Designed the smart espresso scale schematic and renamed the project Smart Espresso Scale. The schematic now has 55 components / 44 nets, including USB-C power/ESD, BQ24295 Li-ion charger/power-path, 3.3 V regulation, ESP32-S3 BLE MCU, NAU7802 load-cell AFE, microSD logging, I2C OLED display, buttons, and status LEDs; verification found no open ERC/component/footprint errors in the checked categories.

Project files created:

Open items:

Select the final Li-ion cell capacity and set BQ24295 charge current accordingly; firmware currently notes a conservative ≤512 mA target.
Validate TLV1117 dropout/thermal margin during BLE + display + SD write bursts.
Verify the exact OLED/display module pinout and 3.3 V compatibility before production.
PCB layout still needs antenna keepout, charger/regulator thermal layout, and load-cell analog routing care.

Suggested next steps:

Proceed to PCB board size/constraints and component placement.
Choose the final battery capacity and enclosure/display mechanical constraints.
Run PCB layout with ESP32 antenna keepout and load-cell analog separation.
After placement, route and run full DRC/PI/SI checks.

Layout and fix risks

Proceed to layout

Fix open risks

Set design constraints

Run schematic review

Refine this doc

Ask about this doc

Board Bring-Up Plan — Smart Espresso Scale

Prerequisites

Equipment: current-limited USB supply, multimeter, oscilloscope, USB-C cable, known calibration weights, Li-ion cell simulator or protected 1S cell, PlatformIO firmware setup.
Firmware reference: see Firmware Starter.
Safety: use a protected Li-ion cell; do not connect an unknown bare cell without current limiting and polarity check.

1. Visual Inspection

Verify orientation and soldering of U2 BQ24295, U3 TLV1117LV33, U4 ESP32-S3 module, U5 NAU7802, U6 TPS22919, USB-C J1, microSD J5, battery connector J2, load-cell header J4, and polarized LEDs.
Inspect USB-C pins and microSD socket for bridges.

2. Power Rail Verification

Table

Rail	Source	Expected	Measure At	Current Limit	Pass Criteria
VBUS	USB-C `J1`	5.0 V	`J1` VBUS / `U2` VBUS	300 mA initial	4.75–5.25 V, no overheating
VBAT	Battery `J2` / charger `U2`	3.0–4.2 V	`J2`, `U2` BAT	100 mA first battery test	Correct polarity, no reverse current issue
VSYS	BQ24295 SYS	~3.5–4.4 V depending source/battery	`U2` SYS, `U3` IN	300 mA initial	Stable rail feeding regulator
3V3	TLV1117LV33 `U3`	3.3 V	`U3` OUT, `U4` 3V3	300 mA initial	3.20–3.40 V under idle firmware
3V3_SD	TPS22919 `U6` output	3.3 V when enabled	`U6` OUT / `J5` VDD	100 mA	Off before enable, 3.3 V after firmware enables SD power

Procedure:

With power off, measure resistance from VBUS, VBAT, VSYS, 3V3, and 3V3_SD to GND.
Apply USB-C at 5 V with 300 mA current limit and no battery installed.
Confirm VBUS, VSYS, and 3V3 in order.
Install protected cell or cell simulator; confirm VBAT polarity and charge behavior.
Run firmware and confirm 3V3_SD switches on only when SD is initialized.

3. Critical Signals

Table

Signal	Net	Expected State	Measure At	Notes
MCU enable	MCU_EN	High after RC delay	`U4` EN	Reset button should pull low if fitted
Boot strap	MCU_BOOT	Normal boot idle high/pulled state	`U4` BOOT GPIO	Hold BOOT during reset for loader mode
I2C	I2C_SDA/SCL	Idle high at 3.3 V	`U4`, `U5`, `DS1`	Scope for 400 kHz transactions
Load ADC ready	LOAD_DRDY	Pulses/low-ready	`U5` DRDY / `U4` IO8	Confirms NAU7802 conversions
USB data	USB_D+/USB_D-	Enumerates as USB serial	`J1`, `U4` IO19/20	Check ESD path continuity
Charger interrupt	CHG_INT	High idle, low on charger event	`U2` / `U4` IO7	Verify with battery attach/remove

4. Connector and Interface Tests

Table

Connector	Type	Test
`J1` USB-C	Power / native USB	Verify CC pull-down detection, 5 V VBUS, USB serial enumeration
`J2` B2B-PH-K-S	1S Li-ion	Verify polarity and charge current before real cell use
`J3` 2x3 header	UART/program/debug	Verify TX/RX/GND continuity and 3.3 V logic level
`J4` BHR-12-VUA	Load cell header	Verify excitation/signal wiring before attaching load cell
`J5` microSD socket	SPI storage	Insert card, confirm `shots.csv` creation
`DS1` OLED	I2C display	Confirm address 0x3C and visible weight readout

5. Programming and Debug

Connect USB-C and build/flash via PlatformIO.
If needed, hold BOOT, pulse reset, then upload.
Open 115200 baud monitor and confirm NAU7802:OK and SD status messages.
Confirm BLE advertisement name Smart Espresso Scale from a phone.

6. Functional Validation

Table

Test	Input	Expected Output	Pass Criteria
I2C scan	Firmware boot	Finds 0x2A, 0x3C, optionally 0x6B	All populated I2C devices respond
Load-cell raw data	Light pressure on load cell	Raw counts change monotonically	Stable zero, no large noise bursts
Tare button	Press `SW1`	Display returns near 0 g	Tare event works repeatedly
Start/stop	Press `SW2`	Logging toggles	CSV logging starts/stops
microSD logging	Insert FAT card	`/shots.csv` grows	Timestamp, grams, raw rows present
BLE notify	Phone connected	Weight characteristic updates	Updates about every 100 ms
Charger	Attach battery + USB	Status LED / I2C status changes	Charge current within selected cell limit

Open Bring-Up Items

Select final battery capacity and set BQ24295 charge current accordingly.
Verify OLED module pin order and 3.3 V compatibility before production.
Confirm TLV1117 thermal/dropout margin with worst-case battery and active microSD/BLE current.

Prerequisites
1. Visual Inspection
2. Power Rail Verification
3. Critical Signals
4. Connector and Interface Tests
5. Programming and Debug
6. Functional Validation
Open Bring-Up Items

Reviews

Documents

Project Specification — Smart Espresso Scale
Block Diagram — Smart Espresso Scale
Reference Recreation Ledger — Smart Espresso Scale
Power Budget — Smart Espresso Scale
Firmware Starter — ESP32-S3 Smart Espresso Scale
Board Bring-Up Plan — Smart Espresso Scale
Technical Construction File — Smart Espresso Scale
Safety Analysis — Smart Espresso Scale
Preliminary FMEA — Smart Espresso Scale

Assets

No assets added.

Project Name

Smart Espresso Scale

Description

BLE smart espresso scale with USB-C power, single-cell Li-ion battery charging, load-cell measurement, local data logging, and an integrated segment/display interface.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor	Qty 1
Arrow	$3.59–$4.32
Digi-Key	$1.90
HQonline	$1.48–$1.72
LCSC	$13.57–$14.21
Mouser	$15.81
TME	$7.01
Verical	$1.51–$2.05

Controls

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ryanf / Smart Espresso Scale

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