Smart Espresso Scale

Created 3 project docs

Firmware Starter — ESP32-S3 Smart Espresso Scale

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MCU: ESP32-S3-WROOM-1-N8R8 Framework: Arduino via PlatformIO

Board Bring-Up Plan — Smart Espresso Scale

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Multimeter, USB current meter, oscilloscope, 500 mA current-limited USB supply if available. Firmware from the Firmware Starter project file...

Regulatory FCC/CE Notes — Smart Espresso Scale

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Draft design-stage notes for a wireless USB-powered consumer device. | Module | Technology | Notes |

flux

Implemented 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:
  1. Replace L1 with a real inductor MPN.
  2. Start PCB layout with ESP32 antenna at the board edge.
  3. Add test points for 3V3, 3V3_AFE, NAU_DRDY, I2C, SPI, and load-cell signals.
  4. Route and run DRC/SI checks.
Finish layout prep
Replace L1
Verify OLED power
Add test points
Start PCB layout
Run schematic review
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Schematic

Layout

3D View

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



  
    
  
  
    
  























USB-C node_5V input
VBUS fuse + ESD protection
3.3V regulator
ESP32-S3-WROOM module
HX711 load-cell ADC
I2C OLED display
microSD card
4-wire load cell connector
Phone via BLE
ESP32-S3 native USB programming
Hardware Subsystems

Table

SubsystemDesign Direction
PowerUSB-C 5 V sink, protected VBUS, single 3.3 V rail sized for ESP32 peaks + display + SD + HX711.
Compute/connectivityESP32-S3 module, BLE primary phone link, Wi-Fi reserved for OTA/cloud.
Scale front-endHX711 ADC with 4-wire load-cell connector; analog input filtering and clean 3.3 V supply.
Display/UII2C OLED display, tare/start buttons, status LED.
Local storagemicroSD socket on SPI, 3.3 V signaling.
Debug/programmingUSB D+/D- to ESP32-S3 native USB, BOOT and RESET buttons.
ProtectionUSB 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

RailLoadsEstimated Current
USB VBUS 5 V3.3 V regulator input300 mA typical budget / 500 mA design target
3.3 VESP32-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