Allen organ project - proof of concept achieved. Facepalm.

Now that the LED control is integrated with the card reader, it's time to see if it actually can program a stop!

Open up the organ, and in it goes. Take the breadboard display terminal, select "Blockflöte 8'" and send it over.

WOOHOO! First try!

Try again - Octa-Bell. "Bing bong bing." Kinura. "Blaaaaat." Festival Trumpet. "ta-ta-ta-DAAAA!"

Time to close up the organ and work on suitable packaging for the terminal.

Oh dear. Oh dear. Oh [Nixonian expletive deleted].

The two rotary switches above the card reader leave absolutely no clearance behind the lamp strip.
There's no room for the rearward extension of the board.

Oh dear.

Fortunately, there's plenty of room underneath the card reader. Back to the bench.

I cut the card reader perfboard in half, and rewire everything so that I have two halves joined with a strip of ribbon cable. I'm a little worried about switching noise getting into the audio, so I try to control it some by having each LED have an independent ground return on an adjacent conductor. (Desolder all the LEDs and resistors. Solder in both ends of all 20 conductors of the ribbon cable. Replace the LED that I overheated in the rework process.)

After all this rework, Frankenreader goes back in the organ and looks like this:


From the rear. The logic board extends a little way under the reader.


From the top. The ribbon cable clears all the hardware above.

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Allen organ project - lighting the LEDs

Last time, I breadboarded the LED controller and got its serial communications working. Now it's time to fire those LED's.

When the controller is idle, all the LED's are on, as if there is no card in the slot. (Among other things, this convention allows me to continue programming the organ with cards, if I wish.)



Wow, those LED's are bright.

Now, let's look in detail at what happens when a card is inserted and removed.

[Update: I was wrong about the quadrature signal. The next post explains.]

• First, the paper blocks all the lamps (LEDs are all off). This condition persists until column 6 lines up with the photoresistors.
• Next, for each group of three columns, the row 9 hole, and the data in rows 0-6, come into view. LED 9 and the data byte are lit.
• The row 8 hole comes into view early, because its photocell is displaced half a column. LED 8 lights.
• The data column leaves the photocells (LEDs 0-6 and 9 go off).
• The timing column leaves the photocell (LED 8 goes off).
• About 1 1/2 column of blank space (all LEDs off) passes over, and then the cycle repeats for the next fifteen data bytes.

Once all this is done, the LEDs stay off for a short pause (the card blocks the light from all of them, andt then the entire cycle repeats, reversed in time, as the card is withdrawn. Finally, all the lamps are lit as the card exits the reader.

http://kbk.is-a-geek.net:2303/ci/41508259dd has the code baseline that does this. With the clock rate slowed down to where my human eyeball can track what's going on, the data look right.

Now to move the thing onto the card reader and try it out on the organ!

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