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<DIV>This has been an interesting discussion, but perhaps a bit of history
would</DIV>
<DIV>help. The original I2C protocal was developed by Philips to
interconnect</DIV>
<DIV>HIFI equipment together and still be able to use a 3 connector plug.
It was</DIV>
<DIV>designed for short distances, perhaps 10 feet max.</DIV>
<DIV> </DIV>
<DIV>To go further the normal “standard” is to use RS 485 (or RS 422)
standard. This</DIV>
<DIV>uses three wires, a ground, and two signal wires that are opposite of each
other.</DIV>
<DIV>So when the TX+ sends a “1”, the TX- sends a “0”. The wires are also
terminated</DIV>
<DIV>usually with a 120 ohm resistor on both ends. Thou some ignore this
rule.</DIV>
<DIV> </DIV>
<DIV>RS-485 can go thousands of feet. I have set up systems with the
length of over</DIV>
<DIV>4000’ between the controller and the node. </DIV>
<DIV> </DIV>
<DIV>Speed is based on distance, the major limitation is the “capacitance of the
wire”. This</DIV>
<DIV>will cause the leading and falling edge to degrade and limit the speed to
around 10KHz</DIV>
<DIV>for long distances. Shorter distances (100’) can get up to 1
MHz.</DIV>
<DIV> </DIV>
<DIV>The problem thou is this is one way communications at a time. Think
of it like the</DIV>
<DIV>old CB radios. You send a packet to the “good old boy” at the end
node and say “Over”</DIV>
<DIV>so the end node can respond back.</DIV>
<DIV> </DIV>
<DIV>RS 422 eliminates this by having separate xmit and rec pairs. </DIV>
<DIV> </DIV>
<DIV>In either case, the RS485 IC are reasonable priced and there are even
standards for</DIV>
<DIV>the connectors and connections.</DIV>
<DIV> </DIV>
<DIV>Fred Ebeling</DIV>
<DIV>ECP Designs</DIV>
<DIV> </DIV>
<DIV> </DIV>
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<DIV> </DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=triembed@triembed.org
href="mailto:triembed@triembed.org">Charles McClelland via TriEmbed</A> </DIV>
<DIV><B>Sent:</B> Wednesday, September 30, 2015 1:54 PM</DIV>
<DIV><B>To:</B> <A title=triembed@triembed.org
href="mailto:triembed@triembed.org">triembed@triembed.org</A> </DIV>
<DIV><B>Subject:</B> [TriEmbed] I2C range extension (Chip
McClelland)</DIV></DIV></DIV>
<DIV> </DIV></DIV>
<DIV
style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>
<DIV>Charlie, </DIV>
<DIV> </DIV>
<DIV>I agree with John’s recommendations but wanted to pass on my
experience. I can reliably go 8’ with i2c under the following
conditions:</DIV>
<DIV><SPAN class=Apple-tab-span style="WHITE-SPACE: pre"></SPAN>- Cat5 cable and
paying attention to which pairs are used for SDA / SCL</DIV>
<DIV><SPAN class=Apple-tab-span style="WHITE-SPACE: pre"></SPAN>- Speed set to
100kHz </DIV>
<DIV><SPAN class=Apple-tab-span style="WHITE-SPACE: pre"></SPAN>- 4.7k pull-ups
to 3.3V</DIV>
<DIV> </DIV>
<DIV>I need to get to 50’ so I have ordered a few <SPAN
style="FONT-FAMILY: arial, helvetica, sans-serif; WHITE-SPACE: nowrap; BACKGROUND-COLOR: rgb(238,238,238)">P82B715
</SPAN>chips. These chips advertise to get to 50’ but only if you are
using 5V logic so we will see if they can go 50’ at 3.3V. I will share my
results at the next meeting.</DIV>
<DIV> </DIV>
<DIV>Hope this helps,</DIV>
<DIV> </DIV>
<DIV>Chip</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>
<BLOCKQUOTE type="cite">
<DIV>On Sep 30, 2015, at 1:00 PM, <A
href="mailto:triembed-request@triembed.org">triembed-request@triembed.org</A>
wrote:</DIV>
<DIV> </DIV>
<DIV>Send TriEmbed mailing list submissions to<BR><SPAN class=Apple-tab-span
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replying, please edit your Subject line so it is more specific<BR>than "Re:
Contents of TriEmbed digest..."<BR><BR><BR>Today's Topics:<BR><BR> 1.
Re: Bulk LED Order (Adam Haile)<BR> 2. I2C range extension (Charles
West)<BR> 3. Re: I2C range extension (John
Vaughters)<BR><BR><BR>----------------------------------------------------------------------<BR><BR>Message:
1<BR>Date: Tue, 29 Sep 2015 13:58:17 -0400<BR>From: Adam Haile
<email@adamhaile.net><BR>To: "triembed@triembed.org"
<triembed@triembed.org><BR>Subject: Re: [TriEmbed] Bulk LED
Order<BR>Message-ID:<BR><SPAN class=Apple-tab-span
style="WHITE-SPACE: pre"></SPAN><CAG8g-TaEQgjJRs4GGKhWiMPj-NTKE_iUxbLXbdqY-6z6Nn0fTQ@mail.gmail.com><BR>Content-Type:
text/plain; charset="utf-8"<BR><BR>Final call! Putting in quote request
tomorrow. Let me know if you want<BR>anything.<BR><BR>On Fri, Sep 11, 2015 at
11:14 AM, Adam Haile <email@adamhaile.net> wrote:<BR><BR>
<BLOCKQUOTE type="cite">I recently had to tear down my old porch lighting
install when we had our<BR>house repainted, so I'm going to be ordering a
bunch of new lights from my<BR>supplier in China.<BR><BR>Like last time, if
anyone wants to get in on the order, the pricing is a<BR>huge discount from
normal suppliers like Adafruit, Sparkfun, Amazon, eBay,<BR>etc.<BR><BR>I
don't take a profit, the prices in the pricing lists (GDrive link
below)<BR>are direct from the manufacturer. The major point here is to save
on<BR>shipping for everyone. Which I'll divide between all buyers based on
the<BR>percentage of the overall purchase price which is
yours.<BR><BR>Pricing lists
here:<BR><BR>https://drive.google.com/folderview?id=0B7a_WsLpan5-SEl5TjAtTjctZm8&usp=sharing<BR><BR>So,
if you would like anything, please let me know in the next couple
of<BR>weeks and give me the exact model number and quantity. Most things
come in<BR>5m rolls, so you can tell me rolls or meters.<BR><BR>Once I get
everyone's details I'll will request a final quote (some of the<BR>pricing
can vary by quantity) and then send everyone their final
cost.<BR><BR>*PLEASE NOTE*: Since I have to pay the manufacturer via PayPal,
you *MUST* pay<BR>me via Paypal. That way no money has to go through my own
personal bank<BR>accounts first. So, sorry, no cash or checks. And payment
must go through<BR>prior to submitting the final order to the manufacturer.
Sorry if this is<BR>an inconvenience, but it's the easiest way for me to do
it.<BR><BR>Let me know.<BR><BR>Adam<BR><BR></BLOCKQUOTE>-------------- next
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2<BR>Date: Tue, 29 Sep 2015 22:03:01 -0400<BR>From: Charles West
<crwest@ncsu.edu><BR>To: TriEmbed
<triembed@triembed.org><BR>Subject: [TriEmbed] I2C range
extension<BR>Message-ID:<BR><SPAN class=Apple-tab-span
style="WHITE-SPACE: pre"></SPAN><CAGojqSk0_4x63vjm0EhqRag56fW9y38j9qfJzOF8sRwzW_tfLQ@mail.gmail.com><BR>Content-Type:
text/plain; charset="utf-8"<BR><BR>Hello,<BR><BR>Thanks again for all the good
discussion on electrical connectors.<BR><BR>We're still debating some of the
specifics for the CANInstall and/or<BR>I2CPotential protocols. One of
the big things up in the air is how<BR>reliable I2C is and how long the range
can be.<BR><BR>My impression is that having a I2C bus of more than a meter or
two is<BR>considered pushing your luck. However, there seem to be
range<BR>extender/repeater chips available that promise rather drastically
improved<BR>range (such as the P82B715).<BR><BR>If I may ask, what is the
longest I2C bus you have built/seen?<BR><BR>How has your experience been in
terms of reliability?<BR><BR>What sort of bus speeds do you tend to
use?<BR><BR>The bus speed is driven by the master, so theoretically you could
have a<BR>sub-hertz baud rate? Does this mean that you could get a
really long range<BR>with a super slow baud rate or are the edges not sharp
enough to be<BR>detected?<BR><BR>Thanks,<BR>Charlie<BR>-------------- next
part --------------<BR>An HTML attachment was scrubbed...<BR>URL:
<http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20150929/064d0dab/attachment-0001.html><BR><BR>------------------------------<BR><BR>Message:
3<BR>Date: Wed, 30 Sep 2015 12:54:03 +0000 (UTC)<BR>From: John Vaughters
<jvaughters04@yahoo.com><BR>To: Charles West <crwest@ncsu.edu>,
TriEmbed <triembed@triembed.org><BR>Subject: Re: [TriEmbed] I2C range
extension<BR>Message-ID:<BR><SPAN class=Apple-tab-span
style="WHITE-SPACE: pre"></SPAN><1421720024.2476926.1443617643320.JavaMail.yahoo@mail.yahoo.com><BR>Content-Type:
text/plain; charset=UTF-8<BR><BR>Charlie,<BR><BR>The biggest problem I would
be concerned about on i2c over a long distance is noise susceptibility that
could affect reliability. So the importance of reliable communication is at
question. I guess the first question would be, do you have an environment that
is noisey? Then, Do you care if you have interruptions? If your environment is
fairly clean of noise and you can live with communication interruptions, then
long i2c may be a good low cost solution for long runs. <BR><BR>Here is what
you may want to consider. <BR><BR>1. Take control of the pull up resistors by
disabling them on the chip.<BR>2. Tune the pull up resistors by starting at a
safe low level and then increase them until you stop getting communication at
the length you are running. Then back down. Keep in mind that you will gain
more reliability as you reduce the pull ups.<BR>3. Twisted pair cables would
be your first attack on noise.<BR>4. If you still encounter noise, consider
ferrite beads to supress. This is best done if you have an idea of the noise
frequency. <BR><BR>The alternative is if you truly desire reliable
communications, then 485/CAN is the way to go. CAN being the most expensive,
but gives you the similar capability to i2c with the ad hoc interruption
communication capability. Or better stated an adhoc like network with a
priority assignment.<BR><BR>I personally never ran i2c that long and cannot
answer those questions. I generally have used 485 the most. The TI chips are
usually the lowest cost for communication. For some reason people love the
half duplex, but I prefer the full duplex.<BR><BR>I would be curious to know
how far you make i2c run if you go that route.<BR><BR>John
Vaughters<BR><BR><BR><BR>On Tuesday, September 29, 2015 10:03 PM, Charles West
via TriEmbed <triembed@triembed.org>
wrote:<BR><BR><BR><BR>Hello,<BR><BR>Thanks again for all the good discussion
on electrical connectors. <BR><BR>We're still debating some of the specifics
for the CANInstall and/or I2CPotential protocols. One of the big things
up in the air is how reliable I2C is and how long the range can be.<BR><BR>My
impression is that having a I2C bus of more than a meter or two is considered
pushing your luck. However, there seem to be range extender/repeater
chips available that promise rather drastically improved range (such as the
P82B715). <BR><BR>If I may ask, what is the longest I2C bus you have
built/seen?<BR><BR>How has your experience been in terms of
reliability?<BR><BR>What sort of bus speeds do you tend to use?<BR><BR>The bus
speed is driven by the master, so theoretically you could have a sub-hertz
baud rate? Does this mean that you could get a really long range with a
super slow baud rate or are the edges not sharp enough to be
detected?<BR><BR>Thanks,<BR>Charlie<BR><BR>_______________________________________________<BR>Triangle,
NC Embedded Computing mailing
list<BR>TriEmbed@triembed.org<BR>http://mail.triembed.org/mailman/listinfo/triembed_triembed.org<BR>TriEmbed
web site:
http://TriEmbed.org<BR><BR><BR><BR>------------------------------<BR><BR>Subject:
Digest
Footer<BR><BR>_______________________________________________<BR>TriEmbed
mailing
list<BR>TriEmbed@triembed.org<BR>http://mail.triembed.org/mailman/listinfo/triembed_triembed.org<BR><BR><BR>------------------------------<BR><BR>End
of TriEmbed Digest, Vol 28, Issue
31<BR>****************************************<BR></DIV></BLOCKQUOTE></DIV><BR>
<P>
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_______________________________________________<BR>Triangle, NC Embedded
Computing mailing
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