[Feature Request][MODBUS]: Build a QueryOptimizer for PLC4J Modbus

[chrisdutz]

What would you like to happen?

The modbus spec seems to provide limits for the size of packets. However in contrast to the other protocols, is this limit not related to the size of the packet, but by the number of registers/coils.

Please refer to: https://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf, page: 11

It should be simple to implement a query-optimizer for Modbus to automatically handle this. The Siemens S7 QueryOptimizer might help with inspiration.

Programming Languages

• plc4j
• plc4go
• plc4c
• plc4net

Protocols

• AB-Ethernet
• ADS /AMS
• BACnet/IP
• CANopen
• DeltaV
• DF1
• EtherNet/IP
• Firmata
• KNXnet/IP
• Modbus
• OPC-UA
• S7

[chrisdutz]

So it seems that the limitations are:

Max 2000 coils in one request (Page 11)
Max 125 registers in one request (Page 15)