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I2C Decoding? — Parallax Forums

I2C Decoding?

everesteverest Posts: 141
edited 2010-08-31 02:36 in Accessories
Can the Propscope decode I2C signals? I'm finding myself working a lot with I2C chips and I'd really like to be able to see what's going on between those chips for troubleshooting purposes.

Thanks!

-Jeff

Comments

  • sylvie369sylvie369 Posts: 1,622
    edited 2010-08-23 06:45
    The PropScope has a logic analyzer that will show you the status of digital signals on up to four lines at once, which means that if you were to connect them to the SDA and SCL and you understood the I2C protocol, you could decode the signals as they appeared on your screen:

    This may be helpful, though it does use a scope that has special I2C triggering (which you should be able to replicate on the PropScope by picking out the trigger conditions yourself):

    http://www.parallax.com/dl/docs/article/i2cSystemswithHPScope.pdf

    Chapter 5 of the student manual that Andy Lindsay is writing has related information, showing step-by-step how to interpret synchronous serial communications (though not specifically I2C) using the PropScope. It's available here:

    http://forums.parallax.com/showthread.php?t=124294

    (self-promotion: ) If you're going to use it for this purpose you might want to put together a little connector like I made, which you can see here:

    http://forums.parallax.com/showthread.php?t=123627&page=2
  • everesteverest Posts: 141
    edited 2010-08-23 07:42
    Yea, I figures that was the case. I can follow the hi/low states on sda/scl but some of the other options with decoders are pretty tempting...just dumps out all the 1s ans 0s and ACK/NACKs. At a glance data checking is a pretty neat feature. I'm bummed the propscope doesn't support it.

    -Jeff
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-08-23 15:02
    everest wrote: »
    Yea, I figures that was the case. I can follow the hi/low states on sda/scl but some of the other options with decoders are pretty tempting...just dumps out all the 1s ans 0s and ACK/NACKs. At a glance data checking is a pretty neat feature. I'm bummed the propscope doesn't support it.

    Not to speak for him, but I'll bet you could convince Hanno that it should be added, eventually, at least. Unless I'm terribly confused, it's just a matter of software (a phrase most easily uttered by the person not responsible for writing that software).
  • everesteverest Posts: 141
    edited 2010-08-23 15:44
    Yes, I'm pretty sure it is. Those links you posted are EXCELLENT. That's one of the reasons I love Parallax stuff. . .the support and educational aspects are just head and shoulders above anything else available.

    I'm generally only talking about a few bytes of I2C data, so decoding things manually, just for troubleshooting, shouldn't really be a huge hassle.

    Thanks! Now off to order my PropScope :)

    -Jeff
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-08-23 15:50
    everest wrote: »
    Yes, I'm pretty sure it is. Those links you posted are EXCELLENT. That's one of the reasons I love Parallax stuff. . .the support and educational aspects are just head and shoulders above anything else available.

    Yeah, 1-1/2 years ago or so, I was happy to be able to make an LED blink. I'm used to paying a LOT more for this kind of education.
  • HannoHanno Posts: 1,130
    edited 2010-08-25 13:59
    Hi Jeff,
    Serial protocol analysis/triggering has been on the #2 position of my "todo" list for too long now... All the infrastructure is there in the viewport library that propscope is built on- but I want to do it right. Once Andy's book is finished I'll start.

    In the mean time- please list the features- and ideally post screenshots of other scopes to show me what you want PropScope to do...
    Hanno
  • Shawn LoweShawn Lowe Posts: 635
    edited 2010-08-26 07:40
    Hanno wrote: »
    Hi Jeff,
    Serial protocol analysis/triggering has been on the #2 position of my "todo" list for too long now... All the infrastructure is there in the viewport library that propscope is built on- but I want to do it right. Once Andy's book is finished I'll start.

    In the mean time- please list the features- and ideally post screenshots of other scopes to show me what you want PropScope to do...
    Hanno

    Hanno- you are the man!
  • everesteverest Posts: 141
    edited 2010-08-26 07:46
    Hanno,

    This is great news. . .do you maintain/build the software that runs the Propscope? Is there something other than the Parallax software I'd need to load to use your stuff?

    Long story short, I'm probably not experienced enough to provide a lot of useful feature recommendations, but I was looking at these kinds of screens while choosing a logic analyzer/Oscope:

    http://www.usbee.com/axdec.html (this one isn't my favorite)

    I prefer the simplicity of this one:

    http://www.linkinstruments.com/mso19f.htm

    Very nice and clear. . .ACKs/NACKs and the data translated into the individual bits. . .super!

    -Jeff
  • HannoHanno Posts: 1,130
    edited 2010-08-26 12:53
    Yes, I developed the PropScope firmware and software. PropScope is built on the ViewPort library- which I also developed. Check out more information on both- and my other projects here:

    http://hannoware.com

    I'm not terribly excited about either of the screenshots you linked to... It needs to be both easier to use and more powerful. Better graphics is good too- as long as it keeps things simple and beautiful. We'll get there... What protocols should it support? I2C, SPI, RS232, MIDI, maybe even USB?

    Hanno
  • everesteverest Posts: 141
    edited 2010-08-26 14:15
    If you have I2C support, does that suppose SMBus would be decoded as well? Sorry, I'm a bit of a newbie, but I do deal with SMBus devices as well.

    -Jeff
  • dnalordnalor Posts: 222
    edited 2010-08-27 12:24
    Must have: I2C, SPI, RS232
    Maybe: CAN

    I searched for screenshots.
    Found this: http://tmetrix.com/downloads/seminars/LeCroy_Serial_data%20_June_08.pdf
    It should be something like in the screenshots in this presentation.
    Decoded data direct under/over the signal.

    SMBus: http://www.maxim-ic.com/app-notes/index.mvp/id/476
  • HannoHanno Posts: 1,130
    edited 2010-08-31 02:36
    Thanks Dnalor for the nice screenshots- that's pretty close to what I hope to achieve- including the triggers...
    Hanno
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