TX4 non reversible Data USB socket

Thank you to all at OEM who have been working on this marathon 3 phase project. Much appreciated by yours truly, as I am involved in a fresh 37kWp system on the roof of my church in London W13.

System installation has gone pretty smoothly, and the emonBase / emonTx4 / emonVS (no plug) monitoring solution was brought up over the weekend. 3x100A CTs in the feed from supply meter to “big switch” main breaker, plus 3x50A CTs in the feed from PV inverter to its MCB on the generation distribution board. I fully agree with the 1,2,3,1,2,3,… order rather than 1,1,2,2,3,3,…

I bought the emon hardware a few weeks ago, before I was aware of this thread, and was fully expecting (dreading) the download / build / program firmware procwss. Imagine my joy when I found that Trystan had me covered, and it was all going to be sweet and easy.

And it largely was sweet and easy - the things that caught me out were my own fault. I am really confused about this non-reversible USB-C socket on the the emonTx4. My three boxes are right next to each other, so I wanted a wired connection.

Trying to follow instructions, I did the full update - after failing initially to find the local emoncms Admin tab. It was off the bottom of my local 1280x1024 monitor, and I needed to click in the right place then scroll down to find it. Doh!

On connecting the TX4 to its Base using a USB-A to USB-C cable I found only ttyAMA0 and ttyS0 listed in the Update Firmware section dropdown. Knowing that these tty lists are somewhat flaky, I tried both, without success. They went through 10 tries each, and a red LED inside the TX4 flashed each try, so I assumed at a hardware level communication was successful.

After a pause, I thought I’d try again with the USB-C plug in the other way (sadly diverting the previously nice short cable lay between Base and TX4). Initially only the same list of devices in the dropdown, and the same LED flash at each unsuccessful try. But at some point ttyUSB0 appeared as a third option, and all became good.

So as a good hardware engineer I sought out the pcb details, and found the TX4’s schematic and pcb layout. Indeed the A & B side power pins on the USB-C socket are connected so it will work either way round. But the DP and DN pins are only connected to the one side and not the other. None of the other pins appear to be wired.

It’s hardly a trial to have to live with a less well routed and dressed cable, but I would dearly love to know why reversibility of power AND non-reversibility of data were explicitly chosen. I am sure I will not be the last person to trip over this.

Now awaiting the opportunity to visit my new hardware again, and install Dataplicity on it so I can continue remotely to build out the monitoring. More questions will doubtless ensue :slightly_smiling_face:

And I’m sure you’re right there - until the next p.c.b. revision, when I’m told the USB-C plug will be truly reversible.

Also pointed out for improvement is the reliance only on the connector to support the c.t. extender board against the insertion force of the c.t. jack plugs.

I moved this to a new topic as not strictly part of the original thread.