Objectives

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Definitions: 

• Loop: a repeating musical figure. When we hit the end of a loop, it immediately starts playing again from the beginning
• Track: a unique place to record audio within a loop with level, pan controls 

Objectives Create an application for any available MCU Development Board, such as Arduino, Teensy, STM32F4-Discovery that satisfies the following requirements:

• Store and access an arbitrarily large number of loops
• Can play at least one loop at a time
• A loop can be comprised of at least 4 mono or two stereo tracks. (The maximum number of concurrent tracks in a loop may be limited by your processor choice)
• Can playback and record at the same time.
• Immediately upon ending the record state, the recorded track plays back in time.

Includes at least three of the following features:

• Time Stretching: change tempo without affective pitch of loop
• Pitch Shifting: change pitch or key of each track independently
• Loop trimming: Auto-trim a track to match start and end points of a loop, tracking and matching the BPM in use
• Reverse Play: set a track to play backward within a loop
• Overdub: Sets record mode. When in Overdub recording will be mixed with any existing material on a given track. Replace mode over-writes the content of a selected track.
• Slip: offset the start point of a given track or combination of selected tracks.
• Pan: control relative signal left and right 

Consider user-interaction. An audio looper is designed for playback and recording to happen concurrently. What controls and features make real-time recording and playback of loops very easy and straight forward? For example, how do you present punch in and punch out of recording as a loop is playing? 

Example Parts List: 

• Teensy USB board with pins: https://www.amazon.com/PJRC-Teensy-3-6-with-pins/dp/B01MG2PYYP/ref=sr_1_2?dchild=1&keywords=teensy+3.6+with+pins&qid=1600207500&sr=8-2
• Teensy 3 Audio Adapter Board: https://www.amazon.com/Audio-Adaptor-Board-Teensy-3-0/dp/B013V0ZK1E/ref=sr_1_3?dchild=1&keywords=teensy+3.6&qid=1600207431&sr=8-3
• Breadboard accessories (Note, this will include some things you don’t need, and the breadboard is pretty short, so you need a larger breadboard.) https://www.amazon.com/EL-CK-002-Electronic-Breadboard-Capacitor-Potentiometer/dp/B01ERP6WL4/ref=sr_1_5?dchild=1&keywords=LEDs+and+resistors&qid=1600208438&sr=8-5
• You will also likely need another large breadboard.
• San Disk Ultra memory card <= 32GB for the audio shield.
• Input Connection is sort of up to you: A nice mic preamp or a simple electret mic will do. Here’s such a mic that comes with a custom cut washer for the audio shield: https://www.pjrc.com/store/microphone.html
• Possibly also a 7-seg LED display for selecting files and setting numeric values?

Motivations

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Work with the ARM processor. Learn audio processing. Be awesome.

Qualifications

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Minimum Qualifications:

Beginner knowledge of electronics. Some experience with components, breadboarding and soldering. Maybe messed around with a Raspberry PI. That kind of thing.

Preferred Qualifications:
None Listed

Details

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Project Partner:

William Pfeil

NDA/IPA:

No Agreement Required

Number Groups:

1

Project Status:

Accepting Applicants

Website:
http://www.radie.us/literature/electrix/repeater/repeater_manual_BETA.pdf

Keywords:
Embedded SystemsIoTAudioARMEmbeddedlooping