UM14 - Arduino based Step Sequencer

While making the SBE2 unit I realised that a great addition would be a step sequencer. So my definition of what I would like in such a unit started.

The UM14 is made to work with the SBE2 in mind. It has 4 independent 16 step sequence channels which can be linked together. Unlike most sequencers the output control voltage for each channel is limited to 3 voltages. These 3 voltages are still variable across the full CV range though. The reason behind this is that the sequencer is made for the SBE2 which is not a chromatically tuned machine.

I decided to make the brain inside the unit an Arduino since I have a better grasp of computer based circuits than an analog based one. This also allows for greater flexibility in operation later if needed.

Here's my definition of what it will initially do:

Here is the new definition:-

This is a CV and gate sequencer which has 4 independent channels to control the SBE2 synthesizer. The unit is not meant for 1v/oct units and only has 3 CV options per sequencer per channel. The front panel contains two sections - one is the sequence running controls and the other is where the steps of each sequence are controlled.

The step sequence section comprises a matrix of leds which is 4 high and 16 wide. There are three data encoders per row of buttons which set the three control voltage output options. The rows represent the individual sequences whereas the verticals represent the steps of the sequences. The leds will glow a colour relating to which of the three control voltages they output and whether their step will trigger the output or not.

The function of the RGB led is this. It will glow WHITE when its step is being played. When not being played it glow either RED, GREEN or  BLUE which is related to which of the three control voltages it will output when it is played. Whether a step has a triggered output or not will identified by the step led being brighter whereas a non-triggered output will be dim. The momentary button at the bottom of the step column will cycle through all the options as follows:- RED, RED triggered, GREEN, GREEN triggered, BLUE and BLUE triggered. To select to affect you must first press the select button to the right hand side of the row of leds.

The three control voltage knobs as mentioned are data encoders which unlike potentiometers are relative and not absolute. Using these allows for more options with regards to the computer for what range they may address.

To the left of each row of sequence leds are a knob, a pushbutton and led. The button is named SELECT. The SELECT button has several functions. The functions of this section are changed by pressing the SELECT button.

State 1:-
Led is YELLOW. This mode simply selects this Sequence to which the step buttons at the bottom of the columns will act on when selected.
State 2:-
Led is WHITE. This is the sequence length mode. This indicates that the SELECT data entry knob will change the length of this sequence between 2 to 16 steps. The Step  leds will glow WHITE starting from the left hand side and up to the step where the loop will start as of the next step.
State 3:-
Led is PURPLE. Now the data entry knob becomes a sequence DIVISOR. Now the step leds indicate the clock divisor. If only step 1 is lit then the divisor is 1 and if up to step leds 6 are glowing then the divisor is 6. This will allow up to 16 divisions to occur meaning that the master clock has to click over 16 times before the steps will change to the next one.
State 4:-
Led is ORANGE (or something similar). Now the data entry controls the step length of each individual step within the sequence. This represents the number of clock steps the currently selected step will stay for. In this mode the user selects the step by pressing the button at the base of the column of the step and by changing the VALUE control. This will increase or decrease the length. The length is represented by the 8 vertical leds on the left hand side of the panel and can range from 1 clock tick to 8 clock ticks.
State 5 - 7:-
Led is either RED, GREEN or BLUE. Now we are in set the CONTROL VOLTAGE modes. Here we set the output control voltage for 1 of the 3 options for this sequences steps. The led colour is related to that which can be selected on each step. By changing the VALUE control we change the output voltage for one of the three.
State 8:-
Led is PINK. Something that Catgirl synth man has on his sequencer is an option whereby if adjacent steps are on then the pulse is not reset so here would could have a case where normally a step pulse is half the length of the step and turn this option on and the pulse is only turned off when an off step is encountered.

We may change the order and colour of these options once the unit is in operation and accordingly with the ease of use.

The Clock knob will be a pot which controls the master clock rate. This master clock controls all four sequences unless an external clock pulse has been plugged into external clock inputs two to four. Clock input one is considered the master unless others are plugged into two to four as mentioned. I'm not currently sure how I would program this so it might not be available in the final project. There will also be a CV Clock input which is where a Control Voltage can be inputted that will control the speed of the MASTER clock based on a voltage.

On the left hand side is also the memory banks. Here will be 8 sets of memory buttons which represents 8 sets of the 4 banks of sequences plus all sequence based settings. Next to these will be a load and save button. To load a bank you simply press the load button which should make the leds above the bank buttons light up. Press the bank button to load the bank. They will light Green for a bank without a sequence and light Red for a bank with a sequence. If you load a bank without a sequence stored in the memory location then it will load a blank sequence. The same goes for saving a bank.

Three buttons sit to the far side of the sequence panel. As you can see they appear to link the sequences together which they do. When they are selected and the led is glowing then this means that the sequence above and below are linked which means that Sequence 1 now runs for 32 steps. And this will also continue on if the switch between Seq 2 and 3 and 4 is switched on. This example would make a 64 step sequence. The CV and Trigger outputs for the each sequence would then duplicate. So if Seq 1 and 2 were linked then the outputs of Seq 1 and 2 would be the same.

The RANDOM button will randomise Control Voltages, Step Length and Clock Divisor. These will affect the Sequence row that is currently selected. We could put in a UNDO button here as well.

There's a CV input which can control the speed of the sequence based on a CV. Some interesting effects could be generated by directing an LFO output to this input.

At this stage I'll plan to have more plugs on the input and output than needed in case I wish to add another function. This goes for control buttons. That way I will only need to change the labelling on the front panel.

Physical Connections: 8 input plugs which can be used for trigger pulses, control voltages whatever and 8 outputs which will be 4 triggers and 4 control voltages which relate to the 4 sequencers. I'll also put a MIDI IN and OUT which will possibly be another computer that will be both for timing to and from another sequencer and for triggering though I'm not sure I would assign the CV value - hmm actually that would be automatic as these would range across the normal MIDI note value. As I said this would be a third party board that takes care of these things.

Here's a picture of the current front panel design