How can I access the fault signals on SPEBlox Long?

– Copied from customer email –

We were wondering if it is possible to implement Link fault pass-through on the SPEBlox-Long modules. This way our routers can detect easily detect a link loss, which in turn can trigger an alarm output for our PLC. Currently the switch does not detect a link fault on the 10Bae-T connection if the 10Base-T1l connection is disrupted.

If I understand correctly, you’re looking for a way for an external device to sense when the 10BASE-T1L link has been lost on SPEBlox Long

At present this is not possible easily on SPEBlox Long because there are no management or IO signals broken out on the board.

I believe simplest way to do this would be for us to breakout the LED signal that indicates whether a 10BASE-T1L link is present. This would take the form of a simple IO signal which you could interface with your device.

A better way would be for us to breakout the UART port on the microcontroller, and then write some simple monitoring firmware on the onboard microcontroller.

There are test points on SPEBlox Long connected to the UART port that could be used for this, but they’re just solder test points so would not be a robust connection. Also the onboard firmware would need to be modified to output link information for this UART port to actually be useful.

I’ve pushed these suggestions to our development backlog, so I expect we can start to implement these on the next manufacture batch in July 2024.


I am the customer from the email.

We are currently using two PLCs that need to communicate with each other over long distances. The connection is as follows: PLC <10base-T> Switch <10Base-T> SPEBlox Long <10Base-T1L> SPEBlox Long<10Base-T> Switch <10base-T>PLC. The switches have a relay output that can trigger a lost link on a certain port(s). The 10Base-T1L is the most likely link to be broken due to how the hardware is used. Currently, if the 10Base-T1L link is lost the switches we use cannot detect a link lost because the SPEBlox Long 10Base-T connection to the switch is still active. With a link fault pass-through (LFPT) feature the 10Base-T connection is also cut off when the 10Base-T1L is down. If this could be integrated on the SPEBlox Long then the switches we use can detect the lost link and trigger the relay output to the PLC.

Without an LFPT feature, the solution you suggest can be used to notify the PLC directly with the SPBlox Long instead of going through the switch and its fault detection.

Actually this would be super easy to implement in a simple way. We could just have the onboard MCU poll the 10BASE-T1L PHY periodically to check link status. If it detects that the 10BASE-T1L PHY has gone down, we can simply force the 10/100BASE-T PHY to shut down.

That’s likely an afternoon of work and we can issue the firmware update to you. A guide on how to actually upload the firmware is in the link below. You need about $30 of hardware to do it.

Does this sound reasonable? If so I can push this to our software engineer to push out over the next month.

Hello Josh,

Yes, this sounds like an excellent option for us.

P.S. We ordered the appropriate Tag-Connects.

We’ve added it to our development timeline and should expect to roll this out in around 2-3 months.

Hello Josh,

Thank you for the update and timeline.

Would it be possible to en/disable this feature through the UART connection?

Also with the current default software does the device give any output on the UART?

Definitely possible but it may add some time to the development because that means creating a basic UART parser. I will discuss with @aaron when we start on this mini-project later this year.

At present there is no UART output, that might be a nice thing to add too.