WiFi Water Flow Meter Design
Route the USB and power traces with 4-layer stackup constraints.
Thought for 10 sec
I’ll route only the USB and power nets now, keeping the existing placement intact. I’ll confirm the 4-layer stackup, set appropriate width/clearance rules for USB 2.0 and power rails, clean any stale dangling traces, route, then run DRC on the routed nets.
Worked for 18 mins 59 sec
The routing pass hit the platform timeout after the stackup/rules were applied. I’m checking whether any routes were committed, then I’ll either validate them or report the routing blockage cleanly.
Worked for 59 sec
I set the board to a 4-layer stackup with inner GND and power planes, added wider minimum trace rules for USB/power nets, and confirmed there were no dangling traces before routing.
The routing job timed out and did not commit usable routes; review still shows 91 airwires. The blocker appears to be platform routing timeout/board routing complexity, not missing stackup or rules.
Route USB pair
Route power nets
Check routing blockers
Improve placement
Review stackup rules
Refine this doc
Ask about this doc
WiFi Water Flow Meter - Design Details
Scope Implemented
A USB-C powered, battery-backed ESP32-S3 water flow meter controller was created for a 3/4 inch PVC pipe ultrasonic RS485 sensor. The design now includes:
- USB-C 5 V input with CC pull-downs, resettable fuse, and VBUS ESD protection.
- Rechargeable 1-cell LiPo battery input using a JST-PH connector.
- BQ24074 power-path LiPo charger, allowing USB-powered operation while charging and battery-backed operation when USB is removed.
- 3.3 V buck regulator for ESP32, RS485 transceiver, status logic, and humidity sensor.
- 12 V boost regulator for the external ultrasonic RS485 flow sensor.
- ESP32-S3-WROOM-1-N16R8 WiFi module with EN reset network, BOOT button, UART programming header, and boot strap support.
- MAX3485 3.3 V half-duplex RS485 interface with external 4-position sensor terminal block.
- SHT31-DIS I2C humidity/temperature sensor with I2C pull-ups and local decoupling.
- Status LEDs for power, WiFi, and flow activity.
Main Components
Table
| Block | Designators | Function |
|---|---|---|
| USB-C input | J1, R1, R2, F1, D1, C1 | 5 V USB-C sink input, CC Rd resistors, fuse, VBUS TVS, input bulk cap |
| Battery charger / power path | U5, J4, R15-R21, C11-C13 | BQ24074 USB LiPo charger and SYS rail power path |
| 3.3 V regulator | U4, L1, R8, R9, C6-C8 | LTC3406B 5 V/SYS to 3.3 V buck regulator |
| 12 V sensor supply | U3, L2, D3, R10, R11, C9, C10 | LM27313 boost converter for external ultrasonic sensor |
| WiFi MCU | U1, R3-R5, C2-C4, SW1, SW2 | ESP32-S3 module, reset/boot network, local decoupling |
| RS485 sensor interface | U2, J2, R6, R7, D2, C5 | MAX3485 transceiver, termination, TVS, sensor connector |
| Humidity/temperature | U6, R22, R23, C14 | SHT31-DIS I2C humidity/temperature sensor |
| Indicators | D4-D6, R12-R14 | Power, WiFi, and flow LEDs |
| Programming | J3 | UART/programming access |
Power Tree
Text
USB-C VBUS -> F1 -> USB_5V_PROTECTED -> BQ24074 IN BQ24074 BAT -> JST-PH LiPo battery connector BQ24074 OUT/SYS -> SYS_PWR SYS_PWR -> LTC3406B -> 3V3 SYS_PWR -> LM27313 -> 12V_SENSOR 3V3 -> ESP32-S3, MAX3485, SHT31, status pull-ups 12V_SENSOR -> external ultrasonic RS485 flow sensor connector
Battery / Charging Notes
- BQ24074 fast charge current is set by R15 = 1.13 kOhm, approximately 800 mA per datasheet equation.
- BQ24074 input current limit is set by R16 = 1.18 kOhm, approximately 1.3 A when EN2=1 and EN1=0.
- BQ24074 termination current is set by R17 = 4.12 kOhm, approximately 110 mA.
- TS is tied valid with R18 = 10 kOhm to GND because no pack thermistor connector was specified.
- CE is pulled low through R19 to enable charging.
- CHG and PGOOD are pulled up to 3.3 V through R20/R21 and routed to ESP32 GPIOs.
External Sensor Interface
J2 is assigned as:
- J2 P1: 12V_SENSOR
- J2 P2: GND
- J2 P3: RS485_A
- J2 P4: RS485_B
The exact ultrasonic sensor model/register map was not supplied. Firmware should implement the selected sensor's RS485 protocol, likely Modbus RTU.
Validation Status
- Electrical rule review for ERC-related checks returned no errors/warnings.
- Full design review reports airwires because the PCB has not been placed or routed yet; this is expected at schematic-only stage.
- Layout/routing has not been started because schematic completion is the checkpoint before PCB layout.
Scope Implemented
Main Components
Power Tree
Battery / Charging Notes
External Sensor Interface
Validation Status
