While old, the modbus standard is very alive and kicking. Today you can still buy newly designed PLCs and frequency inverters with a modbus interface on top of RS-485, RS-422 or RS-232 as the primary, and sometimes only, interface. Attendees to this talk will get an overview of the modbus history, usage and standard. Different cabling topologies will be discussed and advantages and disadvantages of different physical layers are discussed. Attendees will get a demonstration of how to access modbus compliant devices, both ethernet and serial devices, using Qt’s classes. Examples on how to implement both masters and slaves for modbus using Qt will also be given. When leaving this talk, attendees will have gained an overview of how the Modbus part of Qt works and will be able to go home and interface directly to existing hardware as well as creating new modbus slaves. And yes, there will be hardware, cables and flashing lights.