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# README
[STEPPER][stepper-itch] is a 16-step sequencer for the Game Boy Advance (GBA).
It features an intuitive workflow inspired by [Elektron instruments][elektron]
with per-trigger parametrization that allows access to the 4 DMG sound channels
in the console (2 square waves channels, 1 custom wave channel and 1 noise
channel). Supports 4 banks of 8 patterns that can be queued for live
performance.
### Controls
- D-Pad: Moves the cursor.
- Start: Start/Stop the sequence.
- Select: Context dependent mod key. Used for:
- Quick saving the current bank.
- Copy pasting.
- Adjusting notes by octaves.
- Adjusting bpm by multiples of 10.
- B: Toggles channels/triggers and play/pause/stop, switches banks and patterns.
- A: Hold it to adjust trigger parameters.
- L/R: Change trigger notes, parameter values, or BPM.
### Save/Load
STEPPER supports up to 4 banks of 8 patterns each. The current bank is saved by
switching banks or selecting the current one in the bank section. The banks are
saved to the SRAM and upon launching STEPPER the last saved state will be
loaded. Use "Select + Start" to quick save the current bank.
### Patterns
Patterns can be changed or edited by navigating to the left column with the
cursor. Pressing the B button will queue a pattern to run on the next cycle. The
queued pattern will be highlighted in blue. Only on pattern can be chained at
the moment.
We can edit different patterns other than the one that is currently playing. The
pattern we are currently editing is represented by a grey/blue cursor whilst the
one in play is highlighted in white.
Each pattern stores information about active channels and their trigger notes
and parameters. BPM can also be stored independently for each pattern.
### Note selection
Notes can be changed by pressing "L" or "R" over an active trigger. If the
cursor is on the channel selection mode, "L" and "R" will transpose all trigger
notes instead. Holding "Select" while adjusting notes will make it jump by an
octave instead of a semitone.
### Parameters
Channels 1 and 2 allow us to control the square wave duty cycle and envelope
(Initial volume, direction and time). Additionally, channel 1 can access the
"sweep" parameters, which when the time is not zero allows for some interesting
FX.
Channel 3 is the wave channel. In this channel we have access to 2 programmable
waves that can be edited manually or selected with 4 available presets (sine,
saw, square, random). The waves can be played independently (mode A or B) or one
after another (Mode A + B). This channel has no volume envelope thus a note will
keep playing until it encounters an active trigger with zero volume or
a different pitch.
Channel 4 is the noise channel, mostly used for percussive effects. It uses an
envelope to shape the sound and has two modes of operation. Mode A is more
rounder and mode B sounds more metallic.
Adjust the parameters by holding "A" hovering over a trig. Parameters are stored
per trigger and adjusted individually for each of them. If the cursor is on
channel selection mode, when adjusting the channel parameters these will be
copied to all 16 triggers. Note that this global adjustment is not stored when
saving banks and patterns. The grey color on the global adjustment helps
differentiate between trigs and channel parameters. A compatible trig/parameter
can be pasted into a channel to apply it to all triggers.
### Copy/Paste
The GBA has a limited set of controls but using STEPPER's contextual clipboard
we can greatly speedup the editing workflow. We can use "Select + B" (Copy) or
"Select + A" (Paste) to perform clipboard operations.
If the cursor is selecting a pattern, the entire pattern will be copied,
including active channels, triggers and parameters. Patterns can only be pasted
in other patterns.
Channels can be copied to other patterns or channels. If the paste destination
is a channel other than the original one, only the notes and active triggers
will be copied. If the channel is of the same type, all the parameters will also
carry over.
Copying a trigger transfer its pitch (note), active state (on/off) and its
parameter settings (Assuming the target is compatible, as explained above). If
we only want to copy the parameters, hold "A" to enter parameter select mode and
press "Select" to copy them. Now you can paste them to any compatible trigger.
Note that the clipboard doesn't currently transfer between banks due to the
platform's limitations.
### Using other gear and synchronization
Currently STEPPER has no MIDI sync but I've began research on implementing CV
gate out using the GBA's link cable. No ETA for this, since I'm missing a few
things to test my theories in hardware, but I'll keep you all posted. In the
future something like [ArduinoBoy][arduboy] could be implemented to provide this
functionality, but in the meantime STEPPER can work with other gear by manually
timing the playing head using a click/metronome or sampling patterns from
STEPPER to later arrange it into a full song in your DAW or sampler of choice.
The latter is my preferred approach.
Keep in mind that the BPM reported by STEPPER can be a bit off since it uses
whole integer values for timing adjustments, meaning that you may need to set up
your DAW/sampler to a fractional BPM value or use time stretching to get the
loops perfectly in time (For example 107 BPM in STEPPER and 107.6 on your DAW).
[arduboy]: https://github.com/trash80/Arduinoboy
[stepper-itch]: https://badd10de.itch.io/stepper-gba
[elektron]: https://www.elektron.se/en
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