Right now i am looking for a better way to communicate to our wired nodes in a project that we are working on.
Currently there is 1 main node that all other nodes talk to that in turn handles all data back to a single computer. The nodes talk to the main node via Full Duplex 485.
I can do 4 nodes this way by having 4 separate 485 drivers sharing the same serial port to provide information to the nodes via the RS-485...
Topology goes as follows:
computer ----> main Node--> rs-485 --> daughter node |--> rs-485 --> daughter node |--> rs-485 --> daughter node |--> rs-485 --> daughter node |--> rs-485 --> daughter node |--> rs-485 --> daughter node
(there are up to 12 nodes at this time that i need to communicate with, but more will eventually be created)
the rs-485 on the main node shares the second serial port on the device that is being used (there are 2 serial ports the other is being sent to the computer).
If i put a 5th device on the port that is live the signal on the serial port at the atmel device gets pulled from ~4.2V to about 2.9-3V for a digital high signal not including any extra noise from the multiple cable runs.
The length of the cables vary from 60Ft to 200Ft.
each node has a dedicated cable run that is terminated at the end of the run.
What is a recommended way of doing the communication between a single main node to many daughter nodes and allowing the daughter nodes to talk to the main node, but not to one another.