Multiple TCP Modbus Slaves

[Fred]

Matthew,

That should work. I think you're right in that you might have some class name confusion as people may view the slave at the device id level instead of the networking ip/port level as the new semantics are.

Not that I think it would be a big performance hit, but with the process images backed by a hashmap keyed by slave id, you don't have to do a linear search to find the requested process image.

I may keep my current implementation simply because my process image registry is a collection of process images keyed first by slave id and secondly by my concept of a slave configuration (allowing for more than one process image if a "spill over" process image is needed). This class is thread safe and handles the addition/removal of process images by my slave objects. That said, I think this logic could easily be moved into the ModbusSlave class where if necessary I can create my own implementation.

So the answer to your question is yes with the reservation on the class naming as you pointed out.

Regards,

Fred

[mlohbihler]

Good points. The class is now called ModbusSlaveSet and has this relevant code:

    protected LinkedHashMap<Integer, ProcessImage> processImages = new LinkedHashMap<Integer, ProcessImage>();

    public void addProcessImage(ProcessImage processImage) {
        processImages.put(processImage.getSlaveId(), processImage);
    }

    public ProcessImage getProcessImage(int slaveId) {
        return processImages.get(slaveId);
    }

    public Collection<ProcessImage> getProcessImages() {
        return processImages.values();
    }
...

I used a LinkedHashMap in order to preserve the order in which the process images were added in case the querying order is important to the user.

[skiv71]

hi, just picked up on this thread.... is this some sort of data source that gives mango the ability to listen on port xxx and accept modbus requests? thus making it a TCP slave? think i needs this :)

Neil

[mlohbihler]

This forum is for discussions around the Modbus4J product, which is used in Mango, but otherwise no associated. It is possible to get Mango to act as a modbus slave, but not trivial. If you need this, please use the contact page to request a quote.