I have a setup with a PoE Blox with a Gigablox nano. Connected to this is a SPEBlox which i use to communicate with another SPEBlox. If i run a Gigabit connection through the SPEBlox line alone i get full bandwidth. Similarly if i run it through only the PoEBlox i also get full bandwidth, but if i run the connection through both the PoEBlox and SPEBlox i get a lot of package loss and under half bandwidth. Do you have an idea of how to fix this?
Can you tell me how you connect between the PoEBlox and SPEBlox? A photo would be helpful of the full setup would be useful.
We used one of the twisted pairs cable from you to connect between the different units. I can connect through it with limited bandwidth and high packet loss, so I would assume the pins are correct.
That’s interesting. I don’t believe we’ve ever tested a PoEBlox and SPEBlox together. Have you tried all ports on PoEBlox?
Also, do you happen to have a GigaBlox Nano PicoConn or GigaBlox Nano RJConn to hand? Testing with that will help determine if the issue is related to the PoE circuitry on PoEBlox or not.
I think I have only tried two or three of the port, but I can check with all on Monday.
Unfortunately I don’t have any of the units you mention.
Do you think it has an effect if the SPEBlox connected on the switch side is configured as master or slave?
I’ve just reviewed the design and I believe I know what the issue is.
It’s related to the interconnection of the SPEBlox and PoEBlox. SPEBlox uses transformerless ethernet on the 1GBASE-T port, which means there is no galvanic isolation between the ethernet port on the the chip, and the connector.
GigaBlox and SPEBlox work well with a direct cable, and GigaBlox uses the same chip as GigaBlox Nano (which is the what is used on PoEBlox). Therefore I can conclude that the issue is definitely related between the PoE circuitry on PoEBlox and the transformerless ethernet port on SPEBlox. Without specifically testing the signals on the oscilloscope, I would say that the PoE circuitry on PoEBlox is trying to do load classification on the ethernet lines, and gets confused seeing the voltage on port from SPEBlox.
To solve this, we need to turn off PoE on the PoEBlox port you are connecting SPEBlox to. Unfortunately there’s no way to do that programmatically yet, as we have not released management firmware for PoEBlox yet (management firmware would allow PoE to be toggled on individual ports).
Are you open to removing some components from PoEBlox to manually disable PoE on one of the ports on SPEBlox? This would require some soldering.
That sounds interesting.
If you think it will fix the issue i am open to give it a try with removing the components.
Thanks for your response. After studying the design, we’ve realised it’s not possible to remove any of the PoE circuitry without turning POE off for all channels. That’s obviously not what want to achieve.
Can I ask you, is the SPEBlox on the using the same power and ground as PoEBlox? If not, there could be a ground loop issue as SPEBlox is transformerless and I just want to eliminate that.
I think the only way to solve this will be for us to release new firmware for PoEBlox that allows POE to be turned off selectively on specific ports. That will either be controllable via the UART port on PoEBlox, or it could just be static firmware that you flash that always turns off PoE on a specific port of your choice. That would solve your issue. The problem is that this will take around 3-4 weeks to deploy, given our current workload.
Does that work with your timeline?
One other workaround is to buy an ethernet isolator, which you can connect between SPEBlox and PoEBlox. This will add transformers inline, and isolate the two ports, which will also solve the issue. Of course this is not ideal.
We do have shared ground and power between the two units.
We preferably need a prototype ready sometime this week, so i have purchased a Ethernet isolator we will try to fit in our enclosure and hope that works for now until the firmware update is ready.
Ok, sounds good. Please let me know how you get on with that.
In the meantime I"ve put this (ability to power down individual PoE channels) into our development pipeline.