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tashinz

DTR signal on SCU41

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I have some EXTECH programmable power supply which I need to communicate to through RS232 port on CJ1W-SCU41. Now, the pinout of RS232 port on Extech is given only by connection to PC: Extech PC pin 2 ------ pin 2 RX pin 3 ------ pin 3 TX pin 4 ------ pin 4 DTR pin 5 ------ pin 5 GND so, I made a cable for connection to port 2 on SCU41 like: Extech SCU41 pin 2 ------ pin 3 RD pin 3 ------ pin 2 SD pin 4 ------ pin 8 DTR pin 5 ------ pin 9 SG When i send messages from terminal program in PC, it doesn't work until i enable the DTR in PC port setup (from terminal program). Messages are simple, ASCII, like: V?<CR> from terminal program, and the answer is also simple: V 40.000 00.000 CV Now, when I program that in protocol macro it doesn't work. in trace, i see it sends V?<CR> but the lines DTR and DSR are flat. Is there any way to turn on DTR on RS232 port on SCU41 like I did it on PC? also when send messages from PLC using PMCR function it sends error flag 1794.10 (so scu is unit 11). Anyone knows how can I set this DTR on SCU41 port2?

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Try hooking RTS from SCU41 to DTR on Extech.

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you mean to wire the SCU41 RTS to DTR on Extech? Will try it, but what is the meaning of the DTR pin8 on the SCU41 port2? thanx for the response, i will try it tomorrow morning. Edit: well, the fact is i don't know where is DTR on Extech. I don't have pinout, in manual only the scheme from my first post is given. looking at status bits in word n+17 (in my case it is CIO 1792, you can see in manual) bit 7 is DTR signal is High. when i trigger the pmcr this bit turns ON and after exec flag turns off it turns off tool. but the bit 3 - RTS signal High remains 1. i tried to use message in protocol macro with open command, then this bit 7 remains 1 allways. I am not sure what to do more. Edited by tashinz

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DTR = Data Terminal Ready. RTS = Ready To Send.

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I think that your original wiring may be correct. I have filled in what we suspect the labels on the Extech would be. Extech SCU41 SD pin 2 ------ pin 3 RD RD pin 3 ------ pin 2 SD DSR pin 4 ------ pin 8 DTR SG pin 5 ------ pin 9 SG Try adding a jumper betwen 4 and 5 on the PLC (RTS / CTS). |-- pin 4 RTS | |-- pin 5 CTS Edited by PMCR

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well PMCR I did what you said, nothing happens. The settings of the RS232 port on Extech acording to manual are 9600, 8, 1, None, so I set up the SCU port that way. I played with CTS enable on port settings, no difference, also wiht full or half duplex, nothing (RS232 should be full duplex though). One thing i tried, since from terminal program Extech replies, i connected pc with scu41 port2 with regular programming cable i use for plc programming, to see what message pc's terminal program sends. i started trace in protocol macro and i saw that the message from terminal program has CR+LF (0D 0A) in the end although in manual there is only CR. so i have changed it, but nothing happens. on more thing. when extech recives message from terminal program it beeps even the DTR is disable but there is no reply. if i send some non-existent message it doesn't beep. When I send correct message from scu it doesn't beep. this leads me to conclude that wiring is wrong or correct message from protocol macro (simple as V?) is changed somehow. I am loosing ideas. Edited by tashinz

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Can you do some traces in CX Protocol and post? I have looked at some Extech manuals, and I agree that it looks like what you are doing is correct. You could also try a 50 ms send wait on the send step to let the DTR line come on early. Probably will not help, but worth a try. The 1794.10 bit that turns on is the 'abort complete', which basically means that the sequence completed abnormally, and typically means there was a timeout or a receive match.

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I've posted the protocol macro project (as zip didn't alow me to upload the psw) and cx-programmer (only the pmcr part). my colleague told that this is half-duplex altough i have read that RS232 is full duplex. so i tried both. also i have played with modem control of the communication sequence, still nothing. i have also e-mailed extech tech support, out of desperation. 1.pic is half duplex modem enabled 2. pic is full duplex modem enabled 3. pic is half duplex modem disabled and 4. pic is full duplex modem disabled. CommExtech.cxp CommExtech.zip Edited by tashinz

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You are rapidly approaching the end of things that you can try on the Omron side. You have tried all the combinations that I would have done. Is Extech able to help understand the use of the DTR signal on the power supply?

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Well, I employed some of my colleagues here. Here is what we found out: 1. on my toshiba tecra laptop i have one physical serial port. tried to send messages from terminal program no responds from extech. i tried that from virtual port, using usb to serial converter, no responds from extech. tried that with other laptops with usb to serial converter (they don't have physical) no responds from extech. 2. tried from a regular pc, extech replies. I've used the same cable, one got with extect (i.e. null modem cable). 3. then we start to measure voltage on signal cables. found out that voltage when connected to laptop's physical serial port is 8V between DTR and SG (4 and 5 pins). when sending messages from regular pc the voltage is 12V. in the moment of sending, voltage briefly falls, since we have analogue voltmeter it is detected very shortly. any ideas?

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well, i think this is the problem, voltage level of DTR. from PC is 12V which is actually a standard for RS232, but from usb to serial converter it is 5V which, of course, makes sense since on the usb there is only 5V. we tried with some usb to serial converter with its own power supply, we got 7V (would this had worked i would have used cx-supervisor to issue commands to extech and then to write to plc). um, any serial device should be compatible with lower voltages that 12V, but not the extech. any recommendation for some voltage level adjuster (don't know how to call it) which would be connected on one side to scu port2 and on the other side to extech providing it with 12V on DTR? in this electrical cabinet i already have omron 220VAC/12VDC power supply. Edited by tashinz

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