• Status: Draft schematic reconstruction in progress.
• Device: Credit-card-sized robot body carrier/adapter PCB connecting an RDKx5 main brain to an ESP32-S3 that manages serial-bus servos.
• Target board size: 85.60 mm × 53.98 mm, rectangular, 2-layer PCB.

• Prototype robot body electronics board for a biped robot.
• Routes control/data between the RDKx5, ESP32-S3, USB-C tuning/programming interface, I2C sensors, and serial-bus servos.
• Distributes raw battery power directly to servo bus connectors, similar to the Waveshare Serial Bus Servo Adapter A behavior.

• Accept battery input on a 2-pin connector.
• Feed the servo power rail directly from battery input.
• Generate 5 V using an LM2596S-5.0 buck regulator for the ESP32 VIN and RDKx5 5 V header pin.
• Provide USB-C tuning/programming through a CP2102C USB-UART bridge.
• Connect RDKx5 UART to the ESP32.
• Provide two servo bus connectors with power, ground, and data.
• Provide I2C/MPU6050 connectors.
• Provide a 3-pin battery-monitor connector and ADC-safe divided battery sense to the ESP32.
• Include shutdown switch, boot/reset controls, status LEDs, decoupling, and protection.

• ESP32-S3-WROOM-1 module.
• CP2102C USB-UART bridge.
• USB-C device/sink connector with independent 5.1 kΩ CC pull-downs.
• LM2596S-5.0 5 V buck regulator with external inductor, catch diode, and input/output capacitors.
• 3 A polyfuse in the battery/servo input path.
• SMBJ5.0A TVS requested on the 12 V rail; note this clamp voltage appears inconsistent with a nominal 12 V battery rail and should be reviewed.
• Two 3-pin servo bus connectors: 12V, GND, DATA.
• 4-pin RDK header: 5V, TX, RX, GND.
• 4-pin I2C header: 3.3V, GND, SDA, SCL.
• 4-pin MPU6050 header: 3.3V, GND, SDA, SCL.
• 3-pin battery monitor connector: VBAT, GND, ADC_SENSE.

Diagram

• Power input and distribution: Battery input, shutdown switch, protection, raw servo rail, and 5 V buck conversion.
• ESP32 control: ESP32-S3-WROOM-1 handles servo data, RDK UART, USB tuning bridge, I2C, ADC battery sense, boot/reset, and status LEDs.
• USB-C tuning/programming: USB-C sink/device connector with CC pull-downs, ESD/protection as needed, CP2102C UART bridge.
• Servo interface: Two D/V/G-style serial servo buses, raw battery power to V pin, data line level shifted to/from ESP32.
• RDKx5 interface: 5 V, TX, RX, GND header.
• Sensors: Shared I2C bus for generic I2C and MPU6050 connection.
• Battery monitor: Raw VBAT connector pin plus divided ADC_SENSE through 10 kΩ / 1 kΩ divider.

• Battery voltage is assumed nominally around 12 V unless corrected by the user.
• Servo current can be high and pulsed; servo rail must use wide traces/copper pours and connector/fuse ratings sized for real servo load.
• 5 V rail powers logic/RDK header, not the servo motor current.
• Runtime depends mostly on servo current draw and battery capacity; not yet specified.

• Compact SMD-oriented 2-layer prototype PCB.
• Wide copper for raw battery/servo current.
• Solid ground plane/fill on both layers where possible.
• ESP32 antenna at board edge with no copper keepout.
• Design should be DRC/ERC reviewed before Gerber export.

• Board outline: 85.60 mm × 53.98 mm rectangle.
• ESP32 antenna placed at an edge, facing outward, with copper keepout.
• Power input and servo connectors should be close to high-current copper paths.
• USB-C should be edge accessible.
• Shutdown switch should be accessible from the board edge.

• Servo V rail follows Waveshare adapter behavior: raw battery input is distributed to servos; it is not a regulated 5 V output.
• Use two separate servo data buses on GPIO25 and GPIO26.
• Use level shifting on servo data lines rather than direct 3.3 V connection.
• Use USB-C only as device/tuning/programming interface unless later upgraded for power delivery.
• 2-layer board selected by user request; dense/high-current routing may benefit from 4 layers if layout becomes difficult.

• Battery is assumed nominal 12 V; exact chemistry and max/min voltage are not yet specified.
• Servo peak current is not yet specified; 3 A fuse may be too small for multiple bus servos depending on stall current.
• SMBJ5.0A on a 12 V rail is likely incorrect because it clamps near 5 V and would conduct on a 12 V battery. A 12 V-compatible TVS should be selected unless the rail is actually 5 V.
• ESP32-S3 GPIO34 availability depends on exact module variant; GPIO35–42 are commonly reserved for flash/PSRAM on some ESP32-S3 modules, while GPIO34 may be available but must be verified against the selected module.
• GPIO43/44 are often UART0/log pins on ESP32-S3 and can be used for USB-UART, but boot/debug behavior should be checked.

• Board size changed from 61 mm × 71 mm to credit-card size.
• Battery monitor connector added.
• Pasted requirements now specify ESP32-S3-WROOM-1, CP2102C, LM2596S-5.0, two servo buses, RDK UART, USB-C tuning, I2C/MPU6050 headers, and ADC divider.