Please don't flame me but I don't have a clue about ModBus. I was given the job of creating an interface between a washing machine and a Sco Unix OpenServer 5.07 server through a serial port….. That was my brief. I discover I need to use ModBus protocol to manipulate the register on the controller a bit more complicated but I’m not too scared yet… Can I first check I’ve got the right idea, there’s a serial port on the control you connect via a serial port with a client package (logon) then peek/poke away? Is there a client package for SCO? If not is there a windows PC copy? I would really appreciate some advice. I have downed some ModBus documents any suggestions or URL’s to read up on are also welcome.

Regards, Michael.

 

Dear Mr. Fernandez,

Modbus ASCII is a serial character-oriented protocol. Any software writing ASCII strings with Modbus commands may use the serial port to obtain data and send commands. The Modbus command specification can be found on the Modbus web site. Here is a link that will get you to the specification:
http://www.modbus.org/default.htm

You should select the "Modbus Standard Library" link and accept the conditions. All of this is free. Then select this option: "Modbus application protocol V1.1 - December 2002" (a pdf) One of the reasons for using Modbus is that this specification is widely available and it is character-based. All you would do is "print" to the serial port from C or C++. The returned data is packed into 7-bit ASCII characters which you would need to decode, but the formula is in the specifications.

Have fun with this.

Dick Caro
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Look to the community, almost any client for Linux should compile on SCO as well. You'll need a C compiler, either SCO's (expensive) or GCC. Since a washing machine can't have much of a variety of functions, the simpler demos should work for you.

Regards

cww