I’ve sent out a Digi One IAP, and the reports from the field are that it won’t power up when connected to a Cisco 3560-24PS. They’ve tested the switch port with an IP phone, which worked. Has anyone tried to power the Digi One IAP with PoE?
I don’t have an injector to test with, but I’m considering one of the DIY PoE injector circuits.
Update: the Digi One IAP did not work with a PoE injector. The IP phone that did work was a Cisco 960G.
I love the PoE option for the Digi One IAP. I am currently using it to power 21 devices connected to AB & TI plcs in an injection molding enviroment. While I am sure power was available from the injection molding machine, convincining maintence; then having them find the time was another matter. Just installed a 3 com PoE and all is fine. I think there are 2 versions of PoE (endspan, midspan). I do not remember what Digi uses. The 3 com PoE is not integrated to a switch it is strictly power.
Cisco started selling PoE BEFORE the IEEE standard existed and their pinouts are a little different.
Recent Cisco switches auto-detect and use EITHER PoE method. Reason being that all the older Cisco IP phones use the Cisco-proprietary PoE technique and they didn’t want to upset their customers any more than necessary.
The problem probably isn’t the IAP. It’s your Cisco switch, which is pre-IEEE PoE standard.
The Digi IAP should work fine with PoE. Keep in mind that the DOIAP supports mid-span only, and the Cisco defaults to end-span which we do not support at this time.
I spoke with a customer yesterday, and Cisco Support had given him a series of commands, which switched the Cisco from end-span to mid-span. Unfortunately the customer did not document the commands
That is very possible. Powered Ethernet evolved from several competing vendor standards that were merged under 1 banner. I am not “up” on the jargon, but the Digi One IAP hardware design only supports 1 of the methods, which is the application of power to the unused wires in the UTP cable. Likely the Cisco in question is supplying power over the active Ethernet wire pairs.
Can you provide any more detail on exactly how 802.3af non-compliant the Digi One IAP is? I’m looking at http://standards.ieee.org/getieee802/download/802.3af-2003.pdf and it’s pretty clear that a powered device must accept power over either pair. (“The PD shall be capable of accepting power on either of two sets of PI conductors.”)
Currently I’m running one with 48V bench power supplied connector to pins 4&5, ground on 7&8 (I think this is referred to as “Mode B”). The unit does power up and appear to function with this connection.
The other option, “Mode A”, is to provide power on pins 1&2, with ground on 3&6. (The active data lines).
I think the standard also requires that a device function with either polarity.
I’ll ask around; I am more an app engineer and not hardware designer. In the 3 years I’ve worked with the Digi DIN-rail product this is the first time I’ve heard of someone wanting PoE on it - I am not sure why this feature was even added other than the first product design was inheritted from a company absorbed by Digi before my time.
Digi is pulling PoE support out of most base products because it adds considerable cost that most purchasers don’t care about (adds like 15% to the cost). Instead we’ll offer a few special models with better PoE at a higher price.
Ironically, the Digi One SP is the only product I see very suited to PoE - and it one of the few without any PoE support even as an optional build. 
Thanks Lynn. (BTW, I’m almost certain I’ve prowled around your website recently…)
If I told you that in our application we removed the IAP from its DIN rail mount case, potted it in a sheet metal enclosure, and connected it inside a piece of battery powered equipment, maybe PoE would start to sound pretty good? 
Yeah, the Digi Connect ME would make more sense, especially considering the available space, but this time around I didn’t have time to spin a board and do PoE ourselves.
I’ve got a support request in; I guess I’ll save my doc and compliance gripes for them.
Are you using the screw terminals of the IA/IAP? The main value of the IA/IAP is the DIN-rail and DC-power isolation - neither of which you use. So it does sound like you’d be happier with Digi One/Connect SP-sized 802.3af solution.
Putting it into a battery system (especially if the battery is part of a network-centered UPS) does make sense for 802.3af support.
> Are you using the screw terminals of the IA/IAP? The
Kinda sorta. We removed all the connectors and DIP switches (!), so I soldered wire directly to the PCB pads for the terminal block connector. (Space limitations.)
> main value of the IA/IAP is the DIN-rail and DC-power
> isolation - neither of which you use. So it does
> sound like you’d be happier with Digi One/Connect
> SP-sized 802.3af solution.
Maybe…we looked at the SP, but it wasn’t clear that it would support the protocol conversion. In fact, I’m almost certain tech support told me to go with the IAP for conversion.
As I understand it:
Digi One IA–no protocol conversion.
Digi One IAP–protocol conversion.
Digi SP IA–no protocol conversion?
Is there a Digi SP IAP planned?
What’s the difference between the SP and SP IA? (Besides a DIN rail kit and power pigtail, the feature/spec list appears to be identical.)
We’re not always battery powered, but I doubt that I have the power budget to run an external converter. We’re also space limited.
Are you doing the Modbus Ethernet/Serial bridge?
Neither SP or SP-IA has any protocol conversion.
The newest Digi One IA firmware “G” has a reduced Modbus bridge function (but no Rockwell support). It matches the Modicon “CEV” functional spec - 12 clients instead of the 64 in the DOIAP. Plus a few other reductions for marketing reasons - plus no PoE support (the issue of cost). Technically, the SP, IA and IAP all have the exact same CPU, Flash, and RAM specs.
> Are you doing the Modbus Ethernet/Serial bridge?
Yep, Modbus/TCP to a serial connected Modbus/RTU slave.
Great - thanks for the feedback. I have been wondering if anyone uses PoE for IAP.
It is the “midspan” we support - which was the early favorite. But switch vendors have opted for the end-span since it doesn’t assume “unused pairs” are really unused I guess.
I asked around and Digi has an SP-sized unit with full 802.3af support (mid & end-span) in engineering test as we speak. This is the Digi Connect SP (not Digi One SP) so it supports custom NetOS development.
Other full 802.3af hardware will be coming as boards cycle thru respins.
Update: we bought a few midspan PoE injectors and made the customer happy. It isn’t as clean as powering straight from the PoE switch, but it does work.
Will there be any way to identify the fully compliant 802.3af hardware in the future?
Now that we’ve got the sucker running, I have some questions about tracing and serial port stats, but I think I’ll start a new thread for those.
Thanks once more!
> Other full 802.3af hardware will be coming as boards
> cycle thru respins.
Has this happened yet? I’ve got another PoE + Digi One IAP project, and it would be really nice to be able to skip the PoE midspan injectors this time around…
Not yet - likely very early in 2006. Our hardware team is stretched thin, plus we have a whole list of other things to adjust.
> Cisco started selling PoE BEFORE the IEEE standard
> existed and their pinouts are a little different.
Yep, we noticed that as well.
> The problem probably isn’t the IAP. It’s your Cisco
> switch, which is pre-IEEE PoE standard.
As I understand it, the IAP not supporting endspan/mode B PoE was the problem.
Do these newer Cisco switches support midspan and endspan PoE? From what I’ve seen, most PoE capable switches seem to only provide power on lines 1+2 and 3+6 (endspan/mode A).
Actually, I’ll start a new thread here … Fall 2006 this all will change.
Wingmaster,
is there any way to find out what those commands were that your referenced customer used? we have a number of these Digi PoE devices (with potentially much more needed) and would find this incredibily valuable if we could tell our gear to flip from end to midspan power delivery. We haven’t been able to find those commands and as far as I know, you can’t do it. Thank you.