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

Preview

Resistance

5.1kΩ

R17

Resistance

10kΩ

R15

Resistance

10kΩ

Resistance

4.7kΩ

Resistance

100 Ω

Resistance

100 Ω

R14

Resistance

10kΩ

R10

Resistance

4.7kΩ

Resistance

4.7kΩ

R18

Resistance

10kΩ

Resistance

5.1kΩ

Resistance

330 Ω

R16

Resistance

10kΩ

Resistance

10kΩ

Resistance

10kΩ

Capacitance

4.7µF

Capacitance

10uF

Capacitance

1uF

Inductance

3.3uH

SW4

Capacitance

4.7µF

Capacitance

.1uF

C10

Capacitance

10uF

Capacitance

1uF

SW1

C11

Capacitance

10uF

C12

Capacitance

1uF

Capacitance

1uF

SW3

Capacitance

1uF

SW2

End of Life

Capacitance

22uF

DISP1

FB1

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