Computer Interfacing
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Does DB9-RJ45 Adapter Require A Driver?

Accessing intelligent controller with optional RS232 interface.


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Author Message

Jun 27, 2012 1:21 pm

I don't think I will get an answer within this week as it is very urgent. I think it will be the other way round ---- I will find out myself and let you know.

Anyway, 1/1000 chances are somebody will reply within this week.

I am trying to controlling an lighting intelligent controller with DB9 as the PC-end and RJ45 as the controller-end. It is understood that by sending a series of bytes (maybe low significant byte
s for bulb and high significant byte for on/off,etc) to the COM port, the machine just works by turning on or off the light (assignable up to 10 bulbs) and better yet, control the brightness of the bulb.

The problem is, even with the manufacturer's program (I suppose it was written in VC++) and DB9-RJ45 adapter supposedly from the manufacturer with the Chinese-made intelligent controller itself still won't work. So how do I suppose to write the coding myself to communicate with that controller?

I checked the adapter wiring, performed loopback test, used a wide variety of serial port library and standalone program, and finally ended up with my own Turbo Pascal 7 with a reference sheet on serial port (control / status) registers.

So here's my questions: (Sorry for my lousy English and unchecked spelling, if any)
1) Why do Pascal and Assembler in DOS mode under Windows 7 32-bit always ended up with 5 data bits on exit although bit 0 and 1 in the Line Control Register are all set to 1? And why does Windows reporting Pascal is accessing COM2 while 2F8 (default is 3F8) is already set as the COM port in the BIOS settings (Windows detected COM1 as 2F8 correctly)? "MODE COM" DOS command is OK.
2) Does conversion from RS232 signals to RJ45 connector require a driver? A quick check on DB9-RJ45-DB9 loopback test shows that Tx is redirected correctly to Rx.
3) The supposedly original DB9-RJ45 wiring (done with continuity check on each output pin) shows that 4 lines are used: Rx, Tx, Sg (Signal Ground) and the other one uncertain (because of mess of information about the pinout on the Internet before reaching this Web site), which I guess is DCD (Data Carrier Detect). My question is, what would the communication protocol be if only Receive-Transmit and a Carrier Detect (not quite sure what purpose it serves, too) involved?

Last but not least, Serial Port is whole lot difficult to program than Parallel Port.
And yes, the baud rate on the intelligent controller is 9600 and matches with that of my program, of course.

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