On Mon, 2008-01-28 at 05:02 +0000, Chris Morley wrote: > I would think a loadable config file would be nessasary as every > device is different as far as how many, what type ,and what address of > the device/data. That seems to be why MUDBUS was used so much - they > didn't force much format to the data packets.
Every time I read the Modbus specification I realize something new or that I misunderstood. I thought that I could treat Modbus coils and registers like parport pins, the function of the pin is determined by what you hook to it. > If you had a loadable config file your module could load that file > then make HAL pins to suit. Then you would only need one MODBUS module > -it would just load different/more configs for different devices. > Classicladder uses this type of idea. It has a config window that you > set all this info and assign varriables to MODBUS addresses. You can > set it to access data in multiple discontigous ranges. It is loaded > when you load the ladder program. I like this idea, but I am getting used to creating a custom module for each piece of hardware. I am leaning towards having a macro that could be used to automate the process like Stepconfig. I am having difficulty figuring out what Classic Ladder is because it seems it does a number of functions that I am used to thinking of as being separate. Is it an editor, software PLC, or user interface? > I am wondering what people are using to connect to their VDFs -MODBUS > wise. I have a VDF that uses rs-485 or rs-422 but of course I only > have a serial port. I have seen converters from serial port (rs-232) > to rs-485. I've heard of USB to rs485. I did see that MESA makes a > daughter board that plugs into the 5120 (which I use) that will > produce rs-485. The problem with that is a driver needs to be written > and worse, I lose alot of input/output I tend to not worry about I/O because I can always throw up to eight parallel ports into the PC. If I need more than eight, it's a small change in the EMC software. For the RS-485, I am planning on using an RS-485 transceiver on a serial port, and using Classic Ladder's serial_linux.c software as a model. I'm planning for an HAL component for the device which packages the data and a Modbus RTU component which sends any messages in a buffer through the appropriate serial port. Apparently CL talks to the serial port as if it is a file, which I believe all hardware in Linux is. I am not familiar with doing this in C, but it seems to be a common practice. My book on C has a chapter on low level file operations, so I have a reference and examples to work from. RTS will toggle send/receive on the transceiver, which is a mystery to me, so I guess I'll need to study how UARTS work in Linux (again). I think both components can be in user space, and the Modbus part may not even need to be an HAL component. > I'm going to go try to figure out how to make a branch of 2.2.3 for my > adaption of Classicladder V7.124 with MODBUS enabled. > Then I hope some of you can try it and see what needs to be done to > make it work as right now I have no way to test it. I am concerned that we may have some common ground with our projects. If I had a better understanding of what needed to be done, I may be able to help. > Chris Morley -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
