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Multi-Functional Controller (MFC)

ESP-IDF Target MCU KiCad Language RTOS Status

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-N16R8 (Xtensa® 32-bit LX7 dual-core @ 240 MHz), this project bridges hardware and software engineering—combining analog/Hall-effect sensing on ADC1, 2.4 GHz nRF24L01+ RF telemetry, hardware pulse-counted (pulse_cnt) rotary inputs, and a shared high-speed SPI2_HOST (FSPI) bus driving both the 1.3" SH1106 OLED display and radio transceiver without bus collisions.

Prototype Showcase

Multi-Functional Controller Top View
Figure 1: Top assembly layout — ESP32-S3-N16R8 module, analog joystick, quadrature rotary encoder, 1.3" SH1106 SPI OLED display, and nRF24L01+ RF transceiver.

Multi-Functional Controller Profile & RF Antenna
Figure 2: Ergonomic profile — 2.4 GHz external dipole antenna connected to the nRF24L01+ transceiver, rotary dial, and dual USB-C ports.

Multi-Functional Controller Perfboard Soldering
Figure 3: Underbody point-to-point bus routing — 6×9 cm perfboard with dedicated decoupled power rails (100 µF smoothing capacitor across nRF24L01+ VCC/GND) and direct FSPI signal lines.

Key Hardware & Firmware Architecture

  • Microcontroller Core: Espressif ESP32-S3-N16R8 (16 MB Quad SPI Flash, 8 MB Octal PSRAM) running FreeRTOS.
  • Collision-Free Shared FSPI (SPI2_HOST) Bus:
    • Shares MOSI (GPIO 11), MISO (GPIO 13), and SCK (GPIO 12) between the 1.3" SH1106 OLED (10 MHz clock) and the nRF24L01+ 2.4 GHz Transceiver (1 MHz clock) via independent hardware Chip Select lines (GPIO 10 and GPIO 14).
  • Bare-Metal 5×8 OLED Graphics Engine & Multi-Screen UI State Machine:
    • Direct register-level driver for the 1.3" SH1106 controller (handling the 132×64 internal RAM 2-pixel column offset) with a complete 5×8 bitmap font table (A–Z, 0–9, <, >, [, ], (, ), /, -, :, .).
    • 4 Interactive Screens:
      1. DRIVE VEHICLE: Real-time One-Shot ADC1 joystick acquisition (VRx / VRy) and live 2.4 GHz packet broadcasting (rc_packet_t).
      2. RADIO CONFIG: Verifies physical nRF24L01+ SPI link (SETUP_AW register 0x03) and tunes RF_CH (register 0x05) live across channels 0–125 (2.400–2.525 GHz) using the rotary dial.
      3. CALIBRATE: Live raw ADC1 readout (0–4095) with one-click neutral center-point capture.
      4. SYSTEM INFO: Displays target silicon (ESP32-S3) and real-time free RTOS heap memory (esp_get_free_heap_size()).
  • Hardware Quadrature Rotary Decoder (pulse_cnt):
    • Uses the ESP32-S3 hardware Pulse Counter peripheral on GPIO 15 (CLK) and GPIO 16 (DT) with a 1000 ns hardware glitch filter and full 4× quadrature edge/level state decoding, paired with a 300 ms debounced push-switch (GPIO 17).
  • Wi-Fi-Safe Analog Joystick Acquisition (ADC1):
    • Routes VRx (GPIO 4, ADC1_CH3) and VRy (GPIO 5, ADC1_CH4) with 12 dB attenuation (0–3.3V full-scale) on ADC_UNIT_1 to avoid ADC2 Wi-Fi/RF arbitration conflicts.
  • Power Subsystem:
    • Dual parallel 18650 Li-ion cells delivering 4800 mAh combined capacity.
    • 100 µF low-ESR electrolytic bulk decoupling capacitor suppressing nRF24L01+ TX current spikes.

GPIO Pinout & Peripheral Mapping (ESP32-S3 Hardware Specification)

The physical controller uses a shared high-speed SPI2_HOST (FSPI) bus for both the 1.3" SH1106 OLED and the nRF24L01+ RF transceiver, alongside dedicated ADC1 channels and hardware pulse-counter inputs:

Peripheral / Signal GPIO Hardware Interface Description
SPI Bus: MOSI GPIO 11 SPI Master Output (SPI2_HOST) Shared data line for nRF24L01+ and OLED (SDA / D1)
SPI Bus: MISO GPIO 13 SPI Master Input (SPI2_HOST) Data line from nRF24L01+ radio module
SPI Bus: SCK (Clock) GPIO 12 SPI Master Clock (SPI2_HOST) Shared clock line for nRF24L01+ and OLED (CLK / D0)
nRF24L01+ Chip Select (CS) GPIO 14 SPI Device Select Dedicated radio bus enable
nRF24L01+ Chip Enable (CE) GPIO 21 Digital Output Radio TX/RX power state activation line
OLED Chip Select (CS) GPIO 10 SPI Device Select Display SPI bus enable
OLED Data/Command (DC) GPIO 9 Digital Output 1.3" OLED command vs. data selection
OLED Reset (RES) GPIO 8 Digital Output Hardware display reset line
Joystick VRx (X-Axis) GPIO 4 ADC1 Channel 3 (12 dB Atten) Analog X-axis potentiometer input (0–3.3V safe)
Joystick VRy (Y-Axis) GPIO 5 ADC1 Channel 4 (12 dB Atten) Analog Y-axis potentiometer input (0–3.3V safe)
Rotary Encoder CLK GPIO 15 ESP-IDF pulse_cnt Unit Quadrature channel A (hardware edge counter)
Rotary Encoder DT GPIO 16 ESP-IDF pulse_cnt Unit Quadrature channel B (direction sensing)
Rotary Encoder Switch (SW) GPIO 17 Digital Input (PULLUP) Push-button (menu enter/select mode)

Silicon Multiplexing Notes (ESP32-S3-N16R8 vs. Classic ESP32)

  1. Octal PSRAM & Flash Reservation (GPIO 26 – GPIO 37): On the ESP32-S3-N16R8 (8 MB Octal PSRAM), GPIO 26 through GPIO 37 are wired internally to the Octal SPI Flash/PSRAM bus. Accessing GPIO 26, 27, 32, 33 triggers an immediate Guru Meditation Error / Cache Disabled Panic on boot.
  2. Unbonded Silicon Pins (GPIO 22 – GPIO 25): GPIO 22, 23, 24, 25 do not exist on the ESP32-S3 pin multiplexing matrix.
  3. FSPI (SPI2_HOST) Default Matrix: Uses native ESP32-S3 FSPI pins (GPIO 10, 11, 12, 13) for zero-penalty IOMUX/GPIO matrix routing rather than legacy 2016 ESP32 VSPI defaults (GPIO 5, 18, 23).

Repository Structure

multi-functional-controller/
├── firmware/                        # ESP-IDF C99 Firmware Project (ESP32-S3)
│   ├── CMakeLists.txt               # Top-level CMake project configuration
│   ├── sdkconfig                    # ESP32-S3 target configuration
│   └── main/
│       ├── CMakeLists.txt           # Component registration
│       └── mmcontroller.c           # Master firmware: Shared SPI2, SH1106 5x8 UI, nRF24L01+, PCNT, ADC1
├── 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)
├── LICENSE                          # MIT License
└── README.md                        # Master engineering documentation

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/ttyACM0 flash monitor

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.

Roadmap & Milestones

  • Initial hardware breadboard and perfboard prototype (6×9 cm assembly).
  • Shared SPI2_HOST bus driving both 1.3" SH1106 OLED and nRF24L01+ without bus collisions.
  • Full 5×8 bare-metal font renderer (A–Z, 0–9, and UI punctuation/symbols).
  • Hardware pulse-counter (pulse_cnt) quadrature decoder with 1000 ns glitch filter & 300 ms debounced state machine.
  • Live nRF24L01+ SPI register verification (0x03) and channel tuning (0–125) with ADC1 joystick packet transmission.
  • Custom multi-layer printed circuit board (PCB) design in KiCad.
  • 3D-printable ergonomic handheld enclosure (PETG / Resin).
  • Bidirectional ACK-payload telemetry from target RC vehicle.
  • Native USB Gamepad HID descriptor integration on ESP32-S3 USB-OTG port.

Author & Project Notebook