https://ncedcc.zendesk.com/hc/en-us/articles/200933425-Common-Cab-Questions 

• The NCE PowerCab / DCC Twin can only use cab bus addresses up to 10.
• 0-1 are the internal twin cabs.
• 2-7 are for throttles.
• 8-9-10 are for cab devices.
• The NCE AIU01 can use only cab bus address 4 or 48-63. That means effectively on a PowerCab bus it can only use address 4, there can't be more than one on the whole bus. Quite disappointing but OK enough for home since I had no plan to have more.

I’ll repeat this in case it’s useful for others:

• On an NCE PowerCab or NCE DCC Twin command station, only one NCE AIU01 board is supported and at only cab bus address 4.

Regarding the NCE cab bus and the NCE USB interface, I realized I have two of them at home (one straight, and one modified for the direct serial-to-Arduino). They are both on address 63. I just realized the other day they were on the same address and it’s somehow not a problem, although only one polls the NCE AIU, the other one just sends commands.

On the NCE Power Pro: highly recommended to ditch USB and use the RS232, otherwise will have limited functionality ⇒ it was OK for pure cab command as I was doing before at Randall but all indications say it is not suitable to get the AIU stuff. Oddly enough, AIU status works with the Twin but the pages all say it will probably not work with the higher end Power Pro.

Update: Tried it with the Power Pro and I can confirm.

• The PowerCab / Twin can query one NCE AIU. I connect JMRI to the cab bus via an NCE USB interface and I can read the NCE IAU status. The refresh rate is appalling but it works.
• I plug the same NCE AIU on a Power Pro, and the same NCE USB on the cab bus of the Power Pro. JMRI cannot read the data back from the AIU.
• I plug the same NCE AIU on a Power Pro and this time use an USB-to-RS232 adapter on the computer. JMRI can now read the data back from the AIU.

Of course, now I remember that I read about this a while ago:

https://sites.google.com/site/markgurries/home/nce-info/nce-usb-limitations

Bottom line for Randall I'm going to have to switch to RS232 with a USB adapter.

All forums and sites point to the same Keyspan USA-19HS adapter: http://amzn.to/2dBYkNY  … $25

Cable: Straight (not null modem) RS232 cable. 50 ft one http://amzn.to/2zn4vfl … $8 from monoprice.

RS232 max length is 50 feet. That cable worked fine for me.

If the AIU had turned to be a dead end, the fallback plan B would have been to get an arduino with a wifi or ethernet shield, wire sensors directly to it and have a Go program generate NCE AIU status like at home. This is similar to the Translate project where I have a local program on the computer that simulates an NCE bus protocol and JMRI just thinks it’s connected to some NCE thingy over ethernet. Works like a charm.