The document summarizes a project to build a guitar effect pedal using a microcontroller. It outlines the circuit design, which focuses on digital processing for effects like distortion, overdrive, equalizer, compressor, delay, and reverb. Open source software and libraries were used, including STM32 Cube, FATFS, uGFX, and ARM DSP libraries, to help implement the digital signal processing and user interface. Python and MATLAB were also used to simulate effects algorithms before implementation. Challenges included ensuring compatibility with new HAL firmware and efficiently processing audio signals while maintaining accuracy.

1. uRock
Music On MCU
by Sonicyang Anarchih KK Hirokiht

2. Outline
● Project Target
● Circuit Design
● How community helped us
● How Effect works and Implementation
● Wav Playing and Recoder
● UI
● Challanges & Obstacles
● Housing

3. Project Target - Inspiration
At 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.

4. What is Effect Pedal

5. Circuit Design
On our Design we want most of the work done digitally.
The analog Circuit mainly contains some amplifiers and
voltage regulators only.

6. Amplifiers and Level Shifters

7. Voltages Regulators
The 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.

8. 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

9. STM32 Cube
New HAL Firmware means fewer bugs.
Handy STM32 Cube MX software, Generate
Hardware related Initializing code.
Comes with multiple Middlewares.
● FreeRTOS
● FATFS

10. uGFX
Ported to base on
Cube Firmware and FreeRTOS
Very Flexible and portable, eased our pain on
UI designing.

11. 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.

12. Effect
● Distortion
● Overdrive
● Equalizer
● Compressor
● Delay
● Reverb

13. 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.

14. Aid of Python and MATLAB
To simulate the Effects and visualize before
hands. we use python and MATLAB to test the
algorithms.

15. Effect - Overdrive & Distortion

16. Effect - Compressor

17. Effect - Delay
The internal SRAM is not deep enough, thus
we store the delay data on external SDRAM.

18. Effect - Equalizer
Use IIR Filter to filter the audio.
Coefficient designing base on MATLAB’s aid.

19. 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

20. UI

21. 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

22. Housing