Summer RetroChallenge 2012
My entry for the summer RetroChallenge 2012 are two projects:

1. Build the 1802 Membership Card I just bought and learn to write some code for it. If time permits, I have a surprise steam punk twist planned for this little computer :)

2. if my Atari 800 ships in time, I will do a video of it reading a rather unusual storage medium.

Last updated: 2012-JUL-30 <- Click for the latest!

Frist Post! 2012-JUL-03
The first order of the day is to decide in what order to run this "blog". Newest entry first seems popular, but I want this readable for newcommers as well, so oldest first it is!

Click the date above, it is a shortcut to the latest post.

Now, I must come clean. I started already in June. I'm actually almost done soldering the 1802 Membership Card. I'll portion out the build log to keep it exciting.

Kit recieved! 2012-JUL-03
Woohoo, the 1802 Membership Card is here! It comes in nice minty tin box: (all pictures are clickable!)

Altoids tin

The content was pretty tightly packed, it was a little fiddly getting the circuits boards out.

Altoids tin open

Here is everything except the three boards, not much is needed to make a computer.


Now I just need to find the soldering iron :/

Soldering begins 2012-JUL-04
Finding the soldering iron was more work than expected. I just moved house and the iron, solder and other tools were in three different boxes.

But here are the first components in place:

Board with a few components

Just ordinary through-the-hole components. The CPU and RAM requires a special mention. In order to reduce the height of the overall card the two big ICs are not mounted in sockets but in small "socket pins". You thread them onto the bare pins of the IC, mount the IC (and pins) on the circuit board and solder the pins in place. Now the IC is removable!

Here are the pins on the CPU: CPU with socket pins

Now I got some more soldering to do :)

Almost there! 2012-JUL-05
There, all parts in place, save two switches. The instructions warns you to be careful with the switches. Yet, I managed to break two of them when I was figuring out whether the nuts could be used as an end stop for the cover panel (they can, and I recommend it).

Overall this is a great kit, getting the LEDs, switches and the DSUB connector in the right place was the trickiest part, but made simpler by using the cover panel as a guide. My only real complaint is that the order the build instructions suggest you mount the components isn't the best. In particular I would solder the R11, R12 and R13 SIP resistors in place before the DSUB, LEDs and switches. Almost complete board

Here are the two logic boards stacked together. Quite a close shave, I will have to trim the jumper pins a bit. Notice how the DSUB is mounted at a distance from the board. I did this so I can mount the cover board flush against the DSUB. I put half a wooden clothes pin as a distance and pressed the boards gently together with a small vice while soldering.

Two boards together

Luckily the swithes are cheap and in stock at elektro:kit, so I have two on order which should arrive tomorrow :) Just in time for another update.

Two spares and one headache later! 2012-JUL-12
The spare switches arrived quickly and put in place so that I could start toggle in some programs from Tom Pittmans excellent guide from 1980: A "Short Course In Programming". Program 2.1, 2.2, 2.3 worked like a charm, so did 3.1 through 3.7, but uh-oh 3.8 is acting real weird:
         ..  PROGRAM 3.8 -- TEST OUT
0000 64          OUT 4   ..
0001 00                  .. (DATA TO BE OUTPUT)
0002 3F          BN4 0   .. LOOP BACK
0003 00
0004 64          OUT 4   ..
0005 11                  .. (DATA TO BE OUTPUT)
0006 30          BR  2   .. LOOP BACK
0007 02
This code loops between 00 where the LEDs are set to zero and 02 where the status of the IN button is polled. If the button is up the loop continues (branch to 0), if it is down the program continues to 04 where the status LEDs are set to 11 and will then loop between 02 and 06.

In other words, when IN is pressed the LEDs will show one bit pattern and when released it will return to the initial blank pattern.

However, when I release the IN button, the "11" pattern would sometimes remain, and sometimes turn into a completely different pattern. I can examine the program in memory and it is perfectly fine... what is going on!?

After exchanging a mail with Lee Hart I could figure it out. When I soldered resistor R3 and diode D9 I accidentaly bridged two pins. In an effort to correct this I damaged the CPU board leaving the connection between R3 and D9 open. I simply restored the bridge with a dab of solder and the board works perfectly!

Membership Card showing it's blinkenlights

I must say this is a great kit, all problems has been my own fault and I've learned some lessons. What's next? Well, there is that steam punk twist I promised, I think there is enough time for it. Then there will be a video for you :)

In the meantime I'm hoping my Atari 800 will arrive.

Running out of steam.2012-JUL-30
Finally, on the last day of the retro challenge, I have time to realise the steam punk twist ending! But I'm afraid I must report that it has been a failure :-(

The 1802 runs on very little current, so it would be cool to power it with another "toy": My D10 steam engine from Wilesco!

Step one was to dig out the D10 from the my parents attic. It worked like a charm! Next I had to find a generator. Luckily my friend has the M66 Dynamo. We did some tests with his larger D20 engine and it output about 5-6 V at a (fairly) steady level.

The idea is to program the 1802, turn off the clock and swap the batterypack for the generator output. The membership card has a capacitor that can keep the memory going for a few minutes.

I quickly realised that my D10 wasn't up to the task. Once steam pressure was built up and the flywheel set in motion I got a pretty good power output, but pressure dropped quickly. I am not convinced that the computer ever ran on anything other charge stored in its capacitor. I could test with my friends D20, but he is out of town.

At least I can give you a picture of the setup: Computer Name

And with that I say thank you for reading all the way down here, Retro challenge has been a lot of fun! Perhaps I'll see you next time.

Oh, And the Atari never arrived, perhaps that project can be my entry next time.