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Accept USB BOOTSEL reboot on the UART firmware

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The regular firmware now answers the EP0 vendor INFO and BOOTSEL reboot
requests with the AIO wire protocol, so switch-pico-config reboot bootsel
works when the Pico's USB side is on a PC. Wire constants move to
usb_management_protocol.h; other operations stall.
This commit is contained in:
Joey Yakimowich-Payne 2026-09-22 10:59:29 -06:00
commit 8db720fb9a
16 changed files with 489 additions and 67 deletions
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README.md
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@ -2649,24 +2649,36 @@ The firmware acknowledges the endpoint-zero request, waits 50 ms, and then
calls the Pico ROM `reset_usb_boot()` entry point. Physical BOOTSEL remains the
fallback if the firmware or USB management path is unavailable.
The regular UART firmware has the same shortcut over its serial link. The
host sends the command frame `0xAA 0xFE 0x08 0x01 "BOOTSEL" checksum`; the
firmware verifies the checksum and magic, flushes UART TX, and calls
`reset_usb_boot()`. Line noise or a misframed report cannot trigger it. The
Pico can stay plugged into the Switch or a PC; only the UART adapter needs to
be connected to the host:
The regular UART firmware has the same shortcut, reachable two ways:
- **Over USB** (Pico's USB plugged into the PC, no serial adapter needed): the
firmware answers the same EP0 vendor `INFO` and `BOOTSEL reboot` requests as
the AIO, so `switch-pico-config reboot bootsel` works unchanged. Every other
management operation is stalled; `status`, profiles and configuration are
AIO-only. The Switch never issues vendor requests, so the handler is
invisible to the console.
- **Over UART** (Pico can stay on the Switch or a PC; only the serial adapter
is on the host): the host sends `0xAA 0xFE 0x08 0x01 "BOOTSEL" checksum`;
the firmware verifies checksum and magic, flushes UART TX, and calls
`reset_usb_boot()`. Line noise or a misframed report cannot trigger it.
```sh
# One-off reboot, then flash the published image
# USB side on the PC
uv run switch-pico-config reboot bootsel
picotool load -v -x firmware/switch-pico.uf2
# UART adapter on the PC
uv run controller-uart-bridge --reboot-bootsel /dev/ttyUSB0
picotool load -v -x firmware/switch-pico.uf2
# Build, publish, reboot the running Pico and flash in one step
# Build, publish, reboot the running Pico over UART and flash in one step
uv run python build.py --uart-port /dev/ttyUSB0
```
Firmware from before this command ignores the frame; hold BOOTSEL while
replugging once to install a build that has it.
Either way the RPI-RP2 loader appears on whichever USB host the Pico's own
USB port is connected to, so flashing needs that port on the PC. Firmware from
before these commands ignores both; hold BOOTSEL while replugging once to
install a build that has them.
Flash alternatives: bootsel + drag-drop or `picotool load`.
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