Æthel Drive Hardware Design
Worked for 6 mins 41 sec
Completed the Æthel Drive schematic instantiation and wiring.
- Added and wired ESP32 DevKitC, L298N, MPU6050, SSD1306 OLED, ACS712-05B, LM2596 buck module, 12 V/E-stop connector, motor connector, I2C pull-ups, ADC dividers, decoupling/bulk capacitors, and L298N flyback diodes.
- Shared I2C bus is on GPIO21/GPIO22 with 4.7 kΩ pull-ups to 3.3 V.
- L298N channel A uses GPIO25 for PWM enable, GPIO26/GPIO27 for direction.
- ACS712 output and 0–12 V motor voltage are scaled before ESP32 ADC GPIO34/GPIO35.
- E-stop is wired as a hardware motor-rail cutoff path while keeping ESP32 logic powered.
- ERC/review now reports no open errors or warnings for the checked schematic categories.
Important voltage-level notes:
- I2C pull-ups are to 3.3 V, which is correct for ESP32.
- ACS712 is a 5 V part; its analog output is divided down before GPIO34.
- The OLED module is powered from 5 V but shares 3.3 V I2C pull-ups; this is acceptable only if the OLED module does not add onboard pull-ups to 5 V.
- The L298N accepts ESP32 3.3 V logic as HIGH in typical use, but verify the exact module/IC threshold if using a clone board.
I also created:
Schematic is ready for your review before moving to layout.
Proceed to layout
Fix voltage risks
Add test points
Review power sizing
Add debug header
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Project Specification: USB-C WiFi BLE T-RH Sensor
Project Overview
Status: Draft schematic in progress.
Design a consumer USB-C powered environmental sensor node that measures temperature and relative humidity and communicates over 2.4 GHz Wi-Fi 802.11 b/g/n and BLE 5.x.
Intended Use
Indoor consumer environmental monitoring powered from a USB-C 5 V source such as a wall adapter, hub, or computer port. The design is production-intent at schematic level but will need layout, RF keepout verification, and compliance testing before sale.
What the Device Should Do
- Accept 5 V from USB-C using default sink behavior.
- Protect against reverse input, over-voltage, under-voltage, and over-current conditions.
- Generate a regulated 3.3 V rail for the MCU and sensor.
- Measure temperature and relative humidity with a digital sensor.
- Communicate readings over Wi-Fi and BLE.
- Support USB programming/debug where the selected MCU supports native USB.
- Support low-power firmware modes even though the board is USB powered.
Main Features
- USB-C 5 V input, planned for 0.5 A to 3 A source capability.
- Wi-Fi + BLE MCU module with integrated RF matching and antenna.
- Digital I2C temperature/humidity sensor.
- Protected input path: CC resistors, ESD protection, eFuse/load switch class protection, UVLO/OVP/OCP, 3.3 V regulator.
- Boot/reset controls and status LED.
- Test points for 5 V, 3.3 V, GND, USB D+/D-, I2C, boot/reset.
System Architecture
Diagram
Hardware Subsystems
- Power input: USB-C receptacle configured as a sink with 5.1 kOhm CC pull-downs.
- Protection: use an integrated protected power-path/eFuse device where available for OVP/UVLO/OCP and reverse-current blocking, plus input TVS/ESD.
- Regulation: 5 V to 3.3 V regulator sized for ESP32-class radio current peaks.
- MCU/radio: ESP32-class module preferred to avoid custom RF matching and antenna design.
- Sensor: low-power digital T/RH sensor on I2C.
- Firmware/debug: native USB if using ESP32-S3/C3/C6; boot and reset controls included.
Interfaces and Connections
- External: USB-C receptacle for 5 V input and USB data/programming.
- Internal: I2C bus from MCU to T/RH sensor with pull-ups to 3.3 V.
- User/service: BOOT and RESET buttons, status LED, test points.
Power and Runtime Expectations
The device is USB-powered, not battery powered. Low-power firmware modes should still be supported to reduce heat and idle consumption. No runtime target applies unless a battery option is added later.
Power Tree and Power Budget
Initial target sizing before final datasheet confirmation:
- USB-C VBUS 5 V input, assume allowed source current may be 0.5 A, 1.5 A, or 3 A depending on source advertisement.
- Protected 5 V rail feeds 3.3 V regulator.
- 3.3 V rail powers MCU module, T/RH sensor, pull-ups, and status LED.
- Design for ESP32-class radio bursts of roughly 350-500 mA peak on 3.3 V plus small sensor/LED loads.
- Protection and regulator should be selected with margin for at least 600 mA peak system load, while firmware should not assume 3 A is available unless CC/current advertisement is monitored.
Manufacturing and Assembly Expectations
- SMD production assembly assumed.
- Use available library parts with real datasheets and manufacturable footprints.
- Keep RF antenna at board edge with copper keepout during layout.
- Add test points for bring-up.
Firmware-Relevant Hardware Requirements
- I2C pin assignments for sensor.
- Native USB programming/debug if supported by the selected MCU.
- BOOT and RESET buttons for recovery/programming.
- Status LED GPIO.
- Sleep-mode support in firmware.
Physical Design Expectations
- Small environmental node PCB for consumer indoor use.
- USB-C connector on board edge.
- MCU antenna at board edge with datasheet keepout, no copper under antenna.
- Sensor should be thermally separated from regulator/MCU heat sources and exposed to ambient air.
Important Design Decisions
- Prefer ESP32-S3/C3/C6 module over bare RF IC for integrated antenna/matching and easier certification path.
- Use USB-C default 5 V sink mode, not USB Power Delivery.
- Use I2C digital T/RH sensor for low power and simple firmware.
- Use protected power-path/eFuse style input protection rather than only a fuse/diode.
Assumptions
- Consumer indoor environment, non-safety-critical.
- USB-C provides only 5 V; no PD negotiation required.
- A module with integrated antenna is acceptable.
- SMD assembly is acceptable.
Change Notes
- Initial specification created from user requirements.
Project Overview
Intended Use
What the Device Should Do
Main Features
System Architecture
Hardware Subsystems
Interfaces and Connections
Power and Runtime Expectations
Power Tree and Power Budget
Manufacturing and Assembly Expectations
Firmware-Relevant Hardware Requirements
Physical Design Expectations
Important Design Decisions
Assumptions
Change Notes
