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Improve responsiveness of Gates & Triggers (#364)
* Rewrite most of Gates & Triggers to reduce overhead in the ISRs, improve knob responsiveness * Don't invert ain; treat k2 as an attenuator, not an attenuverter. Add median filtering for additional debouncing * Minor cleanup * Add a section about fine-tuning short gates * Reduce samples when reading analogue inputs; the median filter de-noises enough that we can speed up sampling. Rename some variables for clarity * Add the formula used to calculate the gate duration * Move median(l) into a new experimental.math module, add mean(l) as well since they're both nice utility functions to have (even if mean() isn't used anywhere _yet_). Move some constants around, use MIN_GATE_DURATION_MS as the lower bound for the gate length, not TRIGGER_DURATION_MS * Move MedianAnalogInput into experimental.knobs * Expose the number of samples * median window size as parameters * Expand the class docstring * Linting
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‎software/contrib/gates_and_triggers.md

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@@ -13,19 +13,53 @@ rising/falling edge triggers.
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| `b1` | Manual input equivalent to `din` |
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| `b2` | Manual toggle input |
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| `k1` | Primary gate duration control |
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| `k2` | Attenuverter for CV input on `ain` |
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| `k2` | Attenuator for CV input on `ain` |
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| `cv1` | Gate output for `din`/`b1` |
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| `cv2` | Trigger output for the rising edge of `din`/`b1` |
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| `cv3` | Trigger output for the falling edge of `din`/`b1` |
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| `cv4` | Trigger output for the falling edge of `cv1` |
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| `cv5` | Toggle output; changes state on every incoming rising edge |
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| `cv6` | Trigger output for the falling edge of `cv5` |
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The gate output on `cv1` has a normal range of 10ms to 2s, depending on the position of `k1`. CV input to `ain` can
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increase this duration.
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Gate/trigger input on `din` should be at least 0.8V. Ideally the trigger duration should
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be at least 10ms, though shorter triggers may be usable.
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`ain` expects an input range of 0-10V. `k2` acts as an attenuverter for this input signal.
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`ain` expects an input range of 0-10V. `k2` acts as an attenuator for this input signal.
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The gate output on `cv1` has a range of 50ms to 1s, depending on the position of `k1`. The
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knob response is quadratic, giving finer precision at the higher (clockwise) end.
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When `ain` receives maximum voltage and `k2` is set to maximum gain, the duration of the gate on
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`cv1` is increased by 2 seconds, giving an absolute maximum gate duration of 3 seconds. The following
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formula gives the exact calculation of the gate duration:
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```
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k1 in range [0, 100]
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k2 in range [0, 1]
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ain in range [0, 1]
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MAX_GATE = 1s
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MIN_GATE = 50ms
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q(x) = (MAX_GATE - MIN_GATE) / 10 * sqrt(x) + MIN_GATE
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t = max(
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MIN_GATE,
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q(k1) + k2 * ain * 2s
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)
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```
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Gate time is rounded to the nearest millisecond.
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## Fine-tuning Gate Duration
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`k1` offers fairly coarse control over the gate length of `cv1`, especially at low values. If you need to fine-tune
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a gate duration in the 50-150ms range you should set `k1` to its minimum value and use a combination of a constant
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voltage into `ain` and a relatively low gain set on `k2`. By adjusting the value of your input voltage and turning `k2`
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you should be able to fine-tune the gate duration much more accurately.
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For example to accurately achieve 60ms gates, patch the output from an adjustable voltage source such as Intellijel's
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Quadratt (0-5V) or Molten Modular's Motion Meter (0-10V) into `ain`. Turn `k1` to its minimum setting and leave it
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there. Slowly increase `k2` and your voltage source while keeping an eye on EuroPi's display. When the display reads
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`Gate: 60ms` stop adjusting `k2` and the input voltage. While fiddly, this method will provide much finer control
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for short gate durations.
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## Timing Diagram
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@@ -36,39 +70,49 @@ minimum).
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```
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DIN or B1
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__________ __________
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________| |________| |______________
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B2
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__
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__________________________________________________| |
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. . . . .
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. . . . .
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CV1 . . . . .
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.______ . .__________________ .
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________| |____________| . |______
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. L1 . . . L2 . . .
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. . . . . . .
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CV2 . . . . . . .
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._ . . ._ . . .
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________| |_________________| |_______________________
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. . . . . . .
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. . . . . . .
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CV3 . . . . . . .
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. . ._ . ._ . .
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___________________| |_________________| |___________
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. . . . .
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CV4 . . . . .
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. ._ . ._ .
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_______________| |_____________________________| |___
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. . .
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CV5 . . .
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.___________________. .__
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________| |_____________________|
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.
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CV6 .
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._
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____________________________| |_______________________
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________| |________| |___________________
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. . . .
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B2 . . . .
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. . . . __ _
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__________________________________________________| |_| |_
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. . . . . .
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. . . . . .
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CV1 . . . . . .
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.______ . .__________________ . .
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________| |____________| . |____________
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. L1 . . . L2 . . . .
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. . . . . . . .
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CV2 . . . . . . . .
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._ . . ._ . . . .
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________| |_________________| |_____________________________
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.T . . .T . . . .
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. . . . . . . .
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CV3 . . . . . . . .
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. . ._ . ._ . . .
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___________________| |_________________| |_________________
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. . T . T . . .
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CV4 . . . . . .
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. ._ . ._ . .
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_______________| |_____________________________| |_________
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. T . T . .
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CV5 . . . .
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.___________________. .____.
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________| |_____________________| |___
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. .
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CV6 . .
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._ ._
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____________________________| |________________________| |_
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T T
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```
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We assume that between the first and second pulses, the combined CV input via `k1`, `k2`, and `ain` has changed,
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resulting in different gate lengths (`L1` and `L2`, above)
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resulting in different gate lengths (`L1` and `L2`, above). The trigger durations marked with `T` are 10ms.
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## Delayed Triggers
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If you need a delayed trigger, `cv4` can be used; set the gate duration of `cv1` to the desired delay
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duration. `cv4` will fire a 10ms trigger on the falling edge of `cv1`, which will correspond with the
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rising edge of `din` plus the delay. Note that using `cv4` in this way will limit the usefulness of `cv1`
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and `cv3`, as the gate length will be used to control the delay.
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There is no way to add a delay between the signal received from `din` or `b1` and the rising edge of the gate on `cv1`.

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