Next in the sequence

The switched multiple’s record for largest number of panel components didn’t stand long. This new module has, if I’ve counted correctly, 59 panel components. Then again, it’s a bit bigger than the switched multiple.

20 by 40 cm. It’s an 8 Step Keyboard Sequencer, my variant of the LMNC version. Sam Battle designed a digitally controlled analog sequencer with eight steps, two CV outs. An Arduino Nano does the heavy lifting, which means unlike for instance a Baby 8 it can do things like run the sequence backward. There are switches that let you step the sequence manually, either direction. There also are arcade buttons that let you play it like a keyboard, generating CVs and a gate with each button push.

My version makes a number of changes of varying importance and obviousness:

  • There’s an eleven position rotary switch. The first seven positions let you choose a sequence length from 2 to 8. (No, you can’t choose a sequence of length 1. Come on.) The remaining four let you choose various patterns for playing all eight steps: inclusive or exclusive up-and-down, two of each step, or random order.
  • There are eight toggle switches that let you disable output for each step. (Note that if you’re driving an oscillator with this, turning off a switch doesn’t make the oscillator go silent… oscillators don’t go silent! It just makes the oscillator play whatever note it plays with 0V input. You’d need to do something like use CV2 to gate an envelope generator to get a sequence with silent steps in it.)
  • There’s a Zero gate input corresponding to the Zero toggle switch position (which turns off all steps).
  • There’s a “Reverse Time” toggle switch. Flip it up and the functions of the Forward and Backward gate inputs are interchanged. So if a clock is sent into the Forward input, and you flip Reverse Time, the sequencer starts stepping backward.
  • Internally: There’s a 5V external regulator, and it’s connected to the Nano’s 5V pin, not the VIN pin. The latter’s not the correct way to do it. Also, there are Schottky diodes to ground on each CV input. (But none to VCC. I had those in the design at one point, and then decided to take them out, but I can’t remember my reasoning. Well, they’d’ve made either the stripboard or the panel wiring more complicated, and the Arduino does have protection diodes.)
  • The code’s more or less a complete rewrite, to support the hardware changes, conform to my preferred coding style, and implement switch debouncing.

This was a strange build, because very little is on the stripboard.

Those four Schottkys are under the Nano. Aside from them, all the resistors and diodes in the circuit are soldered directly to panel components, which are connected with a confounding maze of wires to each other and the stripboard.

How many boneheaded wiring errors can you make doing something like this? Nope. More than that. For one thing, did you know when you look at the back of this thing, the steps go from 8 to 1 left to right instead of 1 to 8? It’s true. That was partly fixable in software, but in this version the step 1 button is special because it connects to the same pin as the Reset switch instead of its own Button pin, so buttons 1 and 8 did have to have their wires exchanged. Then there were the eleven toggles, of which I got three right and the other eight wrong: off was up and on was down. I refused to live with that, so I had to rewire all eight.

The panel graphics, well, tell you about that another time.

It’s done, it’s debugged — well, I don’t know of any remaining bugs. Schematic and code are on my GitHub.

One thought on “Next in the sequence

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