RS485 or LAN/WiFi connection?
Posted by      02/01/2019 17:37:11     Railduino 2.0

PROS AND CONS

Every type of communication has its advantages and disadvantages

RS485

PROS: reliability (low number and hierarchy of communication devices) and security (enclosed bus)

CONS: slower communication speeds, limited range

LAN

PROS: high communication speed, unlimited reach

CONS: higher level of complexity (large number of devices in the LAN) and communication security


LOXONE

Let's consider an example when we want to switch on the light by pressing the button - the button is pushed and the signal is led to the dig. input of the Railduino module, while the light is controlled by the Railduino module's relay output.

The entire process of transferring information from the Railduino module to the e.g. Loxone and back can be written as follows


1. Processing the Railduino module request (push button) and sending the status to Loxone (UDP packet):

LAN - max. 20ms

RS485 - max. 30ms
2. Processing on the Loxone side (receiving information and performing the next steps) and sending the command to the Railduino module

LAN - max. 25ms

RS485 - max. 35ms
3. Running the command by Railduino (lighting up)

LAN - max. 20ms

RS485 - max.30ms


So for this case, the response time (and whether the RS485 or LAN is used) is max. 95ms.

Therefore, the delay is minimal. Greater effect on the delay between the push of a button and the lighting of the light will have, for example, the delay of the current source for the LED light itself to be powered on.


ESTIMATION OF BUS SPEEDS

LAN

- 10/100Mbit

- tens of microseconds

- lower probability of bus collisions (UDP protocol)

RS485

- 115200 Bd

- units of miliseconds

- greater probability of collisions on the bus (UDP protocol)


CONCLUSION

Whether to choose an RS485 or LAN connection is purely a matter of considering all Pros and Cons mentioned in the first paragraph.