 

On the issue of echos on the unused lines.  This is a problem because?  Like you don't like seeing them on the display?   They are pretty innocuous.  I have a stripped piece of wire with a clip on the end to which I attach all the unused probes and then clip to ground.  I like it more because it keeps my probes from flopping around, though, and often don't bother with ground.

I think it's a great LA for learning about LAs.
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