Multi-Functional Controller (MFC)

A custom, high-performance handheld remote controller engineered from scratch for dual-role applications: long-range, low-latency RC vehicle control and USB/Bluetooth HID gaming.

Built around the ESP32-S3 (Xtensa® 32-bit LX7 dual-core @ 240 MHz), this project bridges hardware and software engineering—combining magnetic Hall-effect sensing, RF telemetry, hardware pulse-counted rotary inputs, hardware PWM audio synthesis, and an SPI graphics pipeline into a unified, battery-powered embedded platform.

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Prototype Showcase

Figure 1: Top assembly layout — Dual Hall-effect joysticks, rotary encoder, tactile buttons, 1.3" SPI OLED display, NeoPixel telemetry bar, and audio transducers.

Figure 2: Ergonomic profile — 2.4 GHz high-gain dipole antenna connected to the NRF24L01+ RF transceiver, rotary dial, and dual USB-C ports.

Figure 3: Underbody point-to-point bus routing — 6×9 cm perfboard with dedicated decoupled power rails (100 µF smoothing capacitor) and direct GPIO signal lines.

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Key Hardware & Architectural Features

• Microcontroller Core: Espressif ESP32-S3-N16R8 (16 MB Quad SPI Flash, 8 MB Octal PSRAM) running FreeRTOS preemptive multitasking.
• Dual Wireless Pipelines:
  • 2.4 GHz RF (NRF24L01+): Dedicated SPI radio module with external SMA antenna for low-latency, deterministic RC telemetry.
  • Bluetooth 5.0 LE & Wi-Fi: Native wireless stacks for PC/gamepad HID modes and wireless telemetry streaming.
• Precision Analog & Digital Controls:
  • Dual Hall-Effect Joysticks: Contactless magnetic sensing for zero stick drift and extended durability.
  • Hardware Pulse-Counted Rotary Encoder: Quadrature decoding handled in hardware via the ESP32-S3 pulse_cnt peripheral to guarantee zero missed ticks during high-load processing loops.
  • Dedicated Navigation Buttons: Tactile push-buttons configured with internal pull-ups for UI interaction and control toggling.
• Multi-Sensor Audio & Visual Telemetry:
  • 1.3" SPI OLED Display (SH1106 / SSD1306): Driven via hardware DMA SPI (SPI2_HOST) with custom frame buffering for menus, telemetry, and live status readouts.
  • Polyphonic Melodic Synthesis: Passive buzzer modulated via hardware LEDC PWM timer (LEDC_TIMER_0, 13-bit duty resolution).
  • Percussive Acoustic Alerts: Dual active buzzers for instant tactile/auditory feedback and warning signals.
  • Visual Beat & Metric Indicators: Dedicated Kick (GPIO 21) and Hi-Hat (GPIO 22) LEDs alongside an 8-LED WS2812B NeoPixel RGB strip driven via RMT.
• Power Subsystem:
  • Dual parallel 18650 Li-ion cells delivering 4800 mAh combined capacity.
  • Dual USB-C ports: one dedicated for high-efficiency battery charging and one for USB-UART flashing, debugging, and wired HID gamepad control.
  • 100 µF low-ESR electrolytic capacitor buffering transient current spikes from RF transmission bursts and buzzer pulses.

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GPIO Pinout & Peripheral Mapping

The firmware (firmware/main/mmcontroller.c) allocates hardware peripherals across the ESP32-S3 as follows:

Peripheral / Signal	GPIO	Mode / Hardware Interface	Description
Rotary Encoder CLK	GPIO 32	ESP-IDF pulse_cnt Unit	Quadrature channel A (hardware edge counter)
Rotary Encoder DT	GPIO 33	ESP-IDF pulse_cnt Unit	Quadrature channel B (direction sensing)
Rotary Push Switch	GPIO 16	Digital Input (PULLUP)	Rotary push-button (mode / parameter select)
Button: Pause / Play	GPIO 13	Digital Input (PULLUP)	Navigation / transport control
Button: Next / Forward	GPIO 14	Digital Input (PULLUP)	Navigation / channel advance
Passive Buzzer	GPIO 25	LEDC PWM (LEDC_CHANNEL_0)	Hardware PWM audio synthesis (frequency & melody)
Active Buzzer 1	GPIO 26	Digital Output	Percussive acoustic click / telemetry alert 1
Active Buzzer 2	GPIO 27	Digital Output	Percussive acoustic click / telemetry alert 2
LED: Kick Trigger	GPIO 21	Digital Output	Visual beat / primary telemetry indicator
LED: Hat Trigger	GPIO 22	Digital Output	Visual beat / secondary telemetry indicator
OLED Data/Command (DC)	GPIO 2	Digital Output	1.3" OLED command vs data selection
OLED Reset (RES)	GPIO 4	Digital Output	Hardware display reset line
OLED Chip Select (CS)	GPIO 5	SPI Device Select (SPI2)	Display SPI bus enable
OLED Clock (CLK)	GPIO 18	SPI Master Clock (SPI2)	Hardware SPI clock line (DMA enabled)
OLED MOSI	GPIO 23	SPI Master Output (SPI2)	Hardware SPI data out line (DMA enabled)
NeoPixel RGB Bar	Config	RMT Peripheral	WS2812B 8-pixel addressable RGB telemetry strip

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Repository Structure

multi-functional-controller/
├── firmware/                        # ESP-IDF C99/C++ Firmware Project
│   ├── CMakeLists.txt               # Top-level CMake project configuration
│   ├── sdkconfig                    # ESP32-S3 configuration (PSRAM, Flash, FreeRTOS)
│   └── main/
│       ├── CMakeLists.txt           # Component registration
│       ├── idf_component.yml        # Espressif component dependencies (led_strip)
│       └── mmcontroller.c           # Core firmware: FreeRTOS tasks, pulse counter, SPI OLED, LEDC PWM
├── hardware/                        # KiCad 10 Electronic Design Automation (EDA)
│   ├── mfc-1.kicad_pro              # KiCad project file
│   ├── mfc-1.kicad_sch              # Complete schematic design & component symbols
│   └── mfc-1.kicad_pcb              # Board layout & routing rules
├── images/                          # High-resolution prototype photography
│   ├── TOP_VIEW.png                 # Front control surface overview
│   ├── SIDE_VIEW_WITH_ANTENNA.png   # RF antenna and profile perspective
│   └── BOTTOM_VIEW.png              # Perfboard underside bus wiring
├── .gitignore                       # Clean repository filter (builds, caches, local configs)
└── README.md                        # Master engineering documentation

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Getting Started: Building the Firmware

Prerequisites

• ESP-IDF v5.1+ installed and exported into your environment:

  . $HOME/esp/esp-idf/export.sh
  

Build & Flash

1. Navigate to the firmware directory:

   cd firmware
   

2. Set target to ESP32-S3:

   idf.py set-target esp32s3
   

3. Compile the firmware:

   idf.py build
   

4. Flash to the controller and open serial monitoring:

   idf.py -p /dev/ttyUSB0 flash monitor
   

   (Replace /dev/ttyUSB0 with your serial device node, e.g. /dev/ttyACM0).

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Hardware CAD & Schematic Editing

The electronic schematic is developed in KiCad 10:

1. Open the project:

   kicad hardware/mfc-1.kicad_pro
   

2. Inspect or modify the schematic in eeschema (hardware/mfc-1.kicad_sch).
3. To generate vector schematics for documentation or web publication:
   • Select File \rightarrow Plot \rightarrow SVG or PDF.

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Roadmap & Milestones

• Initial hardware breadboard and perfboard prototype (6×9 cm assembly).
• Dual-core ESP-IDF firmware setup with FreeRTOS task scheduling.
• Hardware pulse-counter integration for quadrature rotary encoder (driver/pulse_cnt.h).
• Hardware LEDC PWM audio synthesis & percussive buzzer drivers.
• High-speed SPI OLED graphics driver with DMA channel support.
• Addressable WS2812B NeoPixel telemetry integration.
• Custom multi-layer printed circuit board (PCB) design in KiCad.
• 3D-printable ergonomic handheld enclosure (PETG / Resin).
• Low-latency NRF24L01+ bidirectional packet protocol with ACK-payload telemetry.
• Standard USB Gamepad HID descriptor integration for plug-and-play PC gaming.

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Author & Project Notebook

• Author: Ertunç Özbay
• Personal Workshop & Portfolio: ertuncozbay.dev
• Project Detail Page: ertuncozbay.dev/projects/multi-functional-controller.html
• License: MIT License