Abstract:

Digital Circuits is an obligatory course in the curriculum of Mechatronic Engineering and Biomedical Systems Engineering of the Engineering Faculty of the National Autonomous University of Mexico (FI, UNAM). This course seeks for students to apply low, medium and high-scale integration devices, as well as different methodologies and tools for the design of digital systems. To reach this goal, it is necessary to have access to programmable logic devices like GAL with its development software. Although the University laboratories are well equipped, it is necessary for students to acquire it and it is difficult to achieve it in addition to its high cost in relation to other components that most of the students cannot afford. Therefore, it has been a priority to look for alternative software and devices that students can have access to in order to have the appropriate academic training.

Then, the objective of this article is to verify if a PIC microcontroller together with the library file PLD.h could work as a hardware replacement tool, with quite similar language as logical expressions used to perform calculations. The aim of this work is to show the experience of the FI, UNAM, using PLD.h library to program PIC microcontroller in the Digital Circuits course and how the objective could be reached.

The proposed methodology was first to create a library file with which it was possible to use a PIC as a GAL, later to apply it in class, evaluate if the students were able to implement it in the circuit design and make the necessary adjustments to improve this idea.

The PIC microcontrollers designed to be used in the library file are: PIC16F887, PIC16F1939 and PIC18F4550. An integrated development environment (IDE) with the PIC C CCS plug-in is necessary to be able to use the PLD.h library and to create a project that links the microcontroller. The PLD.h library integrates the configuration, memory addresses and definitions for the correct operation of the microcontroller as PLD.

In relation to the results obtained, since 2016, PLD.h library has been used to program PIC microcontroller every semester in the Digital Circuits course of the FI, UNAM. The students have been trained in the design methodology and programming using PIC as a PLD with PLD.h library, with the feature of inputs and outputs, as well as the definition of logical expressions.

To make the hardware more accessible to students, a development board has been used based on PIC microcontrollers that includes all the circuits for its autonomous operation through the USB port of a computer. This makes it possible that students can work at home in the implementation of their practices, without the need to go to school to program their circuit.

In conclusion, the substitution of PLD by means of a PIC and the software tool has made possible to maintain the objective of providing comprehensive and meaningful learning to students of Digital Circuits, based on simple and economic physical-digital machines implementation seen in class.

Keywords:

PLD.h library file, microcontroller, GAL, digital circuits teaching/learning, programmable logic devices