ESP32 Flex Sensor Board Design
Thought for 4 sec
Work done
- Removed duplicate legacy schematic blocks and kept a single production path built around IC2, U5, J9, U6, U3, and U7
- Removed alternate/duplicate parts U1, U2, J1, IC1, J2, U4, U8, J7, J8, SW1, SW2, J4, J5, and J6
- Normalized USB net names to USB_DP and USB_DN, retained the 3-pin haptic connector scheme on J11 and J12, and added explicit no-connect markers for intentionally unused pins on IC2, U5, U7, U3, and J9
- Verified key power and interface rails: VBUS -> U5 -> VSYS -> U3 -> 3V3, battery rail VBAT to J10, USB native data from J9 through U6 to IC2, and boot/reset pull networks on SW3, SW4, R17, and R8
- Set the layout to 160 mm x 100 mm, 4-layer, with inner layer 2 as ground plane and inner layer 3 as a power-oriented plane, plus baseline board rules of 0.15 mm minimum trace width, 0.15 mm minimum keep-out, and 0.2 mm board inset margin
- Updated and saved project notes in Design Notes
Success criteria review
- ✅ The schematic was substantially cleaned up and duplicate major circuits were removed
- ✅ Power, USB, and ESP32 boot/reset circuitry were reviewed and consolidated into a single retained implementation
- ✅ Production MPN metadata was improved for key ICs including U3 and U7, and all current parts have footprints assigned
- ✅ The PCB layout size, stackup, and core board rules are now defined
- ❌ The layout is not yet fully routed: DRC still reports 82 airwire errors
- ❌ ERC still reports unresolved floating capacitor pins on C1, C7, C8, and C16
- ❌ I could not complete placement optimization or trace routing because the available toolset in this run does not include a placement or routing mutation tool, so I cannot finish the remaining PCB connectivity from here
Next steps
The design is materially cleaner and constrained, but it is not yet production-ready because routing and a few remaining schematic cleanup items are still open. If placement and auto-routing tools are made available in a follow-up run, I can finish the remaining airwires, resolve the last floating caps, and close the final ERC/DRC gap.
Clean up duplicates
Review critical circuits
Fix ERC/DRC issues
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Project Specification
Overview
A beginner-friendly, battery-powered ESP32 board with three flex sensor inputs, one I2C gyro, and two haptic output interfaces. The design uses a single USB-C connector for both charging and native USB programming, a single-cell LiPo battery charger with power-path management, and a shared 3.3V rail for the ESP32, sensor, and control logic.
Architecture
Diagram
Functional Blocks
- Power: USB-C sink input, LiPo charger with load sharing, battery connector, 3.3V regulation, input and rail decoupling.
- Control: ESP32-S3 module with native USB, BOOT and RESET pushbuttons, required bootstrap and enable support.
- Sensors: Three flex sensor connectors routed to ADC-capable GPIOs using resistor-divider interfaces, plus one I2C gyro with shared SDA/SCL pull-ups.
- Haptics: Two beginner-friendly external haptic driver module interfaces powered from 3.3V and controlled by dedicated ESP32 GPIO outputs.
Planned Pin Map
- USB: GPIO19 = USB D-, GPIO20 = USB D+
- BOOT: GPIO0
- RESET: CHIP_PU / EN
- I2C: GPIO8 = SDA, GPIO9 = SCL
- Flex ADC inputs: GPIO1, GPIO2, GPIO3
- Haptic control outputs: GPIO4, GPIO5
Power Strategy
- USB-C is configured as a 5V sink using 5.1k pull-down resistors on CC1 and CC2.
- USB VBUS feeds a single-cell LiPo charger with power-path management so the board can operate while charging.
- The charger system output feeds a 3.3V LDO for a clean shared logic rail.
- The ESP32 and each IC receive local decoupling, with bulk capacitance on the USB input and 3.3V rail.
Beginner-Friendly Design Goals
- One USB-C connector for both charging and programming.
- Functional grouping by power, controller, sensors, and haptics.
- Header-style sensor and haptic interfaces for easy bring-up.
- Minimal special circuitry beyond required bootstrap, pull-ups, and protection.
Initial Component Choices
- ESP32-S3-MINI-1-N16 module
- MCP73871 charger with power-path management
- 3.3V LDO in compact SOT-23-5 class package
- USB-C USB 2.0 receptacle
- 6-axis I2C IMU / gyro
- JST-PH 2-pin battery connector
Overview
Architecture
Functional Blocks
Planned Pin Map
Power Strategy
Beginner-Friendly Design Goals
Initial Component Choices
