Smart Espresso Scale

Worked for 17 mins 12 sec

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:

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

Files

Schematic

Layout

3D View

Board Bring-Up Plan — Smart Espresso Scale

Prerequisites

Multimeter, USB current meter, oscilloscope, 500 mA current-limited USB supply if available.
Firmware from the Firmware Starter project file.
Do not connect a load cell until 3V3_AFE is verified.

1. Visual Inspection

Confirm U1 ESP32-S3 module orientation and antenna keepout.
Confirm J1 USB-C, J2 microSD, J3 load-cell connector, and all polarized/IC orientations.
Inspect buck regulator U3, L1, C2/C3 for shorts around the SW node.

2. Power Rail Verification

Table

Rail	Source	Expected	Measure At	Current Limit	Pass Criteria
VBUS_RAW	J1 USB-C	5 V	J1/F1 input	500 mA	4.75–5.25 V present.
VBUS_5V	F1 output	5 V	C1/C2 positive	500 mA	Within 100 mV of VBUS_RAW at idle.
3V3	U3 ST1S06 buck	3.3 V	C3/U1 3V3	500 mA	3.23–3.37 V.
3V3_AFE	FB1 filtered rail	3.3 V	C9/C10/J3 pin 1	100 mA	Within 50 mV of 3V3 at idle.
3V3_SD	U5 load switch	3.3 V when enabled	C11/J2 VDD	300 mA	Off at reset if firmware keeps SD_PWR_EN low; 3.3 V when enabled.

3. Critical Signals

Table

Signal	Expected State
ESP_EN	High after power-up; low while RESET pressed.
ESP_BOOT	High normally; low while BOOT pressed.
USB_D_P / USB_D_N	Enumerates as ESP32-S3 USB serial/JTAG when flashed.
I2C_SDA / I2C_SCL	Pull high to 3.3 V; 400 kHz traffic after firmware starts.
NAU_DRDY	Toggles/interrupts when NAU7802 conversions complete.
SD_PWR_EN	Firmware-controlled output on GPIO21.

4. Interface Tests

USB: verify enumeration and firmware upload over native USB.
I2C: run bus scan; expect OLED at 0x3C and NAU7802 at its configured address.
microSD: enable U5, mount card, create /shots.csv, and verify writes.
Load cell: connect E+/S+/S-/E- to J3 pins 1/2/3/4; verify raw counts change monotonically with applied mass.
BLE: phone should see EspressoScale advertising and receive weight/timer notifications.

5. Functional Validation

Table

Test	Pass Criteria
Tare button	Weight reads near 0 g after press.
Start/stop button	Timer toggles and OLED updates.
OLED	Shows weight, timer, BLE/SD status.
microSD logging	CSV rows append at runtime and survive power cycle.
Scale calibration	Known mass reads within target tolerance after calibration.
RF range	BLE remains connected with intended enclosure/top plate installed.

Open Bring-Up Risks

L1 is currently a generic 3.3 uH requirement; install a real shielded inductor with correct current rating.
Verify OLED module accepts 3.3 V on its VCC/5V pin.
Metal scale tray/enclosure may reduce ESP32 antenna range; test with real mechanics.

Prerequisites
1. Visual Inspection
2. Power Rail Verification
3. Critical Signals
4. Interface Tests
5. Functional Validation
Open Bring-Up Risks