Smart Espresso Scale
Worked for 17 mins 12 sec
Created 3 project docs
Firmware Starter — ESP32-S3 Smart Espresso Scale
MCU: ESP32-S3-WROOM-1-N8R8 Framework: Arduino via PlatformIO
View docBoard Bring-Up Plan — Smart Espresso Scale
Multimeter, USB current meter, oscilloscope, 500 mA current-limited USB supply if available. Firmware from the Firmware Starter project file...
View docRegulatory FCC/CE Notes — Smart Espresso Scale
Draft design-stage notes for a wireless USB-powered consumer device. | Module | Technology | Notes |
View docImplemented the smart espresso scale schematic: USB-C power/data, 1.5 A 3.3 V buck rail, ESP32-S3 BLE/USB MCU, NAU7802 load-cell ADC, I2C OLED screen, microSD local logging, buttons, and status LED. I also created/updated the design files: Project Specification, Power Budget, Firmware Starter, Board Bring-Up Plan, and Regulatory FCC/CE Notes. ERC validation for the checked schematic categories is clean.
Open items:
- L1 is still a generic 3.3 µH inductor requirement; it should be replaced with a real shielded inductor MPN before manufacturing.
- Confirm the selected OLED module accepts 3.3 V on its VCC/“5V” pin.
- Layout is not done yet; antenna keepout, buck SW-node placement, and quiet load-cell routing are critical.
Suggested next steps:
- Replace L1 with a real inductor MPN.
- Start PCB layout with ESP32 antenna at the board edge.
- Add test points for 3V3, 3V3_AFE, NAU_DRDY, I2C, SPI, and load-cell signals.
- Route and run DRC/SI checks.
Finish layout prep
Replace L1
Verify OLED power
Add test points
Start PCB layout
Run schematic review
Refine this doc
Ask about this doc
Project Specification — Smart Espresso Scale
Project Overview
Status: Draft schematic design.
USB-C powered smart espresso scale with phone connectivity, live weight/timer display, local shot data logging, and firmware/debug access.
Intended Use
- Countertop espresso workflow: tare cup, start timer, stream weight to phone, log dose/yield/time locally.
- Prototype-to-small-production direction; SMD assembly assumed.
- Indoor, low-voltage consumer device near water/steam; USB-C supply only, no internal battery in this revision.
What the Device Should Do
- Measure espresso weight from a 4-wire load cell with gram/sub-gram resolution target.
- Show live weight, timer, and basic state on a local display.
- Connect to a phone over BLE; Wi-Fi available for future OTA/cloud features.
- Store shot logs locally when phone is disconnected.
- Power from USB-C 5 V sink input.
- Support firmware programming and debug.
Main Features
- ESP32-S3 module for BLE/Wi-Fi, native USB programming, and enough GPIO for display/storage.
- HX711 24-bit load-cell ADC for bridge measurement.
- I2C OLED display for readable timer/weight UI.
- microSD over SPI for local CSV/log storage.
- USB-C sink input with CC pull-downs, VBUS protection, and 3.3 V regulation.
- BOOT/RESET buttons plus status LED and user buttons.
System Architecture
Diagram
Hardware Subsystems
Table
| Subsystem | Design Direction |
|---|---|
| Power | USB-C 5 V sink, protected VBUS, single 3.3 V rail sized for ESP32 peaks + display + SD + HX711. |
| Compute/connectivity | ESP32-S3 module, BLE primary phone link, Wi-Fi reserved for OTA/cloud. |
| Scale front-end | HX711 ADC with 4-wire load-cell connector; analog input filtering and clean 3.3 V supply. |
| Display/UI | I2C OLED display, tare/start buttons, status LED. |
| Local storage | microSD socket on SPI, 3.3 V signaling. |
| Debug/programming | USB D+/D- to ESP32-S3 native USB, BOOT and RESET buttons. |
| Protection | USB CC pull-downs, VBUS fuse/TVS, USB data ESD preferred. |
Interfaces and Connections
- USB-C: 5 V input and native ESP32-S3 USB data/programming.
- BLE: phone connection for live data and control.
- I2C: OLED display.
- SPI: microSD card.
- GPIO: HX711 DOUT/SCK, BOOT/RESET, buttons, LED.
- External mechanical/electrical: load-cell connector.
Power and Runtime Expectations
- USB-C powered only; no battery/runtime target in this revision.
- Assumed USB source can provide at least 500 mA.
- Device peak current target: under 500 mA.
Power Tree and Power Budget
Table
| Rail | Loads | Estimated Current |
|---|---|---|
| USB VBUS 5 V | 3.3 V regulator input | 300 mA typical budget / 500 mA design target |
| 3.3 V | ESP32-S3, OLED, microSD, HX711, LED, pull-ups | ~250 mA typical active, ~420 mA peak |
Thermal note: 5 V to 3.3 V LDO at 250 mA dissipates about 0.43 W. Use a regulator/package with adequate thermal performance or switch to a buck regulator if sustained high Wi-Fi + display + SD current is expected.
Manufacturing and Assembly Expectations
- 2-layer prototype acceptable; 4-layer preferred for RF/USB/ground integrity.
- SMD assembly assumed; use common JLCPCB/LCSC-friendly components where possible.
- Add test points for VBUS, 3V3, GND, HX711 signals, I2C, SPI, BOOT/RESET.
Firmware-Relevant Hardware Requirements
- BLE GATT service for live weight/time and shot logs.
- microSD filesystem for CSV or binary log records.
- OLED UI: weight, timer, connection/storage state.
- Tare/start/stop buttons with debouncing.
- HX711 sampling and calibration routine.
- Native USB serial logging and firmware upload.
Physical Design Expectations
- Small board intended for integration under/inside a scale platform.
- ESP32 antenna must sit at board edge with copper keepout.
- USB-C connector must be accessible at enclosure edge.
- Load cell connector routed away from noisy digital/display/storage traces.
Important Design Decisions
- Choose ESP32-S3 module over bare RF chip to avoid custom RF matching and simplify certification path.
- Use HX711 for first revision due to strong scale ecosystem support and adequate resolution.
- Use OLED screen rather than segment-only display for richer UI unless user requests LED segments specifically.
- Use microSD for local data storage because shot logs can be removed/read without wireless.
Assumptions
- USB-C power only; no battery charging.
- Phone connection is BLE first; Wi-Fi reserved.
- 4-wire load cell, external to this PCB.
- Display is a small I2C OLED module/connector or onboard OLED footprint depending available library parts.
- Target capacity around 2 kg with sub-gram resolution after calibration.
Change Notes
- Initial architecture and requirements inferred from the user request.
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
