- ... Actually, the original ELF-II (I had one, back in college) used individual Cherry key-switch buttons, each mounted separately on the board. I was justMessage 1 of 44 , Apr 17, 2013View Source
> My biggest concern is finding a source of hex keypads that would work with the PCB.Actually, the original ELF-II (I had one, back in college) used individual Cherry key-switch buttons, each mounted separately on the board. I was just looking for similar buttons for another project a couple of months ago, and they are a bit difficult to source at a reasonable price, but not impossible. I'll probably adjust the layout of the board a bit to accommodate currently available parts (the edge connectors may be another issue...)
- Sure, but in my mind the expansion boards aren t part of the Elf III board, just possible later add-ons.Message 44 of 44 , Apr 20, 2013View Source
Sure, but in my mind the expansion boards aren't part of the Elf III board, just possible later add-ons.On Apr 20, 2013 2:53 AM, "Paul Backhouse" <paul@...> wrote:[Attachment(s) from Paul Backhouse included below]
Snip from Mark G...
< The base Elf II had no EPROM. You may be thinking of the Giant Board
And Elf II's RPN Arithmetic and Lev III "full" Basic card also utilises 3
From: email@example.com [mailto:firstname.lastname@example.org] On Behalf
Of Mark Graybill
Sent: 20 April 2013 10:08
Subject: Re: Elf III, was Re: [cosmacelf] Re: Elf II PCB
On Apr 19, 2013 9:22 AM, "Lee Hart" <leeahart@...> wrote:
> On 4/19/2013 8:20 AM, urrossum@... wrote:
> > It seems to me that what Mark is going for here is to have the ELF-3
> > be pretty much "bare metal", at least in its base form. In other
> > words, there would be no monitor EEPROM, or at least it would be
> > optional, with functions like the keypad hex display and program load
> > done with "discrete" logic, not requiring the 1802 to be running
> > anything. I definitely found that this increased my understanding of
> > the system, and kept it from just being "magic".
> I'm thinking of it as a "bare metal" machine as well. But the "metal" we
> have today can do more than it could back then. For instance, the Elf-II
> had a monitor ROM, but it was only 32 bytes. You can't get PROMs that
> small any more (except old stock at high prices).
The base Elf II had no EPROM. You may be thinking of the Giant Board
> But you can get far larger EPROMs today, at far lower prices. So use one
> of them instead. Pick one that is inexpensive, easy to get, and easy to
> > Rather than EEPROM, I think flash would be the way to go.
> I'm guessing it would be an EEPROM, because the flash ROMs I know of
> require block writes. But there are EEPROMs where you can program single
> bytes with DIP switches on the inputs.
> > Providing on-board programming is very simple
> Does "simple" mean using a PC, special hardware adapter, and megabytes
> of special software? Is there a flash ROM that can be programmed
> *without* all this? My goal would be a setup where there's a ROM on
> board, but it's initially blank. You load little programs into RAM with
> the keypad, test them, and then save them in the onboard ROM.
> If this isn't practical, then provide battery backup for the RAM (to
> accomplish the same thing).
> > Interfacing to a PC should be easy, too. Get some form of the USB
> > loader on board, for sure.
For me that's an optional add on. I built my first serial port and cassette
interface for the II.
> I'm sure us experts want to immediately go to a PC for everything. But,
> I think that is exactly the wrong direction to go for a beginner. It
> leads immediately into a learn-nothing situation, where everything has
> been done for you.
> > Speaking of cheaper, it seems that many in this group grew up in
> > fairly austere circumstances - not "poor", but not with very much
> > money to throw around on hobbies; this was certainly the case for me.
> Me, too.
> > This forced me to learn a lot about how to accomplish things with
> > limited resources, and using different approaches.
> > Is it just my tiny sample group now (living in a relatively posh
> > suburb of Silicon Valley), or is this sort of experience much less
> > common now than it was in my youth (60's and 70's)?
> For 16 years now I've been going into 4th-6th grade classrooms and
> mentoring kids to build electric cars. We don't give them money or kits
> or parts or instructions; they have to INVENT their own solutions. See
> www.bestoutreach.com for details. I watch how they think, and how they
> work. Here's what I see:
> America is becoming a nation of haves, and have-nots. The "haves" are
> wealthy enough to buy anything they want. Their kids have easy access to
> all the latest and greatest toys. They don't have to earn their own
> money, or learn to economize, or make things last, or fix things, or
> make do with what they have.
> The have-nots don't have the money to live like this. They have no
> choice but to work harder, or do without. Their kids have to be more
> creative, imaginative, and self-reliant to get what they want, or even
> to survive.
> In my BEST classes, the "have" kids expect adults to do everything for
> them, and buy them whatever they need. They are lost and frustrated if
> we don't. Their solutions all revolve around getting someone else to do
> it for them.
> The "have not" kids are used to situations where no one helps them. They
> are the ones that scrounge up junk from a garage or dumpster, and invent
> solutions that no one else would have thought of.
> I think it is *good* for kids to struggle. It gives them a direct,
> personal reason to learn. You should see their eyes light up when they
> solve the problem THEMSELVES, without being given the answer! That is a
> priceless experience!
> The kids absolutely *love* the BEST program! It's often the first time
> in their lives that they've ever touched a real tool, or built anything
> that really works, or invented something themselves, without adults
> directing and micromanaging it.
> The sad thing is that the schools, and most parents, and society in
> general doesn't like it. It's disruptive. The teachers aren't in
> control, there's no lesson plan, and it's not on the state mandated
> tests. Parents worry that their little darling will be hurt by dangerous
> tools. We're teaching them to be scientists and engineers; not good
> little factory workers and consumers.
I've seen the same over the past 5-6 years. I see it as more of a split
between "does" and "does-nots". ;) It's less a matter of material
circumstances and more one of inclination among the kids I work with, who
are mostly lower middle class or poor. But some have iPhones and expect
everything to be a finished product all the same.
The past two years have been somewhat disheartening, in that I've had kids
that go through actually doing something, they feel great, then some break
happens elsewhere and they come into class more resistant than ever. They
usually end up dropping the class. There have been successes, those and the
students that really do come to learn pay for all, but the "conversion rate"
has been significantly lower and at high school level, especially, it's been
harder to get through.
On the plus side, the middle school classes haven't been as difficult.
Especially small class sizes for high school because of class scheduling
conflicts has been part of the problem, I think, but attitudes and
influences outside school is part, too.
> If you want to build a ship, don't drum up people to collect wood
> and don't assign them tasks and work. Rather, teach them to long
> for the endless immensity of the sea. -- Antoine de Saint-Exupery
> Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm