Problem (Issue) Statement | A General Guide For RS-485 Communication. | ||||||||||
Description: | A general guide for RS-485 communication networks. | ||||||||||
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Symptom and Finding: | NIL | ||||||||||
Cause: | A general guide for RS-485 networks. | ||||||||||
Solution: | Summary:
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The best way to ensure a robust and reliable RS-485 network is to build it around a daisy chain configuration. |
Cable Distance:
Step 1: RS-485 standards allow communications of up to a maximum of 1km cable length for a network segment. This length is the total cable length between the first controller in the network and the last controller in the network. It is not the length between one controller to the next successive controller. Refer to the following picture for further information
Figure 3: 1km Maximum Cable Length Requirement Between First and Last Controller in the Network
Cable Type:
Step 1: RS-485 specification recommends shielded twisted pair cable to reduce two major sources of problems for external noise: radiated EMI and received EMI.
Step 2: The recommended cable specifications are as follows:
Example of the shielded twisted pair cable:
Figure 4: Shielded Twisted Pair Cable Illustration
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Common Issue
- Hardware devices connected using star topology, which resulted in hardware status down.
- Project deployment using incorrect cable type, noise induced by the environment can also cause hardware status to be down.
Date Documentation:
5/11/2018 (Rev 1.0)
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