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發表於 2014-9-30 11:47:08
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Isammy大你好,
你提到 RS232=>RS485 功能就正常~雙邊都不行。
理論上你如果單向可以的話,理應信號轉換應該是行的通的。
你的問題應該是在信號轉換的電源問題吧~
就如同你說的, RS232->RS485 是可以正常工作,信號轉換的電源是由 RS232 port 所提供(無源)。
你的問題可能為:
1. 另一邊 ( 應該是 device 端,可以正常猜測為電腦端) 的 RS232 並沒有提供電源(透過 DSR/DTR供電)。
2. 信號衰減,RS232提供的電流不足(純 I/O腳)
網路資料,提供給你參考:
http://www.rs232-to-rs485.com/
How to choose the right RS232 to RS485 converter.
When shopping for a RS232 to RS485 converter you should first determine if you need an industrial strength or a commercial/consumer grade converter, this depends on which environment you plan to use the converter. Next you should determine if you need and isolated or non-isolated converter, where after you can decide if you need an externally powered converter or if you can use a port-powered converter. Next you can find the connector type you need, either DB9 or DB25 connectors, terminal screw header, RJ11 connector or a combination hereof. Finally you should decide if you want LED lights for the TX/RX lines, this can be very helpful when troubleshooting.
What is called 'Automatic Send Data Control', which controls the data flow, is strongly recommended for most applications and devices, this feature is built into most modern RS232 to RS485 converters.
The short check list looks like this:
1. Industrial or consumer grade.
2. Isolated or non-isolated.
3. Externally powered converter or if you can use a port-powered.
4. Connector type.
5. LED lights.
或你可以參考duke83的建議,直接改用 RS422,不過如果你的問題是另一邊 port powered 有狀況的話,也是無效的。
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