[sdiy] Beginner questions

[Richard Wentk]

At 12:19 24/02/2003 +0100, Oliver Keller wrote:

>So this is my situation : I´d like to build a hardware sequencer, mainly
>because I can´t buy what I want to plus I´m very interested in
>understanding the technology behind.
>
>It may be a pretty big thing to start with, but I don´t expect fast results, I
>accept a learning curve for this topic !
>
>Right now, I´m working on the definition of what the system should be
>doing, but soon I will need to decide about programming language,
>software structure, processor type and model plus all the hardware issues
>like what brand and model of pots, switches etc.

Well,  it really depends on how complicated you want to make this. It's 
entirely possible to build a simple step CV sequencer without using a 
processor at all. (I've done this with a breadboard circuit where you 
programmed the steps by plugging in different resistors. :) I seem to 
remember, without looking it up - so this might not be totally reliable - 
you need a 4017 and not much else.)

It's not that much harder to add some memory to this so you can switch 
between different pre-programmed sequences or choose manual mode.

You only really start needing processors when you add an LCD display, and 
various clever features like note quantisation to a set of pre-programmed 
pitch classes. (So you can transpose your sequence from a keyboard and it 
will stay in key - not something you can usually expect of a bog standard 
analogue design. Although you could add a processor free scale programmer 
quite easily.)

>Is there any FAQ out there or some tutorials that give a computer guy
>some ideas about the electronic side of this ? I´ve seen that there are
>some machines based on PICs, others on VARs, other on 68xxx, but I don´t
>know why to prefer this or that way.

If you're treating this as a learning experience rather than as a 
straight-out attempt to build a tool you can use right away, I'd seriously 
suggest looking into a simple processor-free design first. You'll learn a 
lot more about basic electronics that way, and also appreciate why you 
might/might not want to use a processor, and what kind of enhancements it 
can give you.

H/ware design and s/ware coding seem to require different mindsets. S/ware 
is much less hands-on and physical than h/ware, and your mind works in 
different ways to solve different puzzles. If you have s/ware experience 
already, it might be interesting to try to learn to solve problems in a 
h/ware kind of way.

It's not that one is better (although one may definitely be better for 
certain problems) but more that they're different in interesting ways. 
Having experience of both is definitely more useful than just being fluent 
in one or the other.

>Would this list be a good point to ask about sequencing stuff as well ?

Almost certainly. :)

Incidentally a standard recommended book is The Art of Electronics by 
Horowitz and Hill. It's not cheap, but it's one of the best introductions 
around.

Richard