You said you would collect parking data every 10s, but the battery powered sensor only wakes up every 10 minutes.
I only had the time to read over one sheet from the "Wow" guys.
The "Wow!" guys was the comprehensive solution, They had all the parts and knew how to use them. The other ones were an attempt to build based on "generic parts" that may have other specific purposes. e.f. take a number, Display PIN codes, Remote display, parking display
Early on, I mentioned
BCD (or digital), RS-485, Modbus and Ethernet
They are not in the same category at all:
The BCD I was thinking of was 8 bits, 2 digits, build your own. Not digit select, load digit, display digit; BCD to seven segment decoders also can display FuLL using 7-segments. There's another matrix that can actually do alphanumeric. There is also 5x7 and 5x9 matrices too (i.e. Dot matrix printer). With this method, it's likely no programmable control of brightness
I introduced the RS-485 Adam module to get from digital to RS-485
RS-485 is a multi-drop for 32 devices master/slave serial, wiring scheme; so a little bit of protocal is involved. Serial, is a one to one ASCII data. RS-485 is slow, but can do long distances because the signals are differential. Rs232 works when the devices are close. Everybody messes up RS-232. Levels used to be -3 to -25 V and 3 to 25 V and a whole bunch of signals to control a Bel 103 Modem.
MODBUS takes RS-485 to another level. Lt has a protocal of sorts attached to it. There is also a full and half duplex version, I think. The talk about coils or relay coils. Those are digital I/O. I don;t know a lot about MODBUS and I only worked on two RS-485 things. So, I think everyone (MODBUS) knows what integers are, floats are, digital I/O is. Super simple explanation, Put the 8 bit integer 128 in memory location 3000 on device 32. At least that;s how I understand how it was in its infancy. PLC's (Programmable Logic Controllers) generally support it.
We can say MODBUS runs on Ethernet and so does serial. Serial is packaged under Telnet, so I can go serial-telnet-serial if I wanted using a black box.
Can you imagine an IP address for every parking space. Nope. So, lets have an IP address for every 32 parking spaces. RS485/Modbus will manage those 32 devices. That's your radio receiver that has to pick up the parking sensors. As you said, directionally beam formed fo the greatest coverage.
RS485 can be both home run based or daisy chained. In daisy chain, there are terminator resistors at each end.
The advantage of a hub is easier to troubleshoot. This isn't well known.
The sensors are under the car, surface mounted and battery powered. The sensor supposedly has presence, probably low battery, and temperature minimum. It could have an ESN. It probably doen't have L3-10; or L3 space #10.
Back to some other things, there is telnet and reverse telnet. Computer speaks telnet and a box at the other end might have 1-8 serial ports. they could be RS485 or RS232
So, we can take these RS485 segments in our garage. Maybe a ceiling mount would do some of the floor above too.
Ethernet tends to isolate somewhat the segments because of a transformer in each transceiver so long distance ground loops are non-existant.
24 VDC is a very typical Process control power voltage, so the Wow people put all of the power as low voltage and aggregated it.
A comment about Ethernet. POE switches are expensive, but high power is available. You can get up to 90W with current standards.
https://www.linear.com/product/LT4275
I have POE at home and it can get messy. I have one device, my DSL modem that runs off of POE. The UPS runs my server and network. Power glitches are not 100% recoverable without a reset unless the UPS is in place. The UPS takes care of server too. The UPS in theory can shut down the server gracefully.
So, out of the blue, I knew about this:
https://www.digi.com/products/serial-servers/serial-device-servers/portservertsmei#specifications
https://www.digi.com/products/serial-servers/serial-device-servers/portservertsmei#specifications
One of the 5 digit displays said it doesn't support low voltage power only 120 V. Power is a real pain.
That one early company *take-a-ticket* didn't really have a way to utilize their display for another purpose.
It did offer WIFI control of a specific function. PIN numbers. I don't even know what that is. Control is by the web and therefore I THINK it's possible to control problematically via something like curl or get/put. Missing is a decent IP rating and brightness control.
For a DIY thing, the Wow company did the meat in a PLC or even SBC (Single Board Computer) When you start logging or doing accounting, thats the job for the PC.
Here's
https://spothero.com/philadelphia/downtown-parking a neat parking app. A display of free and handicapped spots in the front of the garage could be useful. e.g.
SPOTS
**********100
HP*********6 (Use the handicapped symbol)
EV Ports***10
Providing Zoning OK with it.