Hello, I have been experiencing intermittent connection issue with my setup since I have started using the SPEBlox and GigaBlox combo from BotBlox.
For more details, in my test setup, I have a custom PCB that utilizes the 1G single-pair Ethernet (SPE). Hence, I am using SPEBlox and GigaBlox to connect the board to my control PC. The distance from the PCB to this setup varies from 5-meter to 30-meter using a custom cable depends on customer requirement. All other cables were bought from BotBlox for this setup (RJ45 ethernet, power, etc.) From the datasheet, it states that max transmission distance for 1000BASE-T1 is 40 meters so I assume it would be fine.
In recent testing, three different cable lengths were used and the outcomes were different. On a 5-m cable, the setup worked fine and the control PC can always ping to the PCB unit. However, on a 10-m cable, the connection could not establish at all and LED D12 did not blink. Then, I tested on a 20-m cable and the connection was intermittent. At some events it connected and the LED was blinking at the beginning but it started dropping after sometimes. And at other events, it did not connect at all and I had to power cycle everything couple times to bring it back.
I’m not sure what is causing this issue and would like to share with you to ask for your insights and your experience with it. Please let me know if you have any questions. Thank you!
@tung.nguyen Welcome to the forum!
That’s interesting, definitely sounds like a cabling issue. The 40 meter distance that the specification states isn’t really practical. The maximum range we’ve ever achieved on our boards is 22 meters on a 28AWG UTP. I spoke with the folks at TI about this and they’ve basically confirmed that their chips don’t really work up to 40 meters (yet).
With this in mind, 40 meters is more like the physical maximum limit, but the practical, real limit, on a real world cable, is more like 20 meters.
So it’s not super surprising that your 30 meter cable doesn’t work.
What kind of cable are you using? If it’s anything other than a 28AWG UTP, then performance will be worst. The lack of functionality at 10 meters in interesting and possibly some manifestation of reflections on the type of cable you’re using. Let me know your cable specifications and I can debug further.
Josh
Hi Josh,
Thank you for your response. For more information, I’m using a special custom cable with a single twisted pair of 24AWG cable included for this SPEBlox (see attached pictures). Do you think the issue is coming from this custom cable? It’s strange to me that its connection is intermittent between different lengths. Note that they are all the same cable type.
Have you had any experience testing the SPEBlox in similar form? Such as testing it in other conditions that is not using 28AWG UTP.
Best Regards,
Tung Nguyen.
It’s most likely the cable. SPE is best on 28AWG cable, like the kind used in CAT6 cables.
At 10 meters, what’s probably happening is that it’s a sweet spot where the reflections caused by the mismatch in cabling, interferes with the actual signal. This is to say, it’s not just a case of signal loss caused by increased distance. It’s the interplay of the reflections, the data rate, the length of the cable, and probably also the echo cancellation buffer length in the SPE PHY that causes data to be lost at some distances but not others.
Unfortunately on the current version of SPEBlox, there is no easy way to debug and spit out signal information. We are building a debug UART port onto the next revision of SPEBlox which will allow you to query the SPE PHY and check for signal parameters, but that’s not released yet.
Some of our customers have used Telebyte hardware (https://www.telebytespe.com/) to test their SPE cabling, as they supply full test solutions for SPE. It might be worth reaching out to them to see if they can assist.
