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docs(esp32p4): correct USB CDC warning — only CDC_ON_BOOT is toxic #12

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Merged
zackees merged 1 commit into from
Jun 20, 2026
Merged

docs(esp32p4): correct USB CDC warning — only CDC_ON_BOOT is toxic #12

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12 changes: 9 additions & 3 deletions platforms/platformio.esp32p4.ini
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Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,15 @@ board_build.partitions = huge_app.csv
; stalls during execution, silently corrupting LED protocol timing.
; See FastLED src/platforms/esp/32/drivers/parlio/ for the canonical chipset list.
;
; Do NOT add -DARDUINO_USB_CDC_ON_BOOT=1 or -DARDUINO_USB_MODE=1 here. They
; wire Serial to the USB-CDC interface, which only enumerates when a USB host
; is connected — boards powered from a wall adapter then hang in setup().
; Do NOT add -DARDUINO_USB_CDC_ON_BOOT=1 here. It wires Serial to the USB-CDC
; interface, which only enumerates when a USB host is connected — sketches
; that touch Serial in setup() (especially `while (!Serial) {}`) then hang
; when the board is powered from a wall adapter instead of a PC.
;
; ARDUINO_USB_MODE selects HWCDC vs TinyUSB *when CDC-on-boot is enabled*;
; it has no effect on Serial routing while CDC_ON_BOOT=0, so we leave it
; unset here. P4's upstream default is 0 (TinyUSB); C3/C5/C6/H2 force it to
; 1 (HWCDC) via platform.txt.
build_flags =
-DCONFIG_PARLIO_TX_ISR_HANDLER_IN_IRAM=1
-DCONFIG_PARLIO_TX_ISR_CACHE_SAFE=1
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