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'[EE] Re: Can You Identify the Mystery Protocol?'
On Fri, July 6, 2012 3:15 pm, John Hansen wrote:
I have not seen this protocol before, but this sure seems like a good
application for the "logic" analyzer: <http://www.saleae.com/logic/> This
has the combination of very deep memory and fast enough sampling so you
should be able to record and decode the protocol. I can loan you mine for
a short time if you're in the area (near Austin, TX), but the logic is
relatively cheap- just buy one!
(just a happy user of the logic)
Just outside of Austin, TX
The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with
On Fri, 6 Jul 2012 15:41:32 -0500 (CDT), you wrote:
A very handy trick when looking at 1-wire protocols is to add some series resistance to the line
(and pullups if it isn't open-drain) , so you can tell from slight differences in voltage levels
which end is talking at any time.
If things get really complex, you should be able to tweak the resistance, pullups and analyzer
input thresholds in such a way that you can get a clean, seperate signal for transmissions at each
end. Being able to tell who is talking when can go a long way to figuring out handshakes, acknowledges
etc. over a 1-wire bus
Isaac Marino Bavaresco
Most probably this bus uses open-drain drivers with a pull-up resistor.
Add a low-value resistor in series with the line to exacerbate any
voltage drop. This way you can connect one of your scope's probe to each
side of the resistor and then you will know when it is the master and
when it is the the microphone that are pulling the line low.
Possibly the microphone is pulling the line low after it sees the host
pulling it low. When the host releases the line, the microphone keeps it
low for the time it wishes, signaling a zero or a one.
If that's true, you will see small "steps" in the signal when the host
releases the line.
Em 6/7/2012 17:41, Matt Bennett escreveu:
Thanks for the suggestions. I had not thought about using a resistor in
the line. That's a clever strategy.
On Fri, Jul 6, 2012 at 5:12 PM, Isaac Marino Bavaresco <
yahoo.com.br> wrote: isaacbavaresco
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