BTEC units 62 and 68

[Benj]

Many of you will be aware that the BTEC National has changed and that there are two units that now cover microcontroller/microprocessor programming. Here we look in brief what this means to you:

Unit 62 - Microprocessor systems and applications

This unit is designed to give students an understanding of microprocessor systems and experience of programming a microprocessor. The crucial detail about this unit is that it does not tightly specify which programming software you should use. You have a choice here: C, BASIC, Assembly code, flow charts Pascal and others. We believe that the best choice is to use Flowcode: Flowcode allows students to construct programs using flowcharts which are compiled directly to a microcontroller chip. This is the easiest way of teaching students programming as it is the system in which programs are planned, it requires no understanding of syntax, and it allows students to simulate and understand their programs before downloading them.

The hardware requirements are adequately covered with E-blocks or our version 3 development board.

The bit I do not like about this unit is that it is very confused: much of the grading grid is microprocessor orientated and yet the guidance notes state that microcontrollers can be used which would not naturally fulfil grading criteria. The unit is still microprocessor orientated and it mentions that students must understand tri-state control, address decoding and the use of chips like the 74LS138. In my opinion this is very old fashioned: microprocessors are almost extinct in modern electronics – the only time they are really used is in desktop PCs. These days the microcontroller is king and issues like address decoding are relatively unimportant issues in hardware design – although they still have a place in the study of computer chip architecture design.

The bulk of the learning objectives are covered by our curriculum CD ROM ‘An introduction to microcontroller programming’. If you would like a free single user copy then please get in touch with Justin.

There is a small section that indicates that you must teach students how to design microprocessor systems with ElectroMagnetic Compatibility in mind. I am not quite sure how you do this and would like to hear from readers who can explain it to me.

Unit 68 – Principles and application of Microcontrollers

At last – the word ‘microcontroller’ has appeared in a unit! About time! That’s the good news. The bad news is that the rest of this unit confuses me even more than unit 62, so please bear in mind that this interpretation of what Edexcel might accept could be flawed.

The hardware that you might use could again be our version 3 development board or E-blocks (based on PIC, AVR or ARM microcontrollers). E-blocks would be more suitable as the unit makes significant reference to communications systems which implies more than one microcontroller in a system. I see in the specification that Edexcel is encouraging you to look at the possibility of using devices from ‘Western Design Centre’. This company manufactures 65xx devices like the 6502 and the company’s web site strap line “Legendary 65xx microprocessors keep on cranking”. ‘Legend’ is the appropriate word here – if one of your goals is to equip your students with skills for the modern world then ‘Legends’ are probably to be avoided.

Your main dilemma in this unit is the choice of software – for a unit of this level you should be teaching your students assembly code or C code. The issue of Real Time Operating Systems is a key factor – RTOS and assembly code are not really compatible. If RTOS is on your list of things you want to give your students actual experience of then you will need to teach C programming. In any case the advantages of RTOS are explained after interrupts are studied and interrupts are easier in C than in assembly. Adding weight to the argument for teaching C code programming is that this is the skill industry needs (the arguments for programming in assembly are diminishing each year) and almost all universities we speak to have now moved to teaching C. Appropriate software and curriculum can be found on our three CD ROMs, including ‘C for 16 series PICmicro microcontrollers’ which contain complete courses on C programming and include C compilers and the development tools you will need. A weakness of our products is that RTOS is not covered. I am not sure we will change this: our customer feedback makes us believe that the subject of RTOS is best left to a further module on microcontroller programming as there is more than enough work for all but the brightest students in covering the basics of C or assembly programming.

If this article reaches the person who wrote this unit then please get in touch – I would very much like to know more about how you envisaged teaching it.