- **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.
- **Controller Prototype:** Currently 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 1.3" SH1106 OLED display, decoupled by a `100 µF` electrolytic capacitor across the radio rails.
- **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, `ADC1` joystick polling, 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, 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.
<em><b>Figure 2:</b> Side Profile — 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:</b> Underbody Bus Routing — Point-to-point solder bridges, common ground/power rails, and shared SPI2 signal routing on the 6×9 cm perfboard.</em>
| **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 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 to prevent 3.3V rail brown-outs during PTX transmission bursts.
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## 6. Immediate Next Steps & Engineering Roadmap
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.
2.**MicroSD Card SPI & FATFS Setup:** Configure the Arduino MicroSD card module on the 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.
