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Add Sigma script (#369)
* Initial commit. Docs mostly written, workflow planned out. Just need to write the darned thing now * Update the readme & menu * Add the voltage bins * Use lockable shift knobs, allow dynamic routing of ain. Implement the output voltage control (v1), add a simple debugging GUI. Script is finally being tested on live hardware * Implement spread calculations, add a new class to manage setting the output voltages at a desired time in the future * Update the docs * Revert to paired gate + CV outputs; this lets us coordinate triggers with CV changes. Fewer overall outputs, but this feels like a good trade-off for functionality * Remove the doc section about gate configuration * Linting * Be explicit about what knob modes we're setting in the b1 handler. Update the UI while scrolling through the bin modes * Update arp to use the new random_extras.shuffle function * Create experimental.bisect module, put bisect_left in that instead of in sigma.py * Modify bisect_left so it doesn't raise an exception and just silently clamps lo to zero if needed * Add the list of ain destinations to the i/o section * Typo * Forgot to save the file before committing previously * Add missing newline * Copy the entirety of bisect from the source; it's not that big and we might as well include all of it for convenience * Linting
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‎software/contrib/README.md

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<i>Author: [chrisib](https://github.com/chrisib)</i>
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<br><i>Labels: random, sequential switch</i>
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### Sigma \[ [documentation](/software/contrib/sigma.md) | [script](/software/contrib/sigma.py) \]
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Random CV, optionally quantized, voltages based on controllable normal distributions. Inspired by Magnetic Freak's Gaussian module.
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<i>Author: [chrisib](https://github.com/chrisib)</i>
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<br><i>Labels: random, quantizer</i>
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### Smooth Random Voltages \[ [script](/software/contrib/smooth_random_voltages.py) \]
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Random CV with adjustable slew rate, inspired by: https://youtu.be/tupkx3q7Dyw.
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‎software/contrib/arp.py

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from europi_script import EuroPiScript
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from experimental.quantizer import CommonScales, SEMITONE_LABELS, VOLTS_PER_OCTAVE, VOLTS_PER_SEMITONE, SEMITONES_PER_OCTAVE
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from experimental.random_extras import shuffle
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import random
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MODE_ASCENDING = 0
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MODE_DESCENDING = 1
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MODE_RANDOM = 2
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def shuffle(l):
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"""Shuffle a list randomly
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Replacement for random.shuffle, which doesn't exist in micropython
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@param l The list to shuffle
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"""
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for i in range(len(l)):
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n = random.randint(i, len(l)-1)
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tmp = l[i]
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l[i] = l[n]
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l[n] = tmp
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class Arpeggio:
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def __init__(self, scale, mode):

‎software/contrib/menu.py

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["RadioScanner", "contrib.radio_scanner.RadioScanner"],
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["Scope", "contrib.scope.Scope"],
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["Seq. Switch", "contrib.sequential_switch.SequentialSwitch"],
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["Sigma", "contrib.sigma.Sigma"],
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["Smooth Rnd Volts", "contrib.smooth_random_voltages.SmoothRandomVoltages"],
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["StrangeAttractor", "contrib.strange_attractor.StrangeAttractor"],
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["Traffic", "contrib.traffic.Traffic"],

‎software/contrib/sigma.md

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# Sigma -- Gaussian CV Generator
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This script is inspired by [Magnetic Freak's](https://magnetic-freak.com/) Gaussian module.
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Please see the [user manual](https://magnetic-freak.com/wp-content/uploads/2022/08/Gaussian_Eurorack_UserGuide.pdf)
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for details on the original module and a deeper dive into the mathematics used in this script.
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## Gaussian Distributions
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The Gaussian or Normal distribution is a bell-shaped curve often used in statistics. Unlike rolling a d20 in
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Dungeons and Dragons, where there is an equal chance of the roll being 1, 2, 3, ..., 19, or 20, a normal distribution
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is more likely to produce numbers in the middle of its range and less likely to produce numbers at the extremes. The
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way in which this probability changes is determined by the standard deviation of the curve, written using the
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Greek letter Sigma in statistics.
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## Inputs & Outputs
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Inputs:
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- `din`: an external clock signal to trigger sampling. The pulse width of this signal controls the output
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pulse width
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- `ain`: assignable CV control (can be disabled, or assigned to control `mean`, `standard deviation`, `jitter` or
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`bin mode`)
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- `b1`: shift button; hold to change `k1` and `k2` modes
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- `b2`: cycles through `ain` routing
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- `k1`: mean control / shift: jitter control
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- `k2`: spread control / shift: binning/quantizer mode select
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`k1` or `k2` will act as an attenuator for the assigned control (mean/spread/jitter/binning).
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Outputs are divided into 3 pairs: `cv1 & cv 4`, `cv2 & cv 5`, and `cv3 & cv 6`. `cv1-3` output gate signals
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with a duration equivalent to the duty cycle of the incoming clock on `din`. `cv4-6` output random control
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voltages according to the spread & mean controls and the binning mode.
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## Distrubution Control
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The following description assumes the binning mode is set to `continuous`.
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Changing `k1` will move the average output voltage of the outputs. Keeping the knob near-vertical will keep the
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averate output close to 5V.
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Increasing `k2` will increase the standard deviation of the outputs. At the lowest setting the outputs will be
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effectively locked to the mean set by `k1`. As `k2` increases the spread of output voltages increases.
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## Jitter Control
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By default all six output channels update simultaneously. By applying positive voltage to `ain` the outputs can be
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desynchronized, updating at random intervals. `cv1 & 4` will always trigger in-time with the clock on `din`,
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but the other pairs will trigger at normally-distributed intervals after `cv1`.
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## Binning and Quantize modes
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The CV outputs on can be configured to either oscillate between fixed voltage levels, output
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quantized 1V/Octave pitch levels, or a continuous smooth voltage.
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In Bin mode the output voltage will oscillate between values chosen from the levels below:
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| # Bins | CV Output Levels | Delta (V) |
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|--------|-----------------------------------------------------|-----------|
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| 2 | 0V, 10V | 10V |
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| 3 | 0V, 5V, 10V | 5V |
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| 6 | 0V, 2V, 4V, 6V, 8V, 10V | 2V |
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| 7 | 0V, 1.7V, 3.4V, 5V, 6.6V, 8.3V, 10V | 1.7V |
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| 9 | 0V, 1.25V, 2.5V, 3.75V, 5V, 6.25V, 7.5V, 8.75V, 10V | 1.25V |
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In Quantize mode, the output voltage will be quantized to 1V/Octave scales with the following resolution:
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| Quantize Mode | Delta (V) |
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|---------------|-----------|
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| Tone | 0.16667 |
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| Semitone | 0.08333 |
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| Quartertone | 0.41667 |
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| Continuous | inf`*` |
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Output will be in the range 0-10V
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`*` Not actually infinte, but as high-resolution as the DAC chips will allow

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