Temporary solutions for RS-232, RS-485, and RS-422 cabling

RS-232, RS-485, RS-422 in the field debugging often encounter a variety of serial communication problems, such as RS-232, RS-485, RS-422, different ports of communication connection problem, usually between RS-485 and RS-422 conversion is very convenient. But when the RS-232 port and the RS-422 port communication, the site no other conversion mode, if the mail may wait for a long time. There is now a temporary solution. (1). RS-232 and RS-422 RS-422 R +, T + transient, and RS-232 Gnd connected. RS-422 R-and txd RS-232 is connected, RS-422 T-and RS-232 rxd can be connected .. The principle is as follows: the electrical characteristic of RS-232-C interface is that the voltage is negative logical relationship. That is, the series "1",-5--15 V; logic "0" + 5-+ 15 V. The noise tolerance is 2 v. That is, the receiver is required to recognize signals as low as + 3 V as the logic "0", and signals as high as-3 V as the logic "1 ". Electrical Properties of RS-485: The logic "1" is expressed by the voltage difference between two wires as + (2-6) V; the logical "0" is represented by the voltage difference between two wires-(2-6) v. So when the RS-232 sends "1", the voltage difference between txd And Gnd is-3--15 V, the logical "1" level is formed between the R + and R-of the RS-422 (Note: The line level attenuation is small ). When the RS-422 sends "1", the level of the logical "1" formed between T + and T-of the RS-422 is + (2-6) V, the logical "1" level is formed between txd And Gnd of the RS-232 (Note: Because the RS-422 Communication adopts the differential level, the long attenuation of the line is also small, the RS-232 receives a level that is basically maintained at 5 volts ). Communication distance can be considered to be based on the RS-232. That is, generally less than 50 meters. I tested it on a temporary basis in POTA Petrochemical, and it was okay after 40 meters.

(2) The RS-232 and RS-485 RS-485 R +, T + transient, and RS-232 Gnd connected. RS-485 R-, T-transient, RS-232 rxd, txd transient, the two can be connected. From the RS-232 is full duplex, The RS-485 is half duplex, if you want to communicate, you need to do the processing in the communication program, but temporary use (such as the power meter connected to the NAS-968D/e, use DEBUG to set the address of the power level table ). After preparing the number, first press the Power Meter button 2 and send it once (due to the short sending interval) and stop. You can see that the second string received is Address Setting confirmation. (In this case, rxd of RS-232 cannot be connected, but the address setting confirmation string cannot be seen ). The above is a little experience for me. If not, please advise.