RS-485 and CSMA/CD

[yuzhaitongzi]

How to implement multi-master RS485 bus for carrier monitoring multipoint access/collision detection in hardware design?In the circuit design of the rs485 bus, I want to realize what the tx is thrown on the bus when sending, and what rx can receive from the bus.And I found an article that seems to be possible, but I do not know how to design the circuit, and whether these logic circuits have and integrated chips can be used.Below is a link to the reference article:https://www.cnblogs.com/amxiang/p/16254143.html
thank you very much!!

 

[KlausST]

Hi,

you posted a guessing game....

What is "carrier monitoring"? .... when speaking about RS485.
The link leads to a foreign language. Edaboard is English only.

You give no informations about baud rate, number of masters, number of slaves, power supply voltage, bus structure, length and so on.
You give no information about your idea, the expected function / working principle of the circuit(s).

The second schematic (in my opinion) makes no sense. An optocoupler is an "isolating device" .. but in the circuit the "isolating" feature is disabled.
And there is no single value in this circuit.

What do you expect us to do?

Klaus

 

[FvM]

RS-485 has no hardware collision monitoring feature, in contrast e.g. to I2C or CAN. Conflicting simultaneously enabled drivers don't result in a defined state, can be either H, L, or in between.

A bus device may compare received with transmitted RS-485 data to verify successful transmission. But seeing correct data at the transmitter bus interface doesn't guarantee that's also correct at the other bus end if another transmitter of unknown strength drives against the first transmitter.