hi,
There is no real fixed protocol on RS485, in principle it is the same as RS232 you send and receive data just like RS232.
RS485 is the way it works electrically, it doesn't say anything about the data being send (or received).
The difference between RS485 and RS232 is that RS232 is bi-directional and RS485 not, in other words with RS485 you must tell the driver chip you want to receive or send data.
With RS232 the communication is between 2 devices, with RS485 many more devices are possible and are connected in parallel with each other.
So RS485 is different in that way you must specify in the data you send to which device you like to talk.
This is because you only want an answer from 1 device (UPS) and not from all the devices, that would be very messy on the RS485 bus.
Modbus is a software protocol that can be used with RS485 but the devices must talk Modbus, that you must check first.
Now i think of it, just check the protocol the devices talk and do some investigation on that protocol.
The hardware part is no problem at all, that are probably only 2 wires connected from device to device.
When you know what protocol is used whitin the devices you must implement the same protocol in your Bascom AVR program.
↧