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(bool)Serial was wrong: HWCDC::isCDC_Connected() and USBCDC::operator bool() only report true once an actual terminal has exchanged data with the port (CDC TX/RX, or DTR/RTS), so the flag stays stuck false after a plain esp_restart() with no monitor attached, even though USB is genuinely powered. Confirmed on real V4.3 hardware: the charging icon vanished after WiFi-toggle reboots and only returned after a manual RST where a tool happened to be talking to the port. Two USB stacks are in play depending on ARDUINO_USB_MODE: - Native USB-Serial-JTAG (HWCDC, V4.3): Serial.isPlugged(), public static, purely SOF-frame-based (USB PHY level). - External USB-OTG via TinyUSB (USBCDC, Wireless Tracker V2): tud_mounted(), reflects real bus enumeration, independent of DTR/RTS. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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What
Overrides isExternalPowered() on ESP32Board to use PHY-level USB detection instead of relying on (bool)Serial.
Why
No ESP32-S3 board in this codebase overrode isExternalPowered() before (confirmed by grep; the base MainBoard default is
return false;), unlike NRF52Board, which has a real VBUS-detect register (no ESP32-S3 equivalent exists). The obvious first attempt, (bool)Serial, is wrong on both USB stacks used in this codebase: HWCDC::isCDC_Connected() and USBCDC::operator bool() only report true once an actual terminal has exchanged data with the port (CDC TX/RX, or DTR/RTS), so the flag stays stuck false after a plain esp_restart() with no monitor attached, even though USB is genuinely powered. Confirmed on real V4.3 hardware: the companion display's charging icon vanished after a WiFi-toggle reboot and only came back after a manual RST where a terminal happened to be talking to the port.How
Two USB stacks are in play depending on ARDUINO_USB_MODE:
Common limitation either way: a dumb charger with no data lines generates no SOF traffic and never enumerates, so it will not be seen as external power; only an active USB host (PC, OTG phone) will.
Testing
Compiled and validated on real hardware for both stacks (Heltec V4.3 and Wireless Tracker V2): the charging icon now reflects actual USB presence across WiFi-toggle reboots and manual resets.
(Generated with Claude Code)