Itty Bitty

Itty Bitty

A gate & CV sequencer that uses the binary representation of an 8-bit integer to determine the of/off pattern.

The module has 2 channels, A and B. Channel A is controlled by K1 and outputs on CV1-3. Channel B is controlled by K2 and outputs on CV4-6.

Inspired by an Instagram post by Schreibmaschine describing an idea for a new module.

Ins & Outs

• DIN: an input clock/gate/trigger signal used to advance the sequences
• AIN: optional CV control for sequence A and/or B (see configuration, below)
• K1: determines the value of sequence A: 0-255
• K2: determines the value of sequence B: 0-255
• B1: manually advance sequence A
• B2: manually advance sequence B
• CV1: trigger output of sequence A
• CV2: gate output of sequence A
• CV3: CV output of sequence A
• CV4: trigger output of sequence B
• CV5: gate output of sequence B
• CV6: CV output of sequence B

How the sequence works

The numbers 0-255 can be represented in binary in 8 bits:

• 0: 00000000
• 1: 00000001
• 2: 00000010
• 3: 00000011
• …
• 253: 11111101
• 254: 11111110
• 255: 11111111

Let 0 <= n <= 255 be the value the user selects with the knob. Every time we receive a clock signal we rotate the bits 1 place to the left, giving us n':

...
00000001
00000010
00000100
00001000
00010000
00100000
01000000
10000000
00000001
...

The “current bit` is the most-significant bit.

The trigger output will emit a trigger signal if the current 1s bit is 1, and no trigger if the current bit is 0. The duration of the trigger is the same as the incoming clock signal (or the duration of the button press).

The gate output will go high if the current bit is 1, and will go low if the current bit is 0.

The CV output set to MAX_OUTPUT_VOLTAGE * reverse(n') / 255. The bits are reversed so as to prevent a situation where the CV is always high when the active bit is also high; this forcibly de-couples the gate & CV outputs, which can lead to more interesting interactions between them.

Example sequence

Let’s assume sequence 83 is selected. 83 = 01010011

Step	Gate (High/Low)	Trigger (Y/N)	CV Out (10V max)
1	Low	N	7.921V
2	High	Y	3.961V
3	Low	N	6.980V
4	High	Y	3.490V
5	Low	N	6.745V
6	Low	N	3.723V
7	High	Y	1.686V
8	High	Y	5.843V

Time graph

Clock In
____      ____      ____      ____      ____      ____      ____      ____
    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |
    |____|    |____|    |____|    |____|    |____|    |____|    |____|    |____
         .         .         .         .         .         .         .
Gate Out .         .         .         .         .         .         .
         ._________.         ._________.         .         .____________________
         |         |         |         |         .         |         .
_________|         |_________|         |___________________|         .
         .         .         .         .         .         .         .
Trigger Out        .         .         .         .         .         .
         ._        .         ._        .         .         ._        ._
         | |       .         | |       .         .         | |       | |
_________| |_________________| |___________________________| |_______| |________
         .         .         .         .         .         .         .
CV Out (approx)    .         .         .         .         .         .
10V---   .         .         .         .         .         .         .
         .         .         .         .         .         .         .
_________.         .         .         .         .         .         .
         |         ._________.         ._________.         .         .
         |         |         |         |         |         .         .__________
5V----   |         |         |         |         |         .         |
         |_________|         |_________|         |_________.         |
         .         .         ,         .         .         |         |
         .         .         .         .         .         |_________|
         .         .         .         .         .         .         .
0V----   .         .         .         .         .         .         .

Configuration

This program has the following configuration options:

• USE_AIN_A: if true, channel A’s value is determined by AIN and k1 will act as an attenuator for the CV signal connected to AIN. Default: false
• USE_AIN_B: if true, channel B’s value is determined by AIN and k2 will act as an attenuator for the CV signal connected to AIN. Default: false
• USE_GRAY_ENCODING: if true, instead of traditional binary encoding, the pattern is encoded using gray encoding. This means that consecutive sequences will always differ by exactly 1 bit. Default: false

Decimal value	Traditional binary	Gray encoding
0	00000000	000000000
1	00000001	000000001
2	00000010	000000011
3	00000011	000000010
4	00000100	000000110
5	00000101	000000111
6	00000110	000000101
7	00000111	000000100
…	…	…

To enable Gray encoding, create/edit /config/IttyBitty.json to contain the following:

{
    "USE_GRAY_ENCODING": true
}