Can we cover the wirelles again?
I have a system which communicates with several small units all using μCs.
I want to change the cables and use wirelles. Can you give me a rugh plan of the wirelless system? In blocks and main chips I have to use?
Thanks
D.
In fact the system's topology would lead to this option: there's one master and 4-5 peripherals. The peripherals only reports an event from time to time (the push of a button, per example), thus I don't see the master querying the slaves all the time.
How about serial over RS485 using RJ14 or RJ45 modular connectors? RS485 is a relatively noise immune long distance half-duplex topology and you could even include power on the connectors to power the slave devices.
I'd vote for a RS-485 line. I made something similar for communication among 3 (up to 12) units under noisy conditions.
I used PIC MCUs with MAX481 transceivers.
There is no problem with transmission if you are njt going to power these 5 system from same line . If it is - rs485 wont be your choice - go for X10 over power line or something similar and simple.
Yet your requirements are not clear enoguh - is this master slave or independent nodes . If latter - will need bus arbitrer based or token ring alike or random access with collision handling algorithms (X10 does allow that) protocols.
The company I used to work for had some small bar code reader terminals installed in the Labs and connected in an RS485 'star' to a multi-port 'master' controller. They worked fine. Distance from the 'master' was probably about 80 meters. I suspect each of the terminals had RS485 termination.
I ment - if you have few devices with rs485 interface and need to power them from one place - you will need at least 4 wires not 2 (according to requirements in first post), but that is only for case if you dont have power a location of each device .
Yet it is preferred to have common ground connection between rs485 devices - that means 3 wires.