Add Serial/USB foot-gun warnings for AVR (ATmega32U4), RP2040, and Teensy#6
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zackees merged 2 commits intocopilot/add-unit-test-cdc-boot-warningfrom Mar 26, 2026
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…ensy platforms Agent-Logs-Url: https://github.com/FastLED/fbuild/sessions/e6b79394-5328-481e-99c8-df11afbe5019 Co-authored-by: zackees <6856673+zackees@users.noreply.github.com>
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[WIP] List print and boot related issues for ESP/AVR/NRF/Teensy/RP
Add Serial/USB foot-gun warnings for AVR (ATmega32U4), RP2040, and Teensy
Mar 26, 2026
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Follow-up to #4 (ESP32
ARDUINO_USB_CDC_ON_BOOT=1warning). Three more platforms silently routeSerial.print()over USB CDC, causing hangs or stalls when no USB host is present at boot.New warnings
Serialis always USB CDCSerialto USB CDCUSB_SERIALmode routesSerialover USBImplementation
orchestrator_avr.py—_check_native_usb_cdc(board_id, mcu): fires whenmcu.lower() == "atmega32u4"; no opt-out (USB is hardwired on this MCU).orchestrator_rp2040.py—_check_usb_serial_default(board_id, build_flags): fires for all RP2040 builds; suppressed by-DPICO_STDIO_USB=0inbuild_flags.orchestrator_teensy.py—_check_usb_serial_mode(board_id, build_flags, platform_config): resolves the effective USB mode using last-definition-wins across platform-config defines + userbuild_flags; fires only when the resolved mode isUSB_SERIAL. Switching to-DUSB_SERIAL_HID,-DUSB_MIDI, etc. suppresses it.Tests
32 new unit tests across three files following the same pattern as
test_cdc_on_boot_warning.py, covering warning fires, board-id in message, opt-out paths, and last-definition-wins semantics.Original prompt
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