1 Dec
2010
1 Dec
'10
7:34 p.m.
Tony, you live in the seventies ;oD
OK, I meant the total compoent cost. If that was the primary design
criterion in all cases, we would have many fewer embedded PCs, for example.
You know as well as I do that the cost of the
chip is not the major cost
for a 1-off (or small run) project like this.
No, but the sum of all chips maybe are :) You might well have Z80s, EPORms, RAMs, etc in
the junk box (I certainly
do), but not the latest microcontroller
I have many microcontrollers in my junk box, and it doesn't need to be
the latest.
You may well feel it's a lot easier to solder
up a handful of DIL
packages on stripboard than a fine-pitch SMD packge that requires you you
to design a PCB first . This in turn may entail obtianign suitable CAD
tools, something to run them on, and finding a PCB manufacturer (or
buying the equipoment to do it at home).
:oO
- There are microcontrollers powerful enough for this task, and they are
all DIP - I can design a PCB at home using free tools
(Kicad rulez!)
For the nth time, the machien it runs on (and I susepct the OS it runs
under) are not free.
- I can make boards good enough for fine pitch SMD
at home (see my page,
http://tabalabs.com.br/eletronica/tts/index.htm) and the equipment is all
made from junk.
Excellent (I am not being sarcastic). Hwoever, building that equipment is
a project in itself (albeit an interesting one). If you just want to make
up a SCSI-drive rpelacement or whatever, why should you _have_ to make
the PCB stuff first?
Maybe it is time for you to update your prototype methods :)
Why? As I said in anotehr message, thsi is a hobby, why shouldn't I do it
the way I enjoy?
You may well know the assmbly language for the
Z80, and have the
assembler, etc. Not so fo rthe microcotnroller.
I know the asm for the Atmel microcontrollers. Also, I have the original (and free) assembler from Atmel. BTW, the programmer
is also cheap, 5
resistors on your parallel port can do the task. BTW, there are lots of
compilers for atmel microcontrollers, and they run on windows, DOS and even
linux. Since they are portable, I can do development on my Octane (Irix) or
in my PA9000. (still OS-Less)
Looking around, I don;t think I can see _one_ machine here that could be
used for that. You mention a programmer conissiting of a few resistors
ona a parellel port. I've got pletny of GPIB ports here, but I guess
that's not what you meant. OK, what about an HP9817 with an HP98522 GPIO
card? It probably could program an Atmel processor, but I'll bet the
software doesn't exist...
It's a darn sight easier to debug something
when you know what it should
be doing and can see what it is doing. The former is much easier to
determine for a Z80 than many modern processors (where the instructions
are not necesarily executed one at a time in the order you expect). The
latter is also much easier to do on a system with external program memory
where you cvan conenct a logic analyser to the ROM address lines.
In modern processors I can use cheap debug tools (which are CHEAP, look
for the price of the AVR Dragon which is an excellent USB programmer and
debugger via 1-wire. Ah, cheaper than my cheap logic analyser). And I can use (free) simulators to see the code running on my
screen.
I'd much rather know what my hardware is actually doing than what some
simulator things it's doing. The fewer uncertainties the better!
If you want a design to last as long as the
classic computer it's
connected to, I would certainly go with the Z80 + memory solution. Z80s
are very common. The microcontroller may be common _now_, but whata bout
next year. There are som many fariants with different memory sizes,
internal peripherals, etc that several times I've needed to find a
replacement for something made a few years ago onlky to find that that
particualr chip is rarere than hen's teeth. Oh, there are 'improved
versions', but they are not drop-in replacements.
Tell me a microcontroller that was common yesterday and isn't today. I also feel
that this idea of always making everything as cheap as
possible is a big mistake. It seems to lead to poorly made products with
all sorts of corners cut. As I have said many times before, I can think
of plentyy of examples where the cost to do it properly would add perhaps
\pounds 1.00 od xomponents. Say that translates into \pounds 10.00 by the
time you've added in all the otehr costs. That increase in selling price
would not have stopped me buying the product. But when I see how many
corners havec been cut, I am not goign to be happy, I am not going to buy
any more products from that company, I am goign to tell my friends to
look elsewhere too.
Of course, as fewer devices on board, lesser problems of design,
manufacture and repair I'll have. I'd prefer to use an internal program