hi

I have a device that has a communication port but I do not know which type of connection. I've measured the voltages on pins. The following values were obtained:
http://upload7.ir/imgs/2014-11/32169635398783941206.jpg

in your opinion, this is which connection (rs422, rs232, cmos, etc.)? how can determine type connection?
in The manufacturer's catalog Been picture following:
http://upload7.ir/imgs/2014-11/46766234832118096618.jpg

Also come in the catalog the following descriptions:
http://upload7.ir/imgs/2014-11/67986308574740762920.jpg

 

If the device needs to run a protocol, like sending some control character or a couple ASCII characters to start a transmission, you're stuck because you have no idea what the protocol is. If you just want to see if it's spitting out data, like a printer output, then read the text in the 3rd image you posted.

The 3rd link/image tells you, "connect the serial communication port of the device you are using to the local RS232 MIL connection serial port of the AquaMaster unit or hard wire into the RS424 terminals provided within the terminal enclosure. If using PC or laptop, then any standard communications package can be used: Window Hyper Terminal, PC Tools that transmits as a dumb terminal.

I don't know what RS-424 is. I suspect it is a typo error, and should be RS422, a differential mode serial spec for longer distances than RS-232. So the device is either 232, 423 (rare) or 422.

RS-232 operates over a wider voltage range than RS-422 so a PC with an RS-232 port (or USB/232 converter) won't be damaged by an RS-422 signal.

Connect a PC with a 232 serial port and run a terminal program to see if the port is spitting out data.

Try one of the voltage pins to Rx on the PC port (with a ground to ground). If that doesn't work, try the other pin to Rx on the PC port.

The lower differential range of a 422 output might not trigger bit recognition but it won't hurt anything. If the device port is 232 (highly likely) and the device is in constant send/transmit mode, then you should see characters in the terminal program when you get the right pin on the Rx terminal (and ground).

You'll have to mess with word size and baud rate and parity and all that to make sense out it.

Why aren't you looking to replace whatever this dinosaur is with something newer?

 

> <i>If the device needs to run a protocol, like sending some control character or a couple ASCII characters to start a
> transmission, you're stuck because you have no idea what the protocol is.</i>

It works like this.

I hardly found a transducer from the manufacturer and find rx and tx and gnd by it.

I get below voltage in run time on each pin (by multi meter):
top and bottom pin are nearly 3.5 volt and Remain at the same level when pc and device exchange data together.

left pin become nearly -4.92 volt in connect time and change when pc and device exchange data together (for example become -0.8 or -2.3 or -3.2 and then return to -4.92 when pc and device do not exchange data together )

so I think Connection is RS232. As you guessed

> <i>Connect a PC with a 232 serial port and run a terminal program to see if the port is spitting out data. </i>

but I use opto-isolated RS232 for this work as following link:
http://www.kmitl.ac.th/~kswichit/Rs232_web/Rs232.html

As you can see, this circuit is for ttl to RS232. so i use max232 for convert ttl to rs232 but this circuit don't work! why?

> <i>You'll have to mess with word size and baud rate and parity and all that to make sense out it. </i>

i have this values

> <i>Why aren't you looking to replace whatever this dinosaur is with something newer?</i>

i have many of this device and it is expensive For me to replace with something newer