Some of the data acquisition systems developed for PCs in the mid ‘90s are still used in the industry up to this day. Changing these to cheap, but reliable devices can be done using Raspberry PI computers. Relating to this problem my task was to implement the communication and user modules of a data acquisition system, which was originally developed for DOS, in a Raspberry PI environment.
During my work I got to know the data acquisition system written in C and x86 assembly language, as well as the standard and non-standard communication protocols used by the system, which I implemented successfully in the new environment.
In the second chapter of my thesis I will introduce the main development stages, modules and functions of the original system.
In the third chapter I will briefly summarize the hardware components, technical parameters and development environment of the Raspberry PI.
In the fourth chapter I will explain the main features and commands of MODBUS protocol that the data acquisition system uses for serial communication with the PLCs connected to it.
The fifth chapter of my thesis discusses the steps of implementation and the emerging problems. Because of the different hardware platform and software environment several parts of the original source code had to be modified. We take a detailed look at the structure of the communication modules and the scheduler. Modification of the scheduling was necessary because of the differences between the two operating systems. The original system under DOS was using a non-preemptive scheduler. I will show the implementation of this in a multithread environment.
In my thesis I will introduce the main components of a modern web-based user interface. To create the web user interface I used a flexible development environment, the Python Flask framework.