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I would like to imagine that by reaching this part of my site that you�re well into the idea of constructing that first project! Maybe you�ve come up with an idea that�s been in the back of your mind for some time, or alternatively, you may have had a few ideas from the projects described on this site. Perhaps now is therefore the time to think about what might be deemed an �ambitious� first time project, or better described as one that can be set aside until a little more experience has been gained with lesser undertakings? OK. So let�s look at a few of those areas that I would be inclined to avoid in a home micro project: |
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DMA controllers |
Although dynamic memory access controllers might well be deemed essential to the designer of a complex computer system, I�ve never seen the need for one in any of my HOME projects. (Also see my remarks on Dynamic RAM usage below) |
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Dynamic RAM |
Compared to dynamic RAM, static RAM is now at a price where the additional complexity of the dynamic RAM refresh circuitry is really not worth while battling with in a simple home project circuit - unless you are intent on piling on the megabytes..! |
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CRT controllers |
CRT controllers such as the 6845 are well within the programming capabilities of the home micro constructor, but are really best avoided unless a thorough knowledge of TV principles and TV interface circuitry is available. I may be persuaded put a full working example up on this site if there is sufficient interest for me to do so. |
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Out-of-family LSI devices |
Preferably don�t! Whilst some peripheral LSI chips will work with most processors, there are others that are nigh impossible to interface with another processor family. When in doubt leave well alone and use only compatible devices! |
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Complex interface devices |
We all like to add something a bit �special� to our projects from time to time, but be careful about going overboard with special interface devices as software / handshaking routines and manuals can be sometimes rather difficult and expensive to locate. |
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Multiple interrupts |
Interrupts might be wonderful things, but can be a real pain to incorporate into a home project, so use only if really necessary. Bear in mind that debugging the software model for a multiple interrupt home project can be literally a nightmare! |
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Very fast bus/clock speeds |
The moral here is to take care and keep the speed down. Remember that breadboard construction will start to misbehave if high speed clocks are introduced into the wiring runs. An upper limit? With a little care, 6Mhz should be OK in the majority of projects and applications. |
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Audio processing projects |
The idea of audio processing using a micro is fun - I�ve done it a number of times. Problems? Crosstalk into the audio chain, use a good fast A-D and D-A. Take care with any pure audio wiring and keep it well screened! |
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Video processing projects |
Video is very difficult unless you have a thorough grounding in analog and video techniques. Take a look at my Televideo project if you�re interested. Remember too, that ordinary micro�s are TORTOISE slow for manipulating ANY form of live video signal. |
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SCSI, IDE, PCI etc. |
The idea of interfacing to one of the PC- type interfaces might seem appealing, but see if you can source the necessary interface information BEFORE attempting to design that project! |
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Floppy disk systems |
Floppy disks might seem the ideal storage media for the home micro contructor, but things are not that simple. Avoid unless you are prepared for a lot of hard work in the software dept. First and foremost you�ll need some form of operating system... See my UDSS storage project for some useful information and a circuit that can probably be adapted. |
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Arithmetic projects |
For the mathmaticians amongst us, the programming of binary arithmetic may seem like fun. It is - up to a point. Therefore don�t go for an electronic calculator project unless you have advanced skills in this area. |
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I know it�s all very well talking of the projects that are best avoided, so what about some more positive ideas then? Whilst I am fairly sure I�ll never undertake all of these ideas, I�ll probably have a stab at most of the following - eventually.. 1) An in car computer. Not something that is difficult, though it might sound it to most! The only awkward things needed here are interfaces to the car itself. For my own project that I�m going to start any day now(!), I�m interfacing with a pair of simple inductive sensors for the electric fuel pump and the engine speed, and am using a hall-effect device triggered by a magnet on the back of the speedo to detect road speed (I�ve already made and tested this bit!). A few thoughts at the programming side and I�ll soon be able to measure MPG, fuel used, average speed etc. etc. 2) A simple data terminal with alterable settings. Something that�s always useful with comms users. Can�t decide on whether to go for an interface to a standard PC AT keyboard and VGA monitor or to go it alone with an LCD and home brew keyboard. Probably both avenues will be about as complex in the end... 3) And now a nice and simple one, a micro based central heating controller! Now here�s something that�s genuinely EASY to make / program, USEFUL into the bargain, and will be adaptable to one�s own particular central heating system! (Been there done that, completed October 2002!) Of course, if there is no desire to make a software clock inside, why not go for a real-time-clock chip? My �Mighty Mentor� uses one as I couldn�t stand the thought of mating all of my programs into the timing loops! Particularly as it has the facility to write and run simple programs from the hex keypad... In the end I used all of the facilities the clock chip offered, including the stopwatch and the day-date-year calendar. |
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And last by no means least we have the �experimenters� projects, where the limit is set by one�s own imagination! Test equipment, physics experiments, a strain gauge turned into a set of accurate electronic scales, a thermister or two used for accurate proportional temperature control, experiments with stepper motors and servo�s, and if you invest in some modellers gears, I�ve even heard of a pen / polar plotter being a viable project to consider. You have a similar idea? Then go for it! |
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