ABOUT
We want someone to be able to walk up to the board, tap in a few notes, twist a few knobs, and instantly feel the joy of crafting their own music.
Orris is wall-mounted synth rack driven by a sequencer, which acts as the brain of the system. The sequencer triggers user-inputted notes to connected synth modules. The modules can be either synthesizers or effects modules, all controlled digitally but output analog signals. Each synth or effects module plugs into a backplane that routes analog signals to a mixer and enables inter-module audio routing via a connection matrix. In this version, the mixer simply combines the various audio signals and drives the speakers. The entire system is powered by rechargeable batteries or via USB through the power supply block. Mechanically it is equivalent in dimensions and weight to a medium-to-large sized picture frame.
REQUIREMENTS
High-level Requirements:
The user can enter steps by pressing the sequencer’s buttons, which are arranged in a 4/4 time signature across four separate bars. As the sequencer runs, it sends signals to the connected synthesizers, prompting them to play the notes programmed into each step.
There shall be six available slots for user-swappable modules. Modules may function as either synthesizers or effects units and will be able to communicate with the sequencer. Each module will include at least one analog audio output and will have the capability to receive audio input from any of the other modules via the backplane.
For the initial revision, the mixer will simply combine the audio signals from all modules and output the result through a built-in speaker.
Nice to Haves:
Users can also modify the pitch of each step to create custom melodies or patterns.
The system shall be battery powered and capable of running for a minimum of three hours on a full charge. It can also be powered and recharged via USB.
Removed idea of having this system battery powered. Rechargeable batteries are a bit of an expensive hassle and the additional complexity it adds to the project is not worth it.Mechanically should be equivalent in dimensions and weight to a medium-to-large sized picture frame.
THE SYSTEM
A first draft of the system block diagram is shown below.
The sequencer is primarily composed of a microcontroller along with buttons, LEDs, and seven-segment displays forming the user interface. Special attention will be given to how the sequencer manages these inputs and outputs. Depending on the chosen microcontroller, buttons and LEDs may be driven directly or through I/O expanders. Each seven-segment display contains 7 individual LEDs, making them somewhat cumbersome to control via I/O expanders or directly from the microcontroller. A more efficient approach will be to drive them using shift registers - assuming rapid updates aren't necessary, which is currently not expected.
The power supply includes a USB-C connector with a USB Power Delivery (PD) controller to allow for increased current and voltage over USB. Power will be provided by 18650 lithium-ion batteries rated at approximately 2500 mAh each. The configuration will be either 2S or 2S2P (two cells in series and optionally two in parallel) depending on the final capacity requirements. Battery management will include protection circuitry, cell balancing, and basic monitoring - likely by measuring overall battery voltage. At this stage, it is yet to be determined whether voltage regulators will be part of the power supply block or distributed across individual modules. Removed idea of having this system battery powered. Rechargeable batteries are a bit of an expensive hassle and the additional complexity it adds to the project is not worth it.
The backplane serves as the interconnection point for the modules and carries shared signals. It will distribute power and ground, UART_TX (for communication from the sequencer), a CLICK signal (for synchronization), and the analog audio outputs from the modules.
Each module will include a microcontroller to receive step data from the sequencer. Modules may also be capable of selecting and routing audio from other modules, particularly in the case of effects units. The remaining module circuitry will handle synthesis or audio processing.
Finally, the mixer will combine the output signals from all modules in a 1:1 mix (for now) and drive the built-in speaker.
