Settings view

Change global settings, such as UI color and display orientation, change quantizer scale or save/load global presets.

Settings: Move right knob to select an object in the list, push right knob to toggle on/off.

Scales

The frequency of the phase progression and the static voltage output can be quantized to fixed values according to .scl files loaded onto the device using the USB port between the knobs.

To enable a specific scale, push the left knob once to enter the settings view and rotate it until you reach the SCALES sub page. Then use the right knob to select a scale from the list. The list of scales is updated on boot according to the content of the /scales directory.

If a .scl file cannot be parsed, it will simply not appear in the list. Please ensure that the formatting of the .scl files follows common practices.

There are many existing scales to try out here:

Scala Library

Or you can create your own using an online scale editor

Scaleworkshop

The quantizer “locks” to the nearest value in the scale, and requires the incoming voltage to change a bit before it locks onto another value. This is to prevent “quantizer chatter” where minor fluctuations in voltage causes the frequency to oscillate between two values in the scale. The concept itself is called hysteresis, but it just means there is a dead zone between the notes in the scale where small changes do not affect the output.

You can change what the quantizer applies to in the settings view.

Sync

The sync input jack detects the rising edge of square waves and has a few different behaviours you can turn on or off:

Looping

If the phase should pause or not after playthrough. If off, a sync input pulse unpauses the phase.

Reset phase

when a trigger or gate is detected on the sync input, the phase progression is reset to 0(time starts over).

Tap Tempo

when a trigger or gate is detected on the sync input, or the (center) reset button is tapped, the time passed since the last incoming sync signal is calculated and the frequency of the phase is matched to this interval.

Enabling tap tempo also enables clock multiplication and division in place of the frequency setting.

Step

1v/oct output jumps to the next node X position every time the phase loops, much like a step sequencer.

Ext. Clock

Detach the step sequencer from the main phase and clock it externally using the sync input. The phase progression of the spline output is then running at a different rate than the 1v/oct output, which only changes when a pulse is detected on the sync input.

Sample & Hold

Samples the 1v/oct input at the time of an incoming sync signal. The sampled value is then optionally quantized and output to the 1v/oct output jack.

Presets

Save, load, update or rename presets.

By pushing the right knob when Create preset is highlighted, you can save the current settings for later recollection.

When you push the right knob the screen will change to a naming interface where left knob changes the cursor position and the right knob changes the letter. Push the right knob again to save, push the left knob to cancel.

The saved name will always appear in the UI color selected in the System settings menu.

Selecting an existing preset and pushing the right knob will open the options for that preset, which include load, rename, update and delete. If you load the preset, your current settings will then be overwritten and will not be retrievable unless you saved them first. If you have made changes and wish to update the preset, you can choose update and your current settings will be written to this preset. Rename opens the naming interface and saves the same preset with a new name. Deleting the preset will require additional confirmation.

Loading the factory settings purges the persistent memory and zeros the settings to default values. This might be useful in case of corrupted memory or other problems with the device.

The preset file contains all the current settings and can be copied to other Splines modules or backed up to your computer.

UI color

Select the primary color for the UI.

The active color is also used to differentiate the list of presets when they are saved.

Settings

These are additional settings that don't gracefully fit into the main UI layout. I have decided to let users turn them on or off independently of one another, even though some of the settings may override/interfere with others, but since they still produce interesting results, I leave it up to you to experiment.

Quantize frequency

Whether or not the quantizer applies to the phase frequency.

Quantize voltages

Whether or not the quantizer applies to output voltages.

Forward 1v/oct

When active, the 1v/oct output will only output the incoming signal at 1v/oct input, optionally quantized, so that you can use the quantizer independently of the spline output.

Transpose nodes

Turn on or off if the node Y positions are affected by 1v/oct input signals.

TCB expander

Turn on or off the expansion module. This module is not yet in production, but will add two more CV inputs for scroll and zoom, and potentiometers for the most important parameters, for more tactile control. Leaving it off ensures that the extra CV inputs do not accidentally affect the scroll and zoom values.

Time unit

Change from Hz to milliseconds.

Bright display

Increased display brightness for sunny days.

Flip display

This setting flips the display upside down and inverts the left/right function of the buttons.

Endless menus

If menus should loop at the ends or not.

Firmware

Displays the firmware version installed, so you can see if you need an update or not, or for debugging purposes.

How do I...

- use it as a step sequencer.

To use the module as a simple step sequencer, change the Sync mode to "step" and patch in a gate or trigger source to the Sync input. The phase progression will be paused and it will jump right from one node to the next every time a pulse is detected.

You can continually transpose the entire sequence without affecting the frequency by going to settings and enabling "Transpose Nodes", then patching a transposition signal to the 1v/oct input.

- externally clock the steps.

Go to Settings and activate both Ext. Clock and Step. The module will then use the sync input pulses to progress the step sequencer instead of the internal phase reset. The spline output then runs on the internal clock separately.

- use it as an LFO.

The normal LFO mode is simply the same as the VCO mode but at a slower phase frequency setting.

You can also change the Sync setting to "tap tempo" which will make the phase frequency match the time interval between incoming pulses on the Gate input and enables the clock multiplier/divider feature. You can also tap the center button(reset) to tap out an interval.

- externally sync the LFO.

If you enable Tap Tempo, the frequency will be automatically adjusted to match the period of the incoming pulses on the sync input or the taps on the center button(reset). You can then use the right knob to set clock division and multiplication.

- use it as an envelope generator.

By turning off Looping in the Sync view, you can use the module as a complex envelope generator. The phase will now pause at the end and will hold for a sync input pulse. Turn on Reset phase in the Sync view to allow for mid-phase retriggers.

You can set the timing units to milliseconds in the Settings page if you prefer that.

- select and edit multiple nodes.

Hold down the pause button(rightmost button) while turning the right knob. This will select neighboring nodes as well. Release the button to adjust the value for all the nodes at the same time. Their values will be adjusted from their individual starting points, so their relative difference in settings will remain. Using the reset button(middle button) instead will select every other neighboring node.

- alter the quantizer scales.

You can change the scales by connecting a USB C data cable to the module and holding the right knob down on boot. The module will then appear on your computer as "SPLINES". Inside there are three directories, one of which is called "scales" and contains the quantizer scales. The church modes are part of the firmware, but the other scales in this folder can be deleted, edited or replaced. Just ensure that the formatting of the files is consistent with the .scl file format conventions.

- make a backup.

Connect to the module using a USB C data cable and restart while holding the right knob down. Copy all of the content from the SPLINES drive to your computer for safekeeping.

- move your presets to another unit.

Connect to the module using a USB C data cable and restart while holding the right knob down. Copy the presets and scales directories from the SPLINES drive to your computer, repeat process in reverse with another unit. Do NOT copy the calibration.txt file to another device, as this file is unique to each device. If you do this by accident, simply delete the calibration.txt file and it will be recreated from internally stored factory calibration data.

- update the firmware.

Connect to the module using a USB C data cable and restart while holding the right knob down. Download the new firmware file from this site, and place it in the firmware directory on the SPLINES drive. Then eject and restart the module and you will be prompted if you want to update the firmware. Push the right knob to proceed.

- reset to default values.

Go to the presets list and load the factory settings in grey at the bottom of the list. This will zero all of the persistent memory settings and load default values.

- calibrate the inputs/outputs.

The module comes with a step by step calibration process.

You first need a precise multimeter. Then go to the CV Scope view(any page), and push both the center (Reset) and right (Pause) buttons at the same time. This will start the calibration process. Instructions will appear on screen, but the process is as follows;

1. Calibrate the spline output using your multimeter and the right knob
2. Push the rightmost button(pause) to confirm the calibration
3. Patch the spline output into the level cv input
4. Push the rightmost button(pause) to calibrate the input
5. Repeat for each other input
6. As the last step, calibrate the 1v/oct output using your multimeter as you did the spline output, then push the pause button again to finish the calibration

The calibration data is stored in two places, on the persistent memory module and in flash memory on the USB partition as a calibration.txt file. You can edit this file manually over USB, and it will overrule the stored calibration. If you delete this file, it will be recreated using the internally stored values. This is a backup feature to prevent accidental loss of the calibration.

More conveniently, you can also adjust calibration using the CV scope's per-channel gain and offset settings, but these settings will be reset if a preset is loaded!

Downloads.

Release firmware v1.0.0

Factory presets

The included presets are as follows:

• Blank Pattern.spl: A blank start with neutral settings.
• Envelope Bounce.spl: Using rectify clipping to create a bouncing voltage that plays once.
• Envelope.spl: Approximating a normal envelope shape using node positions. Looping turned off.
• LFO Tap Tempo.spl: Tap tempo on, frequency 1Hz
• LFO.spl: Tap tempo off, frequency 1Hz
• Quantizer SH.spl: Samples the 1v/oct input on sync pulses, quantizes it and outputs it on 1v/oct out.
• Step Seq Extern.spl: Externally clocked step sequencer mode, with independent spline output
• Step Seq Intern.spl: Internally clocked step sequencer mode
• VCO Fold.spl: More complex VCO approximation with wavefolding active
• VCO Saw.spl: Classic saw waveform output
• VCO Sine 4 Bit.spl: Bitcrushed sine waveform output
• VCO Sine.spl: Classic sine waveform output
• VCO Square.spl: Classic square waveform output
• VCO Triangle.spl: Classic triangle waveform output

Factory scales

The "church modes" are part of the firmware, but all the other scales are .scl files on the USB drive partition which can be deleted or edited. I have selected some scales from the scala library that I found interesting, but there isn't much more thought put into the example scales included with the device.

The scales in the .zip file are as follows, with their included comment:

• Arabic zanjaran on c.scl: Arabic Zanjaran with perde rast on C by Dr. Oz.
• Blues.scl: 6-note blues scale with flat 5th
• Bohlen pierce.scl: See Bohlen, H. 13-Tonstufen in der Duodezime, Acustica 39: 76-86 (1978)
• Hindustani.scl: North Indian Gamut, modern Hindustani gamut out of 22 or more shrutis
• Iranian pentachord 7-limit.scl: Iranian pentachord 42:45:48:56:63
• Lebanon.scl: Lebanese scale. Dastgah Shur
• Stellarhex.scl: Mandala/stelhex/cube(2) plus 7/6 and 7/5; convex in marvel tempering

There are many more existing scales to try out here:

Scala Library

Or you can create your own using an online scale editor

Scaleworkshop

Developer resources.

Since the format and architecture of the module lends itself to many other potential uses, I have created some developer resources that will help you get started with making your own firmware for it.

The hardware specs are as follows;

• 1.83" 284 x 240 full color ST7789P LCD over SPI
• ESP32-S3 WROOM 1U N8R8 with wifi and low power bluetooth
• PCM5102 32-bit 384kHz stereo DAC over I2S
• MCP3208 8-channel 12-bit ADC up to 100 ksps over SPI
• FM25V10 FE-RAM 1 mbit persistent memory module over SPI
• Breakout connectors for all ADC channels and i2c are provided for expansion modules as well.

Templates, drivers, pin configurations and basic instructions can be found in this github repository: splines_templates