- **Primary Goal:** Engineer a high-performance, bare-metal handheld remote controller (**MFC**) from scratch using an **ESP32-S3-N16R8**, paired with a custom **4WD RC Vehicle** controlled by an **ARM Cortex-M3 (`GD32F103C8T6`)**.
- **Secondary Objectives:** Extend the controller's capabilities to include a **cloud-connected AI voice assistant** (`MAX4466`), **local FAT32 SD card telemetry logging**, and **PC Gamepad (`USB HID / Bluetooth`)** support.
> The photographs and schematic below represent the **very early initial stage** of the physical hardware build. At this stage, only the core carrier foundation is soldered onto the 6×9 cm perfboard: the **ESP32-S3-N16R8 microcontroller**, **nRF24L01+ 2.4 GHz radio module**, **100 µF electrolytic burst-smoothing capacitor**, **signal male pin headers**, and **power rail male headers**.
> The repository's firmware (`firmware/main/mmcontroller.c`) and schematic (`hardware/mfc-1.kicad_sch`) are intentionally kept matched to this verified **Rev 0.1 hardware baseline**. As the new modules (`1.8" ST7789 TFT`, `K-Silver PS5 Hall-Effect Joysticks`, `MicroSD`, `MAX4466`, `2N2222` buzzer stage, and enclosure) are physically integrated, both the hardware photos and firmware will be updated step-by-step.
- **Controller Prototype (Rev 0.1):** Prototyped on a **6×9 cm perfboard**. The `ESP32-S3-N16R8` communicates over a shared `SPI2_HOST` bus with a Nordic `nRF24L01+` 2.4 GHz transceiver and a temporary benchtop 1.3" SH1106 OLED display connected via the male breakout headers.
- **Current Baseline Firmware:** A deterministic FreeRTOS state machine (`firmware/main/mmcontroller.c`) handles hardware quadrature decoding (`PCNT`) for a `KY-040` rotary encoder menu UI, `300 ms` software button debouncing, and live 2.4 GHz RF channel configuration (`0–125`).
- **Display Hardware Pivot (`1.3" OLED` $\rightarrow$ `1.8" ST7789 TFT`):** Bench testing revealed that the 7-pin 1.3" OLED module lacks a physical Chip Select (`CS`) pin (hard-tied to GND internally), causing SPI bus collisions when sharing the bus. We are upgrading to a **1.8" ST7789 Color TFT LCD** (which exposes a dedicated hardware `CS` pin on `GPIO 10`) to share the SPI bus safely without bus contention.
- **Manufacturing & Enclosure Status:** Paused cutting the rigid ABS plastic project box (`DT-100`, `190 × 137 × 59 mm`) until next month when a variable 3-speed rotary tool (`Dremel/E108`) and `2.35 mm` diamond cutting wheels arrive to ensure clean, professional cutouts without melting the ABS plastic.
<imgsrc="images/TOP_VIEW.png"alt="Early Prototype Rev 0.1 Top View"width="700">
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<em><b>Figure 1 (Early Build — Rev 0.1):</b> Initial 6×9 cm perfboard carrier top view — ESP32-S3-N16R8 module, nRF24L01+ 2.4 GHz transceiver, 100 µF decoupling capacitor, peripheral male pin headers, and power rail male headers. (Will be updated as Phase 2 modules are installed).</em>
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<imgsrc="images/SIDE_VIEW_WITH_ANTENNA.png"alt="Early Prototype Rev 0.1 Side Profile & RF Antenna"width="700">
<em><b>Figure 2 (Early Build — Rev 0.1):</b> Side profile showing the external 2.4 GHz SMA dipole antenna connected to the nRF24L01+ transceiver and dual USB-C ports (Native USB-OTG & UART).</em>
<em><b>Figure 3 (Early Build — Rev 0.1):</b> Underbody point-to-point solder bridges, common ground/power rails, and shared SPI2 signal routing on the 6×9 cm perfboard.</em>
| **Voice AI** | **MAX4466 Electret Microphone Module** | Analog pre-amplifier with adjustable gain for cloud-connected AI voice assistant input. | **Next Upgrade** |
| **Data Logging** | **Arduino Micro SD Card Module** | SPI interface, formatted `FAT32` for local telemetry and configuration logging. | **Next Upgrade** |
| **Audio Output** | **1× Passive Buzzer + 2× Active Buzzers** | Passive buzzer for melodies + 2× active buzzers for percussive UI clicks, driven by **2N2222 NPN Transistors**. | **Next Upgrade** |
| **RF Telemetry** | **nRF24L01+ PA+LNA Module** | High-power 2.4 GHz transceiver with Power Amplifier, Low-Noise Amplifier, and external SMA antenna (~1 km range). |
| **IMU / Navigation**| **MPU9250 9-DOF Sensor** | 3-axis Gyroscope, 3-axis Accelerometer, and 3-axis Magnetometer (I2C) for tilt-compensated heading. |
| **Drivetrain** | **4× JGB37-520 12V 333 RPM Gear Motors** | High-torque 12V DC gear motors with built-in quadrature encoders for closed-loop PID velocity control. |
1.**Enclosure Machining RPM Rule:** Do **NOT** use standard fixed `16,000 RPM` rotary tools on the `DT-100` ABS plastic enclosure; high friction melts ABS instead of cutting it. Machining is paused until the variable 3-speed rotary tool with `2.35 mm` diamond cutting discs arrives.
2.**Hall-Effect Gimbal Polarity Protection:** Do **NOT** wire the K-Silver (KS) PS5 Hall-effect joystick `VCC` backward. Unlike passive carbon potentiometers, these are active 3.3V CMOS magnetic sensors and will burn out immediately under reverse polarity.
3.**5V Sensor Level Shifting on GD32:** Do **NOT** wire a 5V `HC-SR04` ultrasonic `ECHO` pin directly to the 3.3V `GD32F103C8T6` without a resistor voltage divider (or use the 3.3V `VL53L0X` I2C Time-of-Flight sensor instead).
4.**nRF24L01+ Burst Decoupling:** Always keep the `100 µF` electrolytic capacitor across the `nRF24L01+``VCC`/`GND` pins (alongside a `100 nF` ceramic cap for high-frequency noise) to prevent 3.3V rail brown-outs during PTX transmission bursts.
5.**2N2222 Base Resistor & Flyback Protection:** Always place a **`1 kΩ` series resistor** between the ESP32-S3 GPIO pin and the Base (`B`) of each `2N2222` NPN transistor (an unresisted BJT base clamps the GPIO to `0.7V` and draws excessive current). Place a **`1N4001` flyback diode** in reverse-parallel across inductive buzzer coils.
6.**Multi-Slave SPI Bus Initialization Rule:** When sharing `SPI2_HOST` across `nRF24L01+` (`GPIO 14`), `TFT Display` (`GPIO 10`), and `MicroSD` (`GPIO 18`), configure all three `CS` pins as outputs and drive them **HIGH (`1`)** prior to initializing the first SPI device so uninitialized slaves do not corrupt `MISO` (`GPIO 13`).
1.**1.8" ST7789 TFT Migration:** Rewrite the display initialization and frame buffer logic using ESP-IDF's `esp_lcd` component to replace the custom 5×8 monochrome OLED driver once the CS-equipped TFT module is wired. *(Note: Verify whether the 1.8" PCB uses the `ST7789` or `ST7735S` driver IC on arrival; both use identical SPI wiring and `esp_lcd` panel APIs).*
2.**MicroSD Card SPI & FATFS Setup:** Configure the Arduino MicroSD card module on the shared SPI bus and initialize the `FATFS` virtual filesystem (`VFS`) for reading/writing telemetry logs.
3.**NVS Hall-Effect Joystick Calibration:** Write the calibration routine for the K-Silver PS5 Hall-effect joysticks—measuring resting center, minimum, and maximum voltages and saving them persistently to ESP32-S3 Non-Volatile Storage (`NVS`) flash.
4.**GD32F103C8T6 Vehicle Receiver Firmware:** Structure the ARM Cortex-M3 C codebase to poll the `nRF24L01+ PA+LNA` module, read `MPU9250` 9-DOF I2C telemetry, and run closed-loop PID motor control on the 4×`JGB37-520` encoder motors.
