Show Posts
Pages: [1]
1  Using Arduino / Networking, Protocols, and Devices / Re: Unexplained I2C "spikes" or "glitches" on: June 05, 2012, 01:36:27 pm
To follow up, I found the following link which probably explains what I'm seeing.  http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/717/t/186350.aspx

Based on the above link, I now suspect I'm seeing the bus being released at the end of a cycle - which is legal so long as scl is low.  So....it's probably software.  (grin)
2  Using Arduino / Networking, Protocols, and Devices / Re: Unexplained I2C "spikes" or "glitches" on: June 05, 2012, 11:16:40 am
Yea, I am also mostly concerned with the stand-alone spikes on the sda line which line up timing wise with the rising edge of the clock signal.

To your point, I was wondering about capacitance as well.  There is a breadboard in the loop - however, I took it out and ran one arduino directly to the other just to see if there was a change is these "spikes".  There was none....no change between the two setups.  Does anyone know if too much capacitance would cause this behavior?
3  Using Arduino / Networking, Protocols, and Devices / Re: Unexplained I2C "spikes" or "glitches" on: June 05, 2012, 10:30:00 am
Yes, that's an excellent article by Wayne - I've learned quite a bit from his post/s.

Taking off my external 3.2K pullups does make my waveforms uglier (per Wayne's post), but they do nothing to effect (literally no effect) these spikes as shown on the attachment.  Are you suggesting that pullups *should* affect these spikes?  If so, I'd love to learn more about why or how that would be as I'm still learning the ins and outs of this protocol.

Thanks!
4  Using Arduino / Networking, Protocols, and Devices / Unexplained I2C "spikes" or "glitches" on: June 05, 2012, 10:13:01 am
Hi all,

I'm trying to get two arduinos talking to each other via I2C.  The issue is that I get very repeatable "spikes" or "glitches" on my SDA line which happen to line up exactly with the clock's leading edge.  However, these "spikes" are not present the entire time - well, at least at that level....  (Take a look at the attachment for a trace)  Anybody know what might be causing this?

Suffice to say, these little buggers are causing for poor communications....

Mark
5  Using Arduino / Networking, Protocols, and Devices / Re: WIZnet W5100 + Uno Performance Expectations? on: April 14, 2012, 10:22:58 pm
Yes, I'm getting good performance on ping as well. Basically, on the Windows side, the entire delay is waiting for a response on the wire. On the. arduino side, everything from the point I get the message off SPI to the response is also fast. Frankly, I just can't figure it.  On the windows side, I'm waiting hundreds of milli seconds.

Is anyone else out there getting fast round trips?  Anything special about that setup?  Anyone else seen these slow speeds and found where exactly its slow?

Thanks all.

Mark
6  Using Arduino / Networking, Protocols, and Devices / WIZnet W5100 + Uno Performance Expectations? on: April 12, 2012, 09:47:53 am
All,

What kind of performance (in general) should I expect roundtripping a small packet (<20 bytes) from a pc to my Uno via the W5100 using the stock Arduino ethernet library?  Currently I'm only seeing 250-500 milli-second times which seems VERY slow.  Are my expectations out of wack?  What are y'all seeing?

My application is remote control of a tethered robot over cat5.  With those kinds of response times, it's too laggy to be reasonable.

If others of you out there are seeing much better performance, please let me know your configuration and I'll start digging more into my setup.  If I'm stuck with this lag, I'll probably just move to 485 and be done with it....  Who knows, it's probably Windows messing me up again.  (grin)

Thanks in advance for everyone's help.
Pages: [1]