Who developed the ModBus protocol?

The Modbus protocol was developed by Modicon, now a brand of Schneider Electric.

It was originally designed in 1979 for use with its programmable logic controllers (PLCs) in industrial applications.

Modbus is a serial communications protocol that has become a de facto standard communication protocol and is now commonly used to connect industrial electronic devices. The main reasons for its use are its simplicity and the fact that it is open-source, which allows manufacturers to build their own implementations of the standard.

References

"Modbus Protocol Reference Guide," Modicon, Inc., 1979.

"A Guide to the Modbus Protocol," Schneider Electric.