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RS232/RS485 Serial Tech. PC Interface with other Module

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rs485 adapter schematic

Hi,

I would to use RS485 for my interfacing between PC and few other serial module.

What's the step should i start on the Hardware and Firmware(Protocol) side?
Example I had 3 node (node1=PC, node2=MCU1, node3=MCU2).
My PC only had one serial RS232 port, and the MCU also only had one serial. If i would like to use standard RS232 for all the node in interface, so i just have to put a RS485-RS232 convertor?
As i know the basic RS485 circuitry is show bellow.

Thank You.
 

blueroomelectronics

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rs485 pc interface

Be careful, Windows does not toggle RTS (required for switching /RE & DE on the MAX485) properly and the circuit may not function.
www.RS485.com posts dozens of working RS485 adapters with schematics.
 

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pc,interface,rs-485,vers

Hi,

Thank for your remind. I have few question.
- According the MAX485 Table Function, in what condition we should set the /RE=1 and DE=0?

- May i know RS232 can be connect many nodes in serial bus as Serial BUS Diagram shown. If yes, what's the different between RS232 and RS485 advantage and disadvantage, ex: data transfer speed, limited node, limited length and so on..

- If the design is interface with the PC. Is it all the node on the serial bus (no matter RS232 or RS485) will be the Slave always in the listening mode?

Thank You
 

blueroomelectronics

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pc rs485 interface

Most designs tie the RE / DE pins tog,ether.
If you can work with SOIC ICs the FT232RL datasheet has the instructions for a simple USB to RS485 adapter. Very nice.

RS485 is half duplex, only one device can have the bus at a time. RS422 is full duplex but only 10 nodes. Actually RS422 is very easy to convert to RS232 (don't need the RE/DE stuff)
 

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rs485 module

Hi,
blueroomelectronics said:
Most designs tie the RE / DE pins tog,ether.
If you can work with SOIC ICs the FT232RL datasheet has the instructions for a simple USB to RS485 adapter. Very nice.
I think this is the option for me to do convertion. May i know, can the hyperterminal interface with USB device?

blueroomelectronics said:
RS485 is half duplex, only one device can have the bus at a time. RS422 is full duplex but only 10 nodes. Actually RS422 is very easy to convert to RS232 (don't need the RE/DE stuff)
Can you please guide me how to use RS422? Do you have any application note and so on.

Thank You.
 

blueroomelectronics

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usb to rs485 half/full duplex

The FT232R will appear to be a serial port to windows, just install the free driver from their site.
They also have the schematic for an RS422 version in the datasheet.
 

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