Can I use SPEBlox Long to implement a 10BASE-T1L system with PoDL/SPoE?

I’m interested in using SPEBlox Long to implement a system where a base node and endpoint node can communicate with each other over a single pair, while allowing the base node to power the endpoint node over the same pair as used for data.

I see SPEBlox Long can achieve the 10BASE-T1L data, but can I also achieve PoDL/SPoE to provide 48V on the wires?

The current implementation of SPEBlox Long does not support the SPoE PD or PSE functionality. That is, the auto-negotiation based protocol where both a PD and PSE auto-negotiate a specific power level. Achieving that requires some extra circuitry that simply isn’t present on SPEBlox Long.

However, it is possible to inject a voltage onto the single pair connection, “on top of” the data lines. Doing this would allow a simple clean DC voltage to be injected on one SPEBlox Long, then extracted on the other SPEBlox Long.

It’s worth mentioning that this is not a typically standard way of achieve PoDL/SPoE, but it is a method used in other literature (like here)

Achieving DC voltage injection on SPEBlox Long requires some soldering and modifications to the board that will void the warranty. It’s not a production ready solution, but it is suitable for a prototype. Also adding a voltage on top of the data lines will reduce the maximum range of SPEBlox Long. Steps on what to do are below.

Step 1: Procure hardware
You will need to order two inductors.

You will also need

  • Fine tipped soldering iron
  • Solder
  • Tweezers

Step 2
Solder the two inductors in the locations shown (L6, L7)

This connects these two inductors, and enables the VBus (the power applied to SPEBlox Long) to be injected onto the single pair lines.

Step 3
Connect both SPEBlox Long together using a single pair ethernet cable.

Step 4
Power on one SPEBlox Long with a 5-60V supply. Let’s call this the PSE. This SPEBlox Long will inject that same power supply onto the single pair lines, and power the other connected SPEBlox Long (let’s call this the PD).
You can extract the received voltage on PD SPEBlox Long by connecting to the Molex PicoBlade power connection on it.

Note that you will see some voltage drop on the single pair lines. Thus if you need 48V at the PD, you might need to experiment to get the right voltage at the PSE; expect a voltage drop of around 1-2V, depending on cable length.

Please note that with this, mileage (literally) may vary. You may only get 200-300 meters range on the data, or possibly less. It depends a lot on the type of cabling and the cleanliness of the DC voltage.

– Copied from customer query –

The supply voltage is 5 to 60vdc. You warn of an absolute max of 65v.

Therefore we assume 48-52 will be OK, no overheating or cooling required?

The 2.2.3 SPE Port terminal.



Is there any polarity between the 2 devices we need to be aware of.

Polarity sensitive?

Short protection?

Yes 48-52V is fine.

You probably won’t need any cooling, the board doesn’t dissipate much power.

For polarity, keep + to + and - to - on both boards. They are short protected.