CLKr is an alternate firmware for the 2hp Clk module based on the core of Mutable Instruments' Grids. CLKr offers new, specialized functionality and an expanded featureset compared to the stock firmware shipped with Clk, while also offering a Legacy Mode that emulates the original functionality.
The inspiration for this alternate firmware came from my frustration using Clk to easily control other modules which expected high-precision clock signals of 24ppqn, such as Pamela's New Workout.
- A stable, proven internal clocking system based on Grids'
- A base BPM range of 20 to 240 (or even higher with control voltage)
- Analog CV control over the full BPM range.
- Pause button and gate input to halt the clock in its tracks (...or really just disable the output)
- Range switch now toggles between single-step output and adjustable multipliers
- Tap Tempo mode offers an alterate way to set your desired clock rate
- Settings menu lets you set the high-speed resolution and toggle the button between Pause and Tap Tempo functions
- OUT keeps blinking even when paused, letting you see how your CV is affecting the rate even without output (even in Legacy mode!)
- Select between 4ppqn, 8ppqn, and 24ppqn resolution for the high-rate output
- Tap Tempo and Settings are saved to memory, letting you pick up your patch right where you left off.
- Legacy mode can switch between linear and logarithmic scaling of the pot and input CV for increased control over high-rate clocks
In Pause mode, pressing will pause the output of the clock, and the bottom LED will be illuminated.
In Tap Tempo mode, pressing twice will set the clock to the beat of those taps, indicated by both LEDs blinking in synchrony. Tapping the button once more will unlock the clock.
Flipping this switch will swap between a low-rate output useful for driving step sequencers and a high-resolution mode perfect for controlling other clock systems.
20 to 240 BPM in Standard Mode.
10s to 3.4ms in Legacy Mode (depending on the range switch)
Frequencies ranging between 0.1 and 190 Hz.
Stops outputting the clock above 2.5v, starts it below 2.5v.
NOTE: This overrides the Pause Button, both pausing and unpausing.
Internally added (summed) to the value of the Rate control in software.
To enter the Settings edit mode, hold down the multifunction button (A) until the LEDs blink in an alternating pattern, and then release.
While in the Settings edit mode, both LEDs will "breathe" when waiting for an input.
To exit the Settings edit mode, hold the multifunction button down again.
While in the Settings mode, flip the Range switch (B). Left is the old Pause mode, and right is the new Tap Tempo mode. This is indicated by the top LED lighting for Pause, and the bottom LED lighting up for Tap Tempo mode.
In Legacy Mode, this changes the response curve of the pot and CV input. Left is linear response, right is logarithmic response.
While in the Settings mode, turn the rate knob. The current state is indicated by a combination of the LEDs
| Legacy | 4PPQ | 8PPQ | 24PPQ |
|---|---|---|---|
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I take no responsibility for the functionality or lack thereof of your module if you choose to follow this guide or install this firmware. DO THIS AT YOUR OWN RISK. You should not be doing this if you don't have experience with uploading firmware or using a terminal. I will not be giving support for installation or setup.
The board I used for development and testing has Rev8 on it next to the programming port. If you have a different board and aren't sure if this firmware will work on it, DON'T TRY UPLOADING. Instead, open an issue and attach a photo of your board and I'll let you know if it should work or not. I'll update this section as necessary to list known working board revisions.
You'll need a hardware programmer such as a USBtinyISP and either a set of AVR ISP pogo pins or 2x3 header pins to solder to the programming port on your Clk. (Please note that if you're on Windows you must install the libusb drivers before the programmer will show up correctly. Sparkfun has a good guide here)
You'll need to have PlatformIO installed, either as a standalone CLI program or as a plugin for code editors such as VSCode. For further information please see the PlatformIO docs.
Before doing anything else, backup what is already present.
AVRDUDE is installed by platformio and usually available in a location like C:\Users\[username]\.platformio\packages\tool-avrdude\avrdude.exe on Windows. On a Mac you can simply install avrdude with brew, or try to find platformio's installed copy. Linux users should investigate their respective package managers.
Connect your programmer to the board either by holding your pogo pin programmer against the ports (in the correct orientation!) or plug your programmer into your newly-soldered port. Power on the module using your eurorack power supply, and then run
$ avrdude -p m328p -P usb -c usbtiny -U flash:r:flash.bin:r
$ avrdude -p m328p -P usb -c usbtiny -U eeprom:r:eeprom.bin:rYou can restore to your stock firmware at any time from your backup using
$ avrdude -p m328p -P usb -c usbtiny -U flash:w:flash.binThere is also a copy of this file in this repository.
$ git clone --recursive https://github.com/stellar-aria/clkr
$ cd clkrConnect to the module as detailed in the Backup section, and run
$ pio run -t uploadYou may have to edit the platformio.ini file if you're using a different programmer than a USBtinyISP.
CPU: ATMega328P
Clock: External 20MHz Crystal Oscillator
PD5/OCC0B - Top LED
PD6/OCC0A - Bottom LED
PC4/ADC4 - Rate CV Input
PC3/ADC3 - Pause CV Input
PC2/ADC2 - Range Switch: HIGH Left, LOW Right
PC1/ADC1 - Rate Pot: 0v Slow, 5v Fast
PB5/SCK - Clock gate output
PB4/MISO - Pause Switch Input, not pullup
The two CV inputs and the Range switch pass through inverting unity-gain rail-to-rail op-amps, which which also acts to clamp any input voltages so they're safe for the MCU.
There's also info in the 2HPClk.txt file.
A huge thank you to Emilie Gillet, who transformed the Eurorack space with her work and who wrote the original Grids software.
CLKr is licensed under the GPLv3 license. For more details please check out the LICENSE file.
Grids' and avril's code is copyright (c)2011/2012 Emilie Gillet.
All other code is copyright (c)2023 Katherine Whitlock.
