On 12/1/2014 2:18 AM, Jasen Betts wrote:> On 2014-11-30, Don Y <this@is.not.me.com> wrote: >> The traditional RJ45 8P8C doesn't seem like it would fare well in >> the environment and would also be tedious to machine *into* the >> case. > > http://www.ttabconnectors.com/pdf/AB_Specification_610_Issue_2.pdf > > possibly overkill, but those sort of things are available from several > vendors, > > be sure to use UV resistant cable,They're reasonably sheltered locations but, out here, the sun cooks *everything*. E.g., unpainted PVC pipe will turn BLACK from exposure.>> Abandoning it for a more physically convenient connector >> leaves me uncertain as to how "untwisting" all those connections >> *at* the connector would compromise the signal path. > > St 10Mbps, the signals are 10m long (manchester coding: 2 signals per > bit) you can untwist quite a bit before it hurts enough to stop > working.I'd really, really, really like to stick with 100Mb and a "traditional" hardware interface. It's a significant compromise to move away from it (but do-able). Joe's comments re: PHY capabilities are encouraging. I'm just not sure I can "guarantee" performance (changing a design after release is painful :< )
RJ45/8P8C alternatives
Started by ●November 30, 2014
Reply by ●December 4, 20142014-12-04
Reply by ●December 4, 20142014-12-04
On 11/30/2014 10:14 AM, Maynard A. Philbrook Jr. wrote:> In article <m5fhlv$d26$1@speranza.aioe.org>, this@is.not.me.com says... >> >> Hi, >> >> I have an irregular-shaped (metal) enclosure to which an ethernet connection >> must be mated. >> >> I can afford to run at 10BaseT speeds -- though would REALLY REALLY prefer >> 100BaseTX (-T2 is not a practical option). >> >> Connection must be weather-resistant (sheltered location; not "indoor"). >> >> The challenge is coming up with a suitable connection without requiring >> new castings. There are some tight physical space limitations that >> effectively rule out anything "revolutionary". >> >> The traditional RJ45 8P8C doesn't seem like it would fare well in >> the environment and would also be tedious to machine *into* the >> case. Abandoning it for a more physically convenient connector >> leaves me uncertain as to how "untwisting" all those connections >> *at* the connector would compromise the signal path. > > We've used M12 6 and 8 pin water tight connectors for that. They work > just fine from what we've found and much cheaper than getting the ones > already out here.Thanks, I'll look into that. I'm just not sure how to stress test this aspect of the design -- nor how to document how the connectors should be "wired" (i.e., detailed physical placement of each conductor). When you look at some of the BFM in high speed cabling (SCSI, enet, etc.)...
Reply by ●December 4, 20142014-12-04
Hi Joe, On 11/30/2014 4:32 PM, Joe Gwinn wrote:>> The traditional RJ45 8P8C doesn't seem like it would fare well in >> the environment and would also be tedious to machine *into* the >> case. Abandoning it for a more physically convenient connector >> leaves me uncertain as to how "untwisting" all those connections >> *at* the connector would compromise the signal path. > > Look for industrial ethernet solutions from such as Black Box. One way > to search is to require DIN rails, even if you don't need them.<frown> It seems like every "ruggedized" RJ45 just makes the mounting problem more tedious. Other than RJ45's "on pigtails", it seems like my only practical solution is a different connector body entirely. I'm going to play with some of the connectors suggested, here -- as well as some run-of-the-mill connectors -- to see just how sloppy I can get with fabrication before signal degradation becomes an issue.
Reply by ●December 4, 20142014-12-04
On Wed, 03 Dec 2014 23:18:34 -0700, Don Y wrote:> Hi Joe, > > On 11/30/2014 10:27 AM, Joe Chisolm wrote: >> On Sun, 30 Nov 2014 09:46:51 -0700, Don Y wrote: >> >>> I have an irregular-shaped (metal) enclosure to which an ethernet >>> connection must be mated. > >>> Connection must be weather-resistant (sheltered location; not >>> "indoor"). >>> >>> The challenge is coming up with a suitable connection without >>> requiring new castings. There are some tight physical space >>> limitations that effectively rule out anything "revolutionary". >>> >>> The traditional RJ45 8P8C doesn't seem like it would fare well in the >>> environment and would also be tedious to machine *into* the case. >>> Abandoning it for a more physically convenient connector leaves me >>> uncertain as to how "untwisting" all those connections *at* the >>> connector would compromise the signal path. >> >> Modern PHYs are so much better than pulling the signal out of the crap. > > Do you think that true even on the deeply embedded devices? E.g., SoC's > with MAC & PHY on the same die as the processor? >A lot of them may use the same IP blocks but I would think yes, on die or separate would probably be close to the same performance. It would probably depend on what they cut out of the on die to reduce the area.>> As a point of reference, we have a product that has to switch between a >> front RJ45 and a back plane connector. There is a RJ45 on a backplane >> that feeds to a .156 Sullins edge connector. A board plugs into that >> and has about 10" of diff pair to a TI ethernet mux chip to a SMC >> LAN8720 phy and 100Mb is no problem. So we go cable->RJ45->edge >> connector->lan mux->phy > > So, *through* the edge connector is your "least controlled" point of > transmission? I.e., you still try to maintain signal integrity on > either side of that connection -- you're not *casually* treating the > signals past the connector(s)?That's true. The layout guy ran diff pairs between the connectors. I'm not sure about careful impedance control, I'd have to go back and look at the stackup to see exactly what he did. My point was there is a mobo RJ45 connector -> small patch cable -> backplane RJ45 -> edge connector -> card->lan mux->phy and everything works fine. Some day I'd like to take some cat5, re-twist to maybe every foot and test. I could fix the FW on the embedded system to force 100M or 10M and see what happens.> >> Can you do some type of a pigtail coming out of the box to a weather >> tight connector? Maybe: >> RJ45-5EWTP-CS-CBL-8I and RJ45-5EWTP-CB > > I've thought of the pigtail approach, etc. I'm just questioning whether > the RJ45 is "appropriate" in any form in this sort of environment. I.e., > I can see using a weatherproof/resistant RJ45 to allow COTS devices to > mate with it. > > But, given that this connection is dedicated to this device, can I avail > myself of other "more effective" means of connection? E.g., "serial > ports" started out behind DB25's... then DB9's... but you'll also find > them as "three pads on a PCB" in many places. Nothing about a "serial > port" (read: 100BaseTX) connection *requires* a particular connector!Try it. Take a patch cable, whack it in half and solder a DB9M and F in line. Run several GB of TCP traffic through it and watch the error counts. If you have access to the FW you could pull out more detail on what lower level errors you are seeing. The good thing about the RJ45 is it is the defacto "this is a ethernet port" to most people. A DB9, they will probably try and plug a serial port into it. -- Chisolm Republic of Texas
Reply by ●December 4, 20142014-12-04
Hi Joe, On 12/4/2014 12:51 PM, Joe Chisolm wrote:> On Wed, 03 Dec 2014 23:18:34 -0700, Don Y wrote: >> On 11/30/2014 10:27 AM, Joe Chisolm wrote: >>> On Sun, 30 Nov 2014 09:46:51 -0700, Don Y wrote: >>> >>>> I have an irregular-shaped (metal) enclosure to which an ethernet >>>> connection must be mated. >> >>>> Connection must be weather-resistant (sheltered location; not >>>> "indoor"). >>>> >>>> The challenge is coming up with a suitable connection without >>>> requiring new castings. There are some tight physical space >>>> limitations that effectively rule out anything "revolutionary". >>>> >>>> The traditional RJ45 8P8C doesn't seem like it would fare well in the >>>> environment and would also be tedious to machine *into* the case. >>>> Abandoning it for a more physically convenient connector leaves me >>>> uncertain as to how "untwisting" all those connections *at* the >>>> connector would compromise the signal path. >>> >>> Modern PHYs are so much better than pulling the signal out of the crap. >> >> Do you think that true even on the deeply embedded devices? E.g., SoC's >> with MAC & PHY on the same die as the processor? > > A lot of them may use the same IP blocks but I would think yes, on die or > separate would probably be close to the same performance.I'm not sure of that. E.g., does every ARM w/onboard PHY/MAC use the same implementation (i.e., is the IP licensed from ARM regardless of actual company doing the fab?)? And, are there differences between (e.g.,) a NatSemi design and an Intel one (and an ARM one)?> It would > probably depend on what they cut out of the on die to reduce the > area.Yes. "Tradeoffs" esp with an eye to keeping the "system" (SoC) at the right price point, power consumption, die size, etc. "Something for nothing" comes to mind... :<>>> As a point of reference, we have a product that has to switch between a >>> front RJ45 and a back plane connector. There is a RJ45 on a backplane >>> that feeds to a .156 Sullins edge connector. A board plugs into that >>> and has about 10" of diff pair to a TI ethernet mux chip to a SMC >>> LAN8720 phy and 100Mb is no problem. So we go cable->RJ45->edge >>> connector->lan mux->phy >> >> So, *through* the edge connector is your "least controlled" point of >> transmission? I.e., you still try to maintain signal integrity on >> either side of that connection -- you're not *casually* treating the >> signals past the connector(s)? > > That's true. The layout guy ran diff pairs between the connectors. I'm > not sure about careful impedance control, I'd have to go back and look at > the stackup to see exactly what he did. My point was there is a mobo RJ45 > connector -> small patch cable -> backplane RJ45 -> edge connector -> > card->lan mux->phy and everything works fine. Some day I'd like to take > some cat5, re-twist to maybe every foot and test. I could fix the FW on > the embedded system to force 100M or 10M and see what happens.Understood.>>> Can you do some type of a pigtail coming out of the box to a weather >>> tight connector? Maybe: >>> RJ45-5EWTP-CS-CBL-8I and RJ45-5EWTP-CB >> >> I've thought of the pigtail approach, etc. I'm just questioning whether >> the RJ45 is "appropriate" in any form in this sort of environment. I.e., >> I can see using a weatherproof/resistant RJ45 to allow COTS devices to >> mate with it. >> >> But, given that this connection is dedicated to this device, can I avail >> myself of other "more effective" means of connection? E.g., "serial >> ports" started out behind DB25's... then DB9's... but you'll also find >> them as "three pads on a PCB" in many places. Nothing about a "serial >> port" (read: 100BaseTX) connection *requires* a particular connector! > > Try it. Take a patch cable, whack it in half and solder a DB9M and F in > line. Run several GB of TCP traffic through it and watch the error > counts. If you have access to the FW you could pull out more detail on > what lower level errors you are seeing.I think it might be easier (more deterministic) to just set up a producer that continually emits UDP packets (easier to do at a high rate) having a particular, known, sequential content. Then, a consumer that looks for these packets and *expects* them to have the particular content. So, it sees *all* the traffic and not only "knows" what it should be but *where* it should be [Obviously, arrange for a pair of these, back-to-back, so you can run FDX tests] ("Hmmm... there should have been another UDP packet right *here* and its contents should have been XXXX. As there is no elastic store *in* the cable, the PHY must have failed to recognize the start of the packet!") But, all this will ever tell me is that it adds (at least) some number of errors to a comm stream. It wouldn't let me know, for sure, if it would be AS reliable in all deployment cases. (i.e., the absence of errors doesn't mean there never WILL be any attributable to this hack) I'd also have to drag out a much longer length of cable and simulate the types of RF/EM environments it would encounter to get a *real* handle on the cost/compromise.> The good thing about the RJ45 is it is the defacto "this is > a ethernet port" to most people. A DB9, they will probably try and > plug a serial port into it.Yup. Adopting some other connector implies protecting against misapplication -- or, picking something sufficiently unique (given the application domain) that nothing comparable would likely be encountered *in* that deployment. [I rescued what I casually assumed to be a wide SCSI cable (colloquially "SCSI 3") a few weeks back. When I finally sat down to look at it, I noticed the connectors on each end were *female*! Ooops!]
Reply by ●December 4, 20142014-12-04
Den s=F8ndag den 30. november 2014 17.47.03 UTC+1 skrev Don Y:> Hi, >=20 > I have an irregular-shaped (metal) enclosure to which an ethernet connect=ion> must be mated. >=20 > I can afford to run at 10BaseT speeds -- though would REALLY REALLY prefe=r> 100BaseTX (-T2 is not a practical option). >=20 > Connection must be weather-resistant (sheltered location; not "indoor"). >=20 > The challenge is coming up with a suitable connection without requiring > new castings. There are some tight physical space limitations that > effectively rule out anything "revolutionary". >=20 > The traditional RJ45 8P8C doesn't seem like it would fare well in > the environment and would also be tedious to machine *into* the > case. Abandoning it for a more physically convenient connector > leaves me uncertain as to how "untwisting" all those connections > *at* the connector would compromise the signal path.wall mount RJ45 are just punch down so a couple of cm shouldn't break anyth= ing http://hyperline-cables.com/img/sharedimg/plugs/rj45-s-02.jpg how about neutrik? only needs a round hole and two screws http://sigma.octopart.com/180397/image/Neutrik-NE8MC.jpg -Lasse
Reply by ●December 4, 20142014-12-04
On Wed, 03 Dec 2014 23:18:34 -0700, Don Y <this@is.not.me.com> wrote:> >But, given that this connection is dedicated to this device, can I >avail myself of other "more effective" means of connection? E.g., >"serial ports" started out behind DB25's... then DB9's... but you'll >also find them as "three pads on a PCB" in many places. Nothing >about a "serial port" (read: 100BaseTX) connection *requires* a >particular connector!Well TIA-568 does require particular connectors, IEC 60603 in fact.=20 Now if you wish to argue that, TIA-568 is only moderately expen$ive. ?-) =20
Reply by ●December 4, 20142014-12-04
On Thu, 04 Dec 2014 13:51:56 -0600, Joe Chisolm <jchisolm6@earthlink.net> wrote:> >> So, *through* the edge connector is your "least controlled" point of >> transmission? I.e., you still try to maintain signal integrity on >> either side of that connection -- you're not *casually* treating the >> signals past the connector(s)? > >That's true. The layout guy ran diff pairs between the connectors. I'm >not sure about careful impedance control, I'd have to go back and look =at>the stackup to see exactly what he did. My point was there is a mobo =RJ45>connector -> small patch cable -> backplane RJ45 -> edge connector -> >card->lan mux->phy and everything works fine. =20>Some day I'd like to take >some cat5, re-twist to maybe every foot and test. =20^^^^^^^^^^^^^^^^^^^^^^^^^^^^>I could fix the FW on >the embedded system to force 100M or 10M and see what happens.Wow, that would be a significant twist reduction from the original cable. ?-) =20
Reply by ●December 4, 20142014-12-04
On Thu, 04 Dec 2014 16:10:52 -0800, josephkk wrote:> On Thu, 04 Dec 2014 13:51:56 -0600, Joe Chisolm > <jchisolm6@earthlink.net> wrote: > > >>> So, *through* the edge connector is your "least controlled" point of >>> transmission? I.e., you still try to maintain signal integrity on >>> either side of that connection -- you're not *casually* treating the >>> signals past the connector(s)? >> >>That's true. The layout guy ran diff pairs between the connectors. I'm >>not sure about careful impedance control, I'd have to go back and look >>at the stackup to see exactly what he did. My point was there is a mobo >>RJ45 connector -> small patch cable -> backplane RJ45 -> edge connector >>-> card->lan mux->phy and everything works fine. > >>Some day I'd like to take >>some cat5, re-twist to maybe every foot and test. > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > >>I could fix the FW on >>the embedded system to force 100M or 10M and see what happens. > > Wow, that would be a significant twist reduction from the original > cable. > > ?-)I figure if you are going to break it, go all out.... For short runs, say under 10ft, wonder what you can get away with. I would never put it in a product like that but would be fun to try anyway. -- Chisolm Republic of Texas
Reply by ●December 5, 20142014-12-05
On Sun, 30 Nov 2014 12:14:43 -0500, "Maynard A. Philbrook Jr." <jamie_ka1lpa@charter.net> wrote:>In article <m5fhlv$d26$1@speranza.aioe.org>, this@is.not.me.com says... >> >> Hi, >> >> I have an irregular-shaped (metal) enclosure to which an ethernet connection >> must be mated. >> >> I can afford to run at 10BaseT speeds -- though would REALLY REALLY prefer >> 100BaseTX (-T2 is not a practical option). >> >> Connection must be weather-resistant (sheltered location; not "indoor"). >> >> The challenge is coming up with a suitable connection without requiring >> new castings. There are some tight physical space limitations that >> effectively rule out anything "revolutionary". >> >> The traditional RJ45 8P8C doesn't seem like it would fare well in >> the environment and would also be tedious to machine *into* the >> case. Abandoning it for a more physically convenient connector >> leaves me uncertain as to how "untwisting" all those connections >> *at* the connector would compromise the signal path. > >We've used M12 6 and 8 pin water tight connectors for that. They work >just fine from what we've found and much cheaper than getting the ones >already out here. > >JamieI second this. At 10/100baseT speeds, we talk about less than 100 MHz frequencies, with a full wavelength wavelength in a twisted pair cable is 2 m. Anything above 1/10 wavelengths should be treated as a transmission line. Shorter connections than that can be handled as simple RCL modeling. Unwrapped wires in a M12 conductor are far shorter than that. Of course for 10GbaseT would not be an optimal solution.
