PC-CAB versus MO-CAB

[John_Ess]

I wonder if there is anything - other then 19,600bps speed restriction - that prevents EASY-PC-CAB to be used as a direct replacement of EASY-MO-CAB cable for serial communication?

During programming we use EASY-PC-CAB to exchange data between easySoft and Easy800 module without any restrictions as long as the PC is capable to establish a communication with Easy800 via its RS-232 port.
 
And it is a bi-directional serial communication via RS-232 connection to and from Personal computer (PC) that in this case acts as a sophisticated terminal.

However, Moeller recommends to use another "modem" cable designated EASY-MO-CAB for serial communication between Easy800 and modems, serial printers and terminals.

Why is it NOT recommended to use the EASY-PC-CAB instead, or at least to try it before buying a so called "modem" cable?

My question is: what causes such a restriction?

Cannot we just use the same EASY-PC-CAB "programming" cable for low speed (up to 19,200 bps) serial data exchange with modems, Hyperterminal or any other serial devices?


Best regards,

John

[Maikky]

Dear John_Ess.

I assume Moeller is proposing to use the EASY-MO-CAB because it is delivered with male and female connectors, cables may be connected acc. to your requirements and usable for printers, modems, PC-connection and so on.

We have some small experience with connection of EASY8xx to HyperTerminal running on a PC. It is used for a very low level data logging during test runs. In the beginning we tried to figure out the possibilities and found out, that the use of PC-CAB didn't work. It is possible to get a connection but HyperTerminal is not receiving any data. We never digged deep enough to find the reason. The MO-CAB however was working fine.

We are now using the USB-CAB for "programming" and "terminal connection" because the connection to Laptops is easier and it is working properly for both tasks.

Regards Maikky

[KressSwiss]

Hi John
In addiction to the cable you may realice different baud rates.
- easy800-PC-CAB       max. 19200
- easy800-USB-CAB     max. 57600
- easy800-MO-CAB      max. 57600

More information about EASY-MO-CAB employ this link: 
ftp://ftp.moeller.net/DOCUMENTATION/AWA_INSTRUCTIONS/23450207.pdf

Regards
Hermann

[John_Ess]

Maikky,

Thank you for your detailed description of what might be a good start to further investigate the possibility of using plain easy-PC-CAB with serial devices.

I wonder if anybody from Moeller technical department can share their opinion on this subject as well.

Anybody from Moeller? 

Regards,
John

p.s. KressSwiss is right about lower speed but in this case it is rather irrelevant 

[Maikky]

Dear John.

Just for my information. Why do you intend to use the PC-CAB instead of MO-CAB or USB-CAB?

If there are solutions, which are working properly, why not choose them.

Regards  Maikky

[John_Ess]

Dear John.

Just for my information. Why do you intend to use the PC-CAB instead of MO-CAB or USB-CAB?

If there are solutions, which are working properly, why not choose them.

Regards  Maikky

Convenience, cost and availability. You cannot beat the price of something that you already have to have to work with easy relays. Here where I live nobody even heard about "modem" easy-MO-CAB 
However, everybody who uses easy800 has at least 1 programming (aka. easy800-PC-CAB) cable. So for testing serial communication in range from 9600 bps to 19,2kbps it's convenient to use just the existing easy-PC-CAB.

To Werner / Forum moderators:

Are there any Moeller technical support people able to answer this question or this forum is never visited by Moeller's folks and is made of end-users only?
I'd be glad to discuss this subject with somebody from Moeller as well.

Regards,
John

[befu]

Hi John,

the easy800-PC-CAB needs an additional power supply for the inbuild opto couplers, which will be given by setting the control lines CTS and DTR of the RS232 interface. At a PC environment this is done by the easySoft and also the OPC server.

That's the reason, why a PC-CAB doesn't work with a modem, because the control lines CTS and DTR can't be set properly. The MO-CAB (also an USB-CAB) instead contains a DC/DC converter to supply the opto couplers, the little trick with the control lines isn't necessary.

If you want to use the PC-CAB anyway, especially in an experimental environment, you can find a solution with an external additional power supply here:

http://easyforum.regulski.com/ef_berichte_usbadapter_en.html

If you want to build products for your costumers, you should use the MO-CAB as a more serious and professional solution.

Best regards

Bernhard

[John_Ess]

We have some small experience with connection of EASY8xx to HyperTerminal running on a PC. It is used for a very low level data logging during test runs. In the beginning we tried to figure out the possibilities and found out, that the use of PC-CAB didn't work. It is possible to get a connection but HyperTerminal is not receiving any data. We never digged deep enough to find the reason. The MO-CAB however was working fine.

I finally figured out what's needed for PC-CAB to work with HyperTerminal. The culprit was not a PC-CAB itself but a classical case of lack of remote control of DTR line from inside HyperTerminal and most of other simple terminal emulators.

If you use a terminal emulator that can control DTR line ON/OFF then your PC-CAB can be "powered" from that line, and will be able to communicate data from easy800 to PC without any problems. Use Bray++ for example and the so called "power" problem's gone!

Some 6 years ago Otto Birr posted a little note on similar subject that can be found elsewhere in this forum.

Inside that appnote Otto described small modification that's required for easy800-PC-CAB to be used with ANY serial device. And yes - that means that you can communicate - even with HyperTeminal   

All that's needed is to ground pin 4 (DTR) inside DB9-F end of PC-CAB. By setting DTR line LOW you actually supply the missing optocoupler's Ground, and thus "power" the PC-CAB.

I found that the easiest way to modify it is to open cable's plastic shell and solder a jumper (use wire or 2-pin jumper)  between the associated pins 4 and 5 directly on a pc board found inside the shell. In my case (see pictures below) the colours of the wires to be jumpered together were YELLOW (pin 5 = SGND = Signal Ground) and GREEN (pin 4 = DTR).

That's all folks. You can close the shell and leave such modified cable to be used from now on for anything you wanna do with it...

Or you may want to add a little ON/OFF switch between 4 & 5 and hide it inside PC-CAB's shell, or you may opt for building a detachable plug-in gadget as per Otto's write-up.

Anyways, after modification the optocoupler found inside PC-CAB becomes permanently enabled to send data from EASY800 without any need for "handshake" setup or lack of it.

After all - and despite some other rumours - your PC-CAB cable can be used for both easySoft programming, and serial communication of your choice.

Thank you Otto Birr!

p.s. It is worth to mention that Otto's elegant contraption (with additional power to pin 7 and some line drivers of course) allowed to communicate 1000m apart as reported by Frank some 4 years ago here

http://easy-forum.net/index.php?topic=882.0

und

http://easy-forum.net/index.php?topic=880.msg3287#msg3287



 

[avirules]

hii dude,



i have an easy822DC-TC with .i am required to extract the counter value through serial port using rs232. i am using easycom40 protocol and developed the codefor this using c. but the plc is not responding.

i am using a cable from AB(1760-CBL-PC01) . is it because of that or should i use EASY-MO-CAB

i have set the necessary baud rates n all according to protocol specification


can you plese tell me what is the problem.