PoE problems with TX2012R-P

Finally I understood what is the problem with some Mikrotik stuff.

On Mikrotik datasheet of CCR1009-7G-1C-1S+PC routerboard was reported Passive 54v but no specification what pin of ethernet cable it use to transmit power. After some serching, looking at power adapter, I saw only 4,5 for + and 7,8 for -. No other pin used.

So I watched about what pin cnmatrix use to push power and from this doc 24V and 54V PoE Pinout details for cnMatrix EX/TX series switches you can clearly see following:

For all cnMatrix switches, our 2 Pair PoE (2PPoE) delivers 54V following Alt-A (MDI-X) polarity wiring. 2PPoE delivers up to 30W from the PoE port:

1/2 (negative)
3/6 (positive)

This configuration is not good for mikrotik of course.

For our 4PPoE implementation (up to 90W power), we implement the 54V as Alt-A (MDI-X) from the data pairs, and Alt-B from the spare pairs.

1/2 (negative)
3/6 (positive)
4/5 (positive)
7/8 (negative)

neither this configuration is good for Mikrotik because it can’t manage current on 4 wires.

When in Passive 24V mode, we switch off the 54V power on the data/spare pairs, and turn on 24V on the spare pairs following Alt-B.

1/2 (off)
3/6 (off)
4/5 (positive)
7/8 (negative)

this is only compatible configuration with Mikrotik but in case of this CCR is not enough because it consume minimum 33Watt while with that configuration cnmatrix is capable to erogate only 15Watt.

In fact creating an ethernet cable with following wires configuration:

side A => normal standard B colors (white orange, orange, white green, blue, white blue, green, white brown, brown)
side B => white brown, brown, blue, green, white blue, white orange, orange

the Mikrotik powered up on block 2 ports (purple) because with that cable I send current on 1/2 (negative) and 3/6 (positive). The only problem are the data. Obviously it won’t communicate due to a wire inversion.

Teorically it could be possible to use a cable to power up Mikrotik and an SFP 1000BASE-TX port (for example) for data. In that way it work for sure. It’s a workaround at moment.

The best should if Cambium could send almost 40-45 Watt on only 2 wires in 4PPoE implementation using only 4/5 for positive and 7/8 for negative making a software modify.

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