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uRockMusic On MCU
by Sonicyang Anarchih KK Hirokiht
Outline● Project Target● Circuit Design● How community helped us● How Effect works and Implementation● Wav Playing and Recoder● UI● Challanges & Obstacles● Housing
Project Target - InspirationAt the beginning, we want to try out audio signal processing on microcontrollers, insteads of traditional method, DSPs.
As we are Guitar players, the Product we choose is Guitar Effect Pedal.
What is Effect Pedal
Circuit DesignOn our Design we want most of the work done digitally.
The analog Circuit mainly contains some amplifiers and voltage regulators only.
Amplifiers and Level Shifters
Voltages RegulatorsThe on board Switching regulators are noisy, thus we use external voltage regulators.
● We are using TI’s TPS7A4700, RF Rating
Through, QFN20 is hard to solder,the result is Outstanding.
How Communities helped us
Libraries and Firmware we are using● STM32 Cube● FATFS● uGFX● ARM DSP Lib
OSS and sharing have make our way to the goal much more easier
STM32 Cube
New HAL Firmware means fewer bugs.Handy STM32 Cube MX software, Generate Hardware related Initializing code.
Comes with multiple Middlewares.● FreeRTOS● FATFS
uGFX
Ported to base on Cube Firmware and FreeRTOS
Very Flexible and portable, eased our pain on UI designing.
ARM DSP Lib
Utiliztiing ARM’s SIMD instructions to speed up signal processing.
support Fix point and floating point, but SIMD is only available to fix point numbers.
Effect
● Distortion● Overdrive● Equalizer● Compressor● Delay● Reverb
For coding the effects, we use the ARM DSP Library to help us.
We also use Q12 numbers(fix points) to enable the possibility to use ARM Cortex-M4F DSP & SIMD
By using the Above 2 technicals, the speed gain is LARGE.
Aid of Python and MATLAB
To simulate the Effects and visualize before hands. we use python and MATLAB to test the algorithms.
Effect - Overdrive & Distortion
Effect - Compressor
Effect - Delay
The internal SRAM is not deep enough, thus we store the delay data on external SDRAM.
Effect - Equalizer
Use IIR Filter to filter the audio.Coefficient designing base on MATLAB’s aid.
Wav Player and Recorder
Implemented Wav player and Recoder which plays 16bits 44100k files
The purpose is to let user recode clips to accompany himself playings
UI
Challange & Obstacles
1. HAL Firmware is still new, lots libraries are still not compatiable.
2. Efficiently process audio siginals and preserve accuracy
3. The Digital Siginal Processing requires lost of MATH and base knowledge
Housing
