KiCad Export

flux

Sorry—my previous answer was incorrect. Flux does not currently offer a native KiCad .kicad_pcb export.
In Flux’s Export menu, the PCB fabrication option is Manufacturing Files (Gerbers, etc.). These Gerber/drill files can be viewed in KiCad’s Gerber Viewer, but they are not an editable KiCad PCB project.
A

amirghasemi21

the PS/SYNC (U4 pin 7) on the 3V3 net? or should it be on GND?

flux

For this battery-powered sensor, U4 pin 7 (PS/SYNC) should normally connect to GND.
  • GND/LOW: enables power-save mode, improving light-load and ESP32 sleep efficiency.
  • 3V3/HIGH: forces PWM operation, giving lower ripple but consuming more standby current.
  • It should not normally be powered from U4’s own 3V3 output, because that output is unavailable during startup.
Use 3V3 only if you deliberately need forced-PWM operation; otherwise connect pin 7 directly to GND.
A

amirghasemi21

check the current schematic, how is it now?

flux

I’ll inspect U4 pin 7’s current net and verify the surrounding TPS63001 connections.

flux

Currently, U4 pin 7 (PS/SYNC) is connected to the 3V3 net, along with VOUT and FB. That selects forced-PWM operation.
For this battery sensor, I recommend moving PS/SYNC to GND to enable power-save mode and reduce sleep/standby consumption. U4’s GND, PGND, and exposed pad are already connected to GND.
Fix and verify regulator
Move PS/SYNC to GND
Verify regulator wiring
Run schematic review
Explain power-save mode
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Files

Schematic

Layout

Preview

D1
U1
U2
J1
U3
F1
L3
Inductance
2.2uH
D2
J2
Buck-Boost Regulator
C1
Capacitance
1uF
C10
Capacitance
1uF
R10
Resistance
10kΩ
R2
Resistance
5.1kΩ
C3
Capacitance
4.7uF
R13
Resistance
1.0MΩ
R9
Resistance
10kΩ
R11
Resistance
10kΩ
R6
Resistance
46.4kΩ
R7
Resistance
100Ω
C2
Capacitance
4.7uF
R5
Resistance
4.12kΩ
R15
Resistance
10kΩ
R14
Resistance
1.0kΩ
R3
Resistance
1.13kΩ
SW1
R4
Resistance
1.18kΩ
R8
Resistance
10kΩ
R1
Resistance
5.1kΩ
C7
Capacitance
0.1uF
C11
Capacitance
4.7uF
R12
Resistance
1.0MΩ
C5
Capacitance
10uF
C6
Capacitance
10uF
SW2
C9
Capacitance
0.1uF
C8
Capacitance
22uF
C4
Capacitance
10uF
Board Bring-Up Plan — ESP32-C6 CO2 Sensor
Prerequisites
  • Equipment: multimeter, current-limited USB supply, oscilloscope if available, USB-C cable, PlatformIO host.
  • Battery: protected 1-cell LiPo, nominal 3.7 V, connector polarity verified before plugging into J2.
1. Visual Inspection
  • Inspect U3 BQ24074, U4 TPS63001, U1 ESP32-C6-WROOM-1, U2 SCD41, J1 USB-C, J2 LiPo connector, D1 USB ESD, F1 PTC.
  • Verify no bridges around U3/U4 QFN pins and USB-C pads.
2. Power Rail Verification

Table

RailSourceExpectedMeasure AtCurrent LimitPass Criteria
USB_VBUS_RAWJ1 VBUS before F15.0 VJ1/F1 pin 1100 mA first power4.75-5.25 V
VBUS_PROTF1 output5.0 V minus fuse dropU3 IN/C1100 mA first powerwithin 0.2 V of USB_VBUS_RAW at light load
VBATJ2 / U3 BAT3.0-4.2 V batteryJ2 P1/C2battery limitedcorrect polarity, no short
SYSU3 OUTbattery or USB system railC3/U4 VIN100 mA first power~VBAT on battery, ~4.4 V on USB
3V3U4 VOUT3.3 VC5/C6/U1 pin 2100 mA first power3.14-3.47 V
Procedure: check resistance from 3V3, SYS, VBAT, and VBUS_PROT to GND before power. Power from USB first with no battery, then repeat with battery installed.
3. Critical Signals

Table

SignalExpected IdleNotes
ESP_ENHigh, near 3.3 VSW1 pulls low for reset
ESP_BOOT / IO9High, near 3.3 VSW2 pulls low for bootloader
I2C_SDA / I2C_SCLHigh, near 3.3 V idlePulled up by R10/R11
USB_D_PLUS / USB_D_MINUSUSB activity during enumerationRoute/check as differential pair in layout
VBAT_SENSEVBAT/24.2 V battery gives ~2.1 V ADC input
4. Programming and Functional Tests
  1. Connect USB-C and verify 3V3 before flashing.
  2. Flash the firmware from the Firmware Starter file.
  3. Confirm USB serial enumeration and boot logs.
  4. Run I2C/SCD41 read test; expect CO2 in plausible indoor range after sensor warm-up.
  5. Confirm status LED D2 toggles during successful readings.
  6. Confirm ADC battery reading roughly equals measured VBAT.
  7. Verify LiPo charging behavior with a current-limited USB source and monitor U3 temperature.
5. Pass/Fail Summary

Table

SectionResultNotes
Visual inspection[ ] Pass / [ ] Fail
Power rails[ ] Pass / [ ] Fail
USB/programming[ ] Pass / [ ] Fail
SCD41 sensing[ ] Pass / [ ] Fail
Battery charging[ ] Pass / [ ] Fail
Sleep/runtime test[ ] Pass / [ ] Fail
Open Layout Recommendations
  • Add test points for GND, VBUS_PROT, SYS, VBAT, 3V3, ESP_EN, I2C_SDA, I2C_SCL.
  • Keep ESP32-C6 antenna area clear per Espressif module layout guidance.
  • Keep U4 inductor and switching loop compact; place C4/C5/C6 close to U4.

  • Prerequisites

  • 1. Visual Inspection

  • 2. Power Rail Verification

  • 3. Critical Signals

  • 4. Programming and Functional Tests

  • 5. Pass/Fail Summary

  • Open Layout Recommendations