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Finally Found My "Round To It" Part I #Homebrew

Rick
 

This is my first real post, so here it goes...

Back when I was a teen in the early 80’s, one of my dad’s co-workers gave me a stack of Popular Electronics magazines.  Shuffling through the stack, I came across the August 1976 edition that contained part one on how to build the COSMAC Elf.
  At the time, we didn’t have a home computer of any sort, so as an electronics hobbyist who wanted to learn microprocessors, I was super excited to build it.  In the early 80’s, it was quite hard for hobbyists to procure parts since the normal electronics vendors only wanted to deal with professionals.  Jameco and Digikey were my go to places, but they were just starting up.  To complicate matters, neither of them carried stock of the CDP1802.  My dad knew I wanted to build the Elf, so he took me to the Electronics Surplus store in Cleveland OH.  That place was like a candy store to an enthusiast like myself.  It is still in business today, and was a source of some of my parts.  If you ever need legacy parts, then give them a try as they have a mail order service.  Unfortunately at the time they didn’t have the CDP1802 either.  So I pretty much gave up since I couldn't find a CPU.

My career brought me thru the ranks of engineering, all the way up to a senior software engineer.  During that time, I stopped being a hobbyist since it was too much like work.  However, over the past two years, I ended up in program management, and no longer was engaged in what I really loved as a teen.  So I started to return my hobbyist roots.  That’s when I found that the CDP1802 has quite a following in the “maker” world.  Specifically Lee Hart’s 1802 Membership Card really tugged at my hearts desired to give the COSMAC Elf another try.  Good thing I kept all my old hobbyist supplies!  Some of my parts were really old, to the point where I had to clean the pins with an Exacto knife.  I only had one bad CD4013 and P2102 RAM. 

And my source of the CDP1802: The same Electronics Surplus store in Cleveland OH.  Funny how things come full circle!!!

Therefore, I build the original COSMAC ELF with some of my own mods using good old fashioned wire-wrap:
1) Used the original schematic as a starting point.
2) Had to have a Hex Keypad!  Ended up using a 74C922 decoder and a couple of flip flops.
3) Did absolute decoding on the N0-N2 signals for a multiple IO ports
4) Had to have the address displays
5) Most parts were 4000 series, but I cheated where practice (e.g. Bus buffers = HC245, bus latches = HC574).

The board pretty much worked the 1st time, and I had some fun entering the programs on a hex keypad instead of panel switches.  I've added some pics...

I continued to improve my CDP1802 computer by incorporating an assembler (A18) and Raspberry Pi loader (Yes!).  More on that later (Part II?)...





John
 

Very neat construction, Rick! (I wouldn't mind seeing the underside too).

I'm building a SC/MP machine using wire-wrap. I've lost my original SC/MP chip somewhere so I bought another from China. The same firm had 1802s at 99p each so I bought a couple of those. A COSMAC Elf will be my next project after the SC/MP is "finished" (i.e. further effort demonstrates the law of diminishing returns!)

Have you had those displays since the 80s, or did you find some at a reasonable price recently?

John, Nottingham, England

On Tue, 19 Mar 2019 at 02:08, Rick <rppolicy@...> wrote:
This is my first real post, so here it goes...

Back when I was a teen in the early 80’s, one of my dad’s co-workers gave me a stack of Popular Electronics magazines.  Shuffling through the stack, I came across the August 1976 edition that contained part one on how to build the COSMAC Elf.
  At the time, we didn’t have a home computer of any sort, so as an electronics hobbyist who wanted to learn microprocessors, I was super excited to build it.  In the early 80’s, it was quite hard for hobbyists to procure parts since the normal electronics vendors only wanted to deal with professionals.  Jameco and Digikey were my go to places, but they were just starting up.  To complicate matters, neither of them carried stock of the CDP1802.  My dad knew I wanted to build the Elf, so he took me to the Electronics Surplus store in Cleveland OH.  That place was like a candy store to an enthusiast like myself.  It is still in business today, and was a source of some of my parts.  If you ever need legacy parts, then give them a try as they have a mail order service.  Unfortunately at the time they didn’t have the CDP1802 either.  So I pretty much gave up since I couldn't find a CPU.

My career brought me thru the ranks of engineering, all the way up to a senior software engineer.  During that time, I stopped being a hobbyist since it was too much like work.  However, over the past two years, I ended up in program management, and no longer was engaged in what I really loved as a teen.  So I started to return my hobbyist roots.  That’s when I found that the CDP1802 has quite a following in the “maker” world.  Specifically Lee Hart’s 1802 Membership Card really tugged at my hearts desired to give the COSMAC Elf another try.  Good thing I kept all my old hobbyist supplies!  Some of my parts were really old, to the point where I had to clean the pins with an Exacto knife.  I only had one bad CD4013 and P2102 RAM. 

And my source of the CDP1802: The same Electronics Surplus store in Cleveland OH.  Funny how things come full circle!!!

Therefore, I build the original COSMAC ELF with some of my own mods using good old fashioned wire-wrap:
1) Used the original schematic as a starting point.
2) Had to have a Hex Keypad!  Ended up using a 74C922 decoder and a couple of flip flops.
3) Did absolute decoding on the N0-N2 signals for a multiple IO ports
4) Had to have the address displays
5) Most parts were 4000 series, but I cheated where practice (e.g. Bus buffers = HC245, bus latches = HC574).

The board pretty much worked the 1st time, and I had some fun entering the programs on a hex keypad instead of panel switches.  I've added some pics...

I continued to improve my CDP1802 computer by incorporating an assembler (A18) and Raspberry Pi loader (Yes!).  More on that later (Part II?)...





bill rowe
 

That's a nice clean build - your teen self would be pleased.


From: cosmacelf@groups.io <cosmacelf@groups.io> on behalf of Rick <rppolicy@...>
Sent: March 18, 2019 10:07 PM
To: cosmacelf@groups.io
Subject: [cosmacelf] Finally Found My "Round To It" Part I
 
This is my first real post, so here it goes...

Back when I was a teen in the early 80’s, one of my dad’s co-workers gave me a stack of Popular Electronics magazines.  Shuffling through the stack, I came across the August 1976 edition that contained part one on how to build the COSMAC Elf.
  At the time, we didn’t have a home computer of any sort, so as an electronics hobbyist who wanted to learn microprocessors, I was super excited to build it.  In the early 80’s, it was quite hard for hobbyists to procure parts since the normal electronics vendors only wanted to deal with professionals.  Jameco and Digikey were my go to places, but they were just starting up.  To complicate matters, neither of them carried stock of the CDP1802.  My dad knew I wanted to build the Elf, so he took me to the Electronics Surplus store in Cleveland OH.  That place was like a candy store to an enthusiast like myself.  It is still in business today, and was a source of some of my parts.  If you ever need legacy parts, then give them a try as they have a mail order service.  Unfortunately at the time they didn’t have the CDP1802 either.  So I pretty much gave up since I couldn't find a CPU.

My career brought me thru the ranks of engineering, all the way up to a senior software engineer.  During that time, I stopped being a hobbyist since it was too much like work.  However, over the past two years, I ended up in program management, and no longer was engaged in what I really loved as a teen.  So I started to return my hobbyist roots.  That’s when I found that the CDP1802 has quite a following in the “maker” world.  Specifically Lee Hart’s 1802 Membership Card really tugged at my hearts desired to give the COSMAC Elf another try.  Good thing I kept all my old hobbyist supplies!  Some of my parts were really old, to the point where I had to clean the pins with an Exacto knife.  I only had one bad CD4013 and P2102 RAM. 

And my source of the CDP1802: The same Electronics Surplus store in Cleveland OH.  Funny how things come full circle!!!

Therefore, I build the original COSMAC ELF with some of my own mods using good old fashioned wire-wrap:
1) Used the original schematic as a starting point.
2) Had to have a Hex Keypad!  Ended up using a 74C922 decoder and a couple of flip flops.
3) Did absolute decoding on the N0-N2 signals for a multiple IO ports
4) Had to have the address displays
5) Most parts were 4000 series, but I cheated where practice (e.g. Bus buffers = HC245, bus latches = HC574).

The board pretty much worked the 1st time, and I had some fun entering the programs on a hex keypad instead of panel switches.  I've added some pics...

I continued to improve my CDP1802 computer by incorporating an assembler (A18) and Raspberry Pi loader (Yes!).  More on that later (Part II?)...






--
Bill Rowe
Olduino - an arduino for the first of us
https://olduino.wordpress.com/about-2/about/

 

Greetings, John.  The time you spent on the parts placement, layout, and spacing was well spent.  It's beauteous.  Have you done up a schematic?

Cheerful regards, Mike

 

Pardon me.  I meant Rick...

John
 

I was just about to correct that, being the John in questions and being quite incapable of that quality of work!

John G4EDX Nottingham

On Tue, 19 Mar 2019 at 13:11, Mike McLaren, K8LH <k8lh@...> wrote:
Pardon me.  I meant Rick...

Timothy Stoddard
 
Edited

Outstanding work! Have you tried David Madole's bootloader? It has worked really well for me to upload BIN files via serial interface comprised of Q and EF3. I was able to load up his version of figForth with his 24 byte bootloader. Here's my SBC1802 running the bootloader and figForth: https://youtu.be/4QIvP3SKYZA

--
Tim Stoddard
"Life with technology: It's a roller coaster ride!"

Rick
 

Thanks for the complement.  My construction skills came from starting out as an Electronic Tech years ago.

I found the displays at Amazon for about $12 ea, but they are no longer available.  I picked up some on eBay a few weeks ago ($5ish each):
https://www.ebay.com/itm/Closeout-discounts-on-TIL311-DIS1417-Hexadecimal-Smart-Displays-with-logic/302740853622?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Have not had a chance to test them, but they are in impeccable shape and the vendor packaged them very well.  Even better than digikey and mouser if you can imagine that.

Rick
 

Here's the schematics for the user keypad and the main boards...

Note: I've made a few mods that are not in the above photos.  I had to add more connectors for memory expansion, and an experimenter circuit.

Jeff Truck
 

Thanks Rick!

Jeff

On Tue, Mar 19, 2019 at 8:35 PM Rick <rppolicy@...> wrote:
Here's the schematics for the user keypad and the main boards...

Note: I've made a few mods that are not in the above photos.  I had to add more connectors for memory expansion, and an experimenter circuit.

Gregg Levine
 

Hello!
Rick, what style display are you describing? Technically the Hex
displays that were originally an HP product are still with us, they
are now part of the Broadcom line of (mismanaged) managed components
division. They are actually considered to be replacements for the
famous TI designs.

One off topic remark, one thing I do like about this group service is
the lack of the advertisement below the message that they consider to
be a footer.
-----
Gregg C Levine gregg.drwho8@...
"This signature fought the Time Wars, time and again."

On Tue, Mar 19, 2019 at 5:37 PM Rick <rppolicy@...> wrote:

Thanks for the complement. My construction skills came from starting out as an Electronic Tech years ago.

I found the displays at Amazon for about $12 ea, but they are no longer available. I picked up some on eBay a few weeks ago ($5ish each):
https://www.ebay.com/itm/Closeout-discounts-on-TIL311-DIS1417-Hexadecimal-Smart-Displays-with-logic/302740853622?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Have not had a chance to test them, but they are in impeccable shape and the vendor packaged them very well. Even better than digikey and mouser if you can imagine that.

Rick
 

The displays that I used were TIL-311 displays.  I had two HP 5082-7340s that I collected as a teen, but one of them was damaged.  Therefore, I had to buy the 311s from Amazon.

The parts that I received from the link I provided were DIS1417s...