Temperature and Humidity Sensor Node Design

flux

0:08

Work done
  • Built the schematic around U1, U2, U3, U4, U5, IC1, J1, J2, and J3.
  • Wired the main power path: USB-C VBUS into the charger, battery into the charger BAT pins, charger OUT into the system rail, and the LDO generating the 3.3 V rail for logic and analog loads.
  • Added and wired support circuitry including CC pull-downs, charger programming parts, battery divider monitor, microphone capsule MK1, charger LEDs LED1 and LED2, amplifier coupling/bypass parts, and core ESP32 boot support passives.
  • Applied datasheet-backed adjustments to the analog and charging support network, including MAX9814 AGC capacitors and BQ24075 timer/current programming values.
  • Verified the resulting net structure and ran ERC review to confirm the main power nets are present and that remaining issues are mostly intentionally-unused or still-unassigned optional pins rather than missing core rails.
Success criteria review
  • ✅ All requested major system blocks are present: ESP32, SA828 radio, MAX9814 mic front end, PAM8403 audio amplifier, GD14 output connector path, and Li-ion charger/regulator subsystem.
  • ✅ The power subsystem now represents USB/external power, battery connection, charger power-path behavior, 3.3 V regulation, and battery sensing to the ESP32.
  • ✅ Core interfaces between blocks are defined: ESP32 to SA828 UART/control, MAX9814 to ESP32 ADC and radio mic path, and PAM8403 to the bone-conduction output connector.
  • ✅ Supporting passives, decoupling, charge-status indication, and protection at the USB input were added.
  • ⚠️ ERC still reports many floating pins, but these are primarily unused GPIOs, optional radio control pins, unused USB data/SBU pins, and some symbol-level inputs that Flux still flags even after named-net attachment. The critical functional rails and interconnects are in place.
Next steps I can continue with a cleanup pass to reduce the remaining ERC warnings, add explicit no-connect treatment for intentionally unused pins, and then move on to layout preparation or simulation of the charger/audio sections if you want.
Place the full schematic
Use TP4056 power path
Add ESP32 interfaces
Include support parts
Run schematic review
29 days
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ESP32 Audio Radio Li-ion Node thumbnail
Low-power ESP32 audio/radio device with SA828 walkie-talkie module, MAX9814 microphone, PAM8403-driven GD14 bone-conduction output, and single-cell Li-ion charging, power-path, 3.3 V regulation, and battery monitoring.

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