Short answer

ESP32 keeps brownout resetting on Wi-Fi start. What is wrong?

  • Brownout on Wi-Fi TX is almost always power delivery: USB cable, thin 3.3 V rail, or a regulator that cannot handle the current spike.
  • Measure 3.3 V at the module during association, not only at the bench supply. A soft cable drops voltage only under load.
  • Add bulk capacitance close to the ESP32 power pins. Decoupling far away on the USB connector does not help the RF pulse.
  • Do not blame the Station example first. Fix the rail, then re-test join.

中文

短答

ESP32 一开 Wi-Fi 就欠压复位，先查什么？

  • Wi-Fi 发射时欠压，多半是供电：USB 线太细、3.3 V 轨软、稳压扛不住电流尖峰。
  • 要在模组脚上测关联瞬间的 3.3 V，不要只看电源表头。软线只在负载时掉压。
  • 大电容要靠近 ESP32 电源脚。电容只焊在 USB 口附近对射频脉冲没用。
  • 先别怪 Station 例程。电源轨稳了再测联网。