I am normally a cable it first person and leave wifi/wireless for things that need it, only so much spectrum. but the amount of data from an RFID reader will be that small even at slow speeds it should be fine.
The level of security and performance is something that you should define, as that would help select the best method; or at least ensure you have thought about things.
e.g.
- Someone could turn off you access point… maybe, but they could also turn off a switch… so I dont see that as a real issue here.
- Someone could “signal jam” the wifi; yeah, but they could also cut your cables.
and so on…
My thought is given that you are not likly to secure the cables inside the walls etc, then there is already risk; this risk may not be of any real concern.
e.g. HID Signo readers are not cheap and have lots of things to help secure them. But in the current firmware, any attempt tp connect to it with bluetooth (as it supports bluetooth/phone tokens) results in the reader not responding to anything else. So you place a bluetooth connection box nearby, but hidden and the door will no longer open for anyone… most securty people then leave the door unlocked to allow staff to come and go as needed… security defeated…
key point of the little story, every install will have its pros/cons.
I liked the networked/wifi idea simply because:
a) no cables to run, just need power
b) anti-collision is already taken care of (udp/tcp level)
If you are to run a bus like RS485 then you need to consider how to manage the back and forth between reader and central server. the simplest is the central server will poll each reader and wait until either it gets a valid response or a timeout. this can then lead to some delays if too many readers are on the one bus especially if one or more readers go off line as they will spend the max amount of time at those readers polling timeslot. To address this you would consider more runs with less nodes per run… with a fast enough device at the central location running a hand full of RS485 adapters and poling each in threads would work well.
If they are worried about security, then you can add your own layers as needed.
e.g. You could give every reader/esp32 its own AES key and encrypted the data at the “reader level” then even if someone gets onto your PSK wifi AP, they still cant read/create their own packets as the server should fail is packet checks post decryption.
If someone hacking the wifi is an issue, just keep in mind "what’s stopping them plugging a cable into you RS485 bus, or an ethernet port etc.
Key Point: Security needs to be proportional to the need.
