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An Undergraduate Microcontroller Systems Laboratory

Mark Hedley, Member, IEEE, and Simon Barrie


Abstract - This paper discusses a course in microcontroller system design which was revised to facilitate improved student learning outcomes. The course aimed to develop design and technical skills, as well as communication and team management skills. A Problem Based Learning (PBL) approach was taken, and the focus of the course was on the laboratory where the students worked on a major design project. Hardware was developed for the laboratory using the Motorola 68HC11 microcontroller which enabled the students to undertake a range of design activities. The students formed groups and were assigned a realistic design project to undertake over a semester. Evaluation of this course was obtained from students, staff and an external reviewer, and the results show that the revised course achieved its educational objectives.


I. Introduction

The use of microcontrollers in industrial and domestic electrical devices has become ubiquitous over the past decade. Electrical engineers need to have an understanding of microcontroller systems, both hardware and software, but incorporating the topic into the core undergraduate curricula poses a number of challenges. For students to gain a deep understanding of microcontroller system design there must be a practical component to the course where they can implement and test their designs. The main challenge is designing a laboratory that satisfies the educational objectives under the resource constraints of large student numbers, limited available student contact time, and a small budget for both equipment and teaching assistants. Other challenges are to provide a curriculum that inspires the students to learn and to develop other skills such as the ability to approach open-ended problems and to work in teams.

At the University of Sydney all electrical engineering students are required to take a course on microcontroller systems design in their second undergraduate year. This course runs for one semester (13 weeks), and has two lectures per week (one hour each) and one three hour laboratory session every second week (total of 21 laboratory hours). In this paper we will outline the course and laboratory equipment that was developed and discuss how the Problem Based Learning (PBL) curriculum supported student learning.


II. Course Objectives

The learning outcome specified for students taking the course was that "at the end of this course you will be able to design a simple microcontroller system for real applications." In addition to this specific objective, all courses should develop engineers professionally. To achieve these outcomes the following objectives were specified for the laboratory component of the course:

  1. To provide practical experience with microcontroller systems;
  2. To expose the students to design work where there is no single correct solution, rather competing objectives; and
  3. To encourage cooperative team work and develop communication skills.

The nature of the design process requires students to develop a design which represents the 'best solution' given a set of specifications and the limitations set by the parameters of microcontroller systems. Such a task requires, amongst other skills, an understanding of the applied principles of microcontroller systems. While students had been provided with relevant theoretical knowledge through lectures and texts, the ability to apply such principles in real settings was the desired outcome of the course and students required support to achieve this level of learning outcome. The first objective was therefore to provide practical experience in such application of knowledge as a basis for reflection, and experiential learning.

The second objective also related closely to the nature of the design task. Design is essentially a creative task. There is typically no single correct answer and students and practitioners are faced with the challenge of developing novel solutions to unfamiliar problems in an unfamiliar setting [1]. In light of this challenge it follows that students are unlikely to be prepared to meet such a challenge simply by learning how to replicate the solutions used by others in the past. As such the second objective for the laboratory component aimed to expose students to realistic, challenging design tasks where each student would be prompted to consider both the nature of the tasks and the design parameters. On the basis of such consideration students would be encouraged to explore and develop a range of design strategies to address the unique requirements of each task. The provisional nature of knowledge and the non-arbitrary nature of design solutions would be emphasised in the solution to diverse real tasks.

In Australia there has been a strong movement in recent years for the development of "generic attributes" of graduates, where these are defined as "skills, personal attributes and values which should be acquired by all graduates regardless of their discipline or field of study" [2]. In 1988 the Williams review of engineering [3] found a significant gap between employer expectations and graduate competencies in communication and management skills. The Institution of Engineers, Australia, responded by ruling that the content of all engineering curricula must contain at least 10% management education [4]. In 1993 the University of Sydney produced a policy document [5] on the development of generic attributes of undergraduate students. Generic attributes such as the ability to manage a small project, work cooperatively with group of people, and communicate the results of the project both verbally and in written form are important skills that can be developed with a well designed laboratory project.

In the course taught prior to the one described in this paper, these objectives were not being satisfied. The practical component consisted only of programming exercises, with no exposure to hardware, and teamwork and communication skills were not being developed. The new curriculum described in this paper was designed to address these issues.


III. Course Design

A. Prerequisites

All students who enrolled in this course were required to have complete courses in Computer Science and Digital Logic in their first undergraduate year. They knew how to write computer programs, and had some exposure to assembly language programming in general, but not with the assembly language that was to be used for the chosen microcontroller. From the Digital Logic course the students knew how to design combinatorial and basic sequential digital circuits, and had worked on team design projects.

B. Use of Problem Based Learning

Based on a consideration of the nature of the learning outcomes targeted for the course, teaching and learning tasks were developed based on a problem based learning model. Problem based learning (PBL) is a model for developing curriculum and teaching methods using real problems as the focus of student learning [7]. Structuring student learning around problems has been used successfully in courses in other fields of engineering [8]. Problem-based learning is considered to foster active involvement by students in their own learning. It is an effective strategy for developing in students the life long learning skills necessary as future members of a profession with an evolving knowledge base. In addition the approach advocates the development of the skills, knowledge and attitudes most relevant to professional practice. The analytic and creative problem solving skills central to the design process are a focus of PBL. Student satisfaction and motivation in PBL courses is high, due in part to the perceived relevance of their learning tasks to their future professional activities. In addition, it is clear that students learn best in those situations where they are actively involved and are learning knowledge in a similar context to that in which they will later be expected to apply it.

The focus of this course is on the laboratory, where the PBL paradigm can be applied. The lectures provide the basic knowledge resource which is applied in the laboratory to find solutions to problems in the limited available time. The lectures are also used to provide a number of design case studies. The laboratory consists of a set of introductory exercises to familiarise the students with equipment and assembly language of the microcontroller, then for the remainder of the semester the students work in a groups on the "design exercise" where they design a microcontroller system for a specified application.

C. Course Content and Assessment

To focus the student learning on an understanding of the principles underpinning the applied problem solving activities of microprocessor system design the course was based on a single microprocessor. More abstract generalisations are pursed in a subsequent course on Computer Architecture. The microcontroller that was chosen was the Motorola MC68HC11E9, as it is widely used, is readily available at low cost, and has a wide range of internal devices. The course syllabus was as follows:

  1. Introduction to Computer Systems and Microcontrollers (2 lectures)
  2. Programming the 68HC11 (4 lectures)
  3. Hardware Overview of 68HC11E9 Microcontroller (3 lectures)
  4. Bus and Memory Interfacing (5 lectures)
  5. I/O Interface Concepts (2 lectures)
  6. I/O Interfaces - Parallel, Serial, and Analogue (3 lectures)
  7. Timer System and Real Time Control (3 lectures)
  8. Designing Microcontroller Systems (4 lectures)

The textbook chosen for the course was by Spasov [6]. The book provides a useful reference for most of the material in the course. The lecture topics do not closely follow the book, but the students are expected to be able to use the text to find information not covered in lectures.

The assessment consisted of the introductory laboratory exercises (15%), the design exercise (40%) and the end of semester examination (45%). These assessment weightings were determined by negotiation with the class.


IV. Laboratory Design

A. Equipment

In the laboratory it was desired that the students not only be able to program microcontroller systems, but also to have control over the hardware implementation of their designs. In the short time the students have available it is not possible to design and build a complete microcontroller system from scratch, so a modular approach to the hardware was taken. The Motorola 68HC11EVBU board was used as the basic building block. This provides the 68HC11E9 microcontroller with the BUFFALO monitor program and a serial connection that is used to download and debug programs. The programs are written and assembled on a PC. The microcontroller board has an expansion connector which is used to connect the microcontroller board to other printed circuit boards (PCB) containing additional hardware for laboratory experiments.

We have designed two PCBs for use in the course. The first one is for the introductory exercises, and contains two multiplexed seven-segment displays, a potentiometer for a 0 V to 5 V analogue input and a button. The second PCB was developed for the "design exercise" and contains a number of modular units including switches, motor, IR transmitter and receiver. There is a patch area on the board that allows the students to connect signals between the modules and the microcontroller. In this way the students have great flexibility in configuring the hardware, without having to completely wire the circuit. In a planned revision to the second PCB, the components of the first PCB will be included so that only the one board connected to the microcontroller board is needed. We will now describe in more detail our second PCB, which we call the "design exercise board", as it is the key piece of equipment for our PBL teaching strategy.

The design exercise board was designed so that a number of different projects could be attempted using the same hardware. To achieve this a number of independent modules that can be configured for a wide variety of tasks were implemented. These modules are:

Besides these modules, it was found that the memory on the Motorola 68HC11EVBU (512 bytes) was inadequate for the intended projects, so the design exercise board adds an additional 8 kilobytes of memory to the microcontroller. The components of this board are illustrated in Fig. 1.

Fig.1. The modules and main components of the board that was built for the design exercise.

With the limited resources it was important to keep the cost of this as low as possible. The cost per bench, which includes a 5 V power supply, Motorola 68HC11EVBU, and the two PCBs that we designed and built, was approximately US$250. This does not include the cost of the computer at each bench position, which was already available in the laboratory.

B. Introductory Exercises

At the start of the semester the students completed a set of exercises. These were designed to familiarise the students with the equipment, the assembly language and the use of the 68HC11 microcontroller. These four exercises taught the students to:

Once these had been completed the students were ready to start their design project.

C. Design Project

For the design project the students formed groups of their own choosing with between three and five members. Each group was assigned a project out of a pool of six by the lecturer. Each project was designed to be easily divided into a number of subtasks, and it was expected that each group would partition the project and assign tasks to each member. With these projects the students were exposed to a substantial design problem, and to solve it they needed to work cooperatively within their team. At the end of the project each group submitted a report.

This arrangement also had the advantage that it eliminated cheating from the design project. With only five or six groups on average doing the same project, and with the large range of feasible solutions, any copying was very readily detected.

The students formed into groups and were assigned their project a few weeks into the semester. It was expected that they would have group meetings to brainstorm for possible solutions, then assign tasks to each team member. Basic decisions about the hardware allocation would need to be made early by the team, then individuals would be assigned tasks such as algorithm development, coding, and documentation. Each team also needed to select a leader.

The report had to document the hardware and software algorithms for the solution proposed by the students, then provide details of the implementation and testing. This report was assessed on both the technical content and written communication skills of the group.

Using the hardware a large number of projects are possible, two examples being:

D. Design Project Assessment

The assessment for the design exercise also used "real" criteria. The mark for each project was determined from a test of the final system in the laboratory to see how well it complied with the given specifications (one third of the marks), and the remainder of the marks (two thirds) came from the report submitted at the end of the project.

To provide an assessment for each student, each team member was required to score all members of the team (including themself). The mean mark for each student was calculated, then the mean of the top three student marks (as the minimum group size was three) became the base mark for the group. A weighting for each student was found by dividing their mark by the group base mark. The final mark was the product of this weighting and the group project mark.


V. Evaluation

In seeking to evaluate the effectiveness of the new the laboratory course, data was drawn from a student focus group, written responses from staff and excerpts from an external review of the department courses. Additional data relating to learning outcomes was gathered from a consideration of the student's exam results and their results on the design task assessment.

The evaluation sought to determine whether the revised laboratory component promoted the intended student learning outcomes and whether there were additional strategies which should be implemented in future courses.

A. Student Feedback

Student feedback was gathered from a focus group interview. The students reported finding the teaching and learning experience of the design exercise interesting. They noted that the exercise promoted understanding, "I found myself...understanding stuff at a dramatic rate". The task addressed the issues of student interest and motivation as well as improved perceptions of their own learning outcomes, "If we don't get involved in projects like this....we would come out with no real thinking power or problem solving ability". The nature of the task was seen by students to be relevant to their needs as future professionals, "Well engineering is basically about creating something that is useful and design is integral to creating something - this is basically the whole point". Student comments also indicated that they perceived they had developed communication skills and group work skills consistent with the objectives of the course.

The students' performance on the exam (i.e. staff assessment) was compared with their assessment results from the design task in the laboratory component. Both these assessments focussed on the skills and applied knowledge covered in the design task. The results are reported in Table 1. A strong correlation was observed between results on the two assessment tasks suggesting that students' self assessments correlated with staffs' and further supported the conclusion that students had achieved the learning outcomes specified for the design project, in fact they had developed accurate self evaluation skills.

TABLE I
Comparison of staff assessment (exam) and student assessment (design exercise) by comparing design group rank.

 

Design Exercise Rank

 

 

 

1

2

3

4

5

N/A

Exam Rank

1

17

3

1

1

0

0

2

13

3

2

1

1

0

3

6

3

9

2

1

0

4

3

3

4

3

1

1

5

0

0

0

4

4

0

N/A

0

1

1

0

0

4

B. Staff Feedback

Staff opinion was sought with regard to the impact of the revised laboratory component on student learning. Staff comments from both colleagues in the Electrical Engineering Department and an external reviewer were overwhelmingly positive. It was particularly encouraging to have strong support from the senior academic staff in the teaching area, with one colleague writing:

These changes seem to inspire students as well as increase their confidence at approaching open-ended design problems which do not have clear solutions - an important change from many subjects where all questions have a correct answer. Project management skills are also strengthened with this type of project since students are forced to divide, schedule and communicate with each other.


VI. Conclusion

The introduction of a problem based learning model for teaching microcontroller system design was very successful, particularly given the resource constraints. Laboratory equipment was designed and built which enabled the students to experiment with both the hardware and software to implement a microcontroller system. The focus of the course was on a design problem that the students attempted in small groups, and this was supported by the lectures. From the staff and student evaluation we conclude that the new course was well received and that we have satisfied the course objectives discussed in Section II.

It must be acknowledged that there are some limitations with such an approach. We found that the students often had little confidence in their ability to approach a complex open-ended problem, and they needed to be eased into the work with smaller tasks to build up their confidence. Many students, particularly the high academic achievers, were also uncomfortable at having to work in teams, even though they clearly recognised that this will happened when they work in industry. The largest limitation encountered was the need to provide adequate human resources to support the student learning. For this type of open-ended student learning the demonstrators required a detailed knowledge of the subject domain and the interpersonal skills to act as group facilitators. Finding a sufficient number people with this combination of skills, and being able to adequately remunerate them given university constraints, proved to be a challenge, and raised issues to be addressed in staff development for future teaching / demonstrating staff.

Engineering in general has received recent criticism in terms of relevance of the curriculum and the teaching in undergraduate courses, and there is an increasing need to re-examine teaching from the perspective of student learning. The use of PBL as a teaching and learning strategy which focuses on active involvement of students as learners and a curriculum which is relevant to future professional work should go a long way towards addressing these concerns.


Acknowledgments

We would like to acknowledge the input provided by Bill Jelks from the Centre for Teaching and Learning, Robyn Cusworth from the Faculty of Education, and from the staff and students in the Department of Electrical Engineering, at the University of Sydney.


References

[1] J. Stephenson and S. Weil, Quality in Learning: a capability approach in higher education, London, Kogan Page, 1992.
[2] Higher Education Council, Achieving Quality, Australian Government Publishing Service, Canberra, 1992.
[3] B. Williams, Review of the Discipline of Engineering, Canberra, AGPS, 1988.
[4] Institute of Engineers, Australia, Policy on Management Studies in Professional Engineering Courses, Canberra, IEAust, 1990.
[5] The University of Sydney, Generic Attributes of Graduates of the University of Sydney, Adopted by the Academic Board, June 1993.
[6] P. Spasov, Microcontroller Technology, 2nd Ed., Prentice Hall, 1996.
[7] Boud and Felleti.(eds) The Challenge of Problem Based Learning, London Kogan Page, 1991.
[8] Cawley "The introduction of a problem based option into a conventional engineering degree course," Studies in Higher Education, vol. 14, pp. 83-95, 1989.


Author Contact Information

Mark Hedley
CSIRO Telecommunications and Industrial Physics
PO Box 76 Epping, NSW 2121
Australia
Phone: +61 419 253 955
Fax: +61 2 9372 4490
E-mail: Mark.Hedley@tip.csiro.au

Simon Barrie
Centre for Teaching and Learning
University of Sydney, NSW 2006
Australia
Phone: +61 2 9351 5814
Fax: +61 2 9351 4331
E-mail: S.Barrie@ctl.usyd.edu.au


Author Biographies

Mark Hedley was a lecturer in the Department of Electrical Engineering at the University of Sydney, where he obtained his B.Sc., B.E. and Ph.D. degrees. He is currently working as a Senior Research Engineer with the Commonwealth Scientific and Industrial Research Organisation in Australia. His interests include machine vision, video coding, industrial electronics and engineering education.

Simon Barrie is a lecturer in the Centre for Teaching and Learning at the University of Sydney. His interests include the design of quantitative and qualitative student feedback for evaluation of teaching and courses, problem based and experiential learning, competency based standards for the professions and implications for university education.