I'm trying to debug an early-boot hang on a Pixel 9a (tegu, bootloader unlocked) and want to capture kernel/init logs over UART, since the device never reaches a state where ADB is available.
I've found documentation for UART debugging on older Pixels (Pixel 2/3/3a XL) using fastboot oem uart enable plus a USB-C breakout board with a 1.8V USB-to-TTL serial adapter on the SBU pins. I haven't been able to find any confirmation of whether the same approach works on tegu, or whether the UART path/electrical setup has changed on the 9-series.
A few specific questions for anyone who's done this on tegu (or a closely related Tensor G4 device):
Does fastboot oem uart enable still exist and work on Pixel 9a?
Are the SBU-pin TX/RX assignments the same as on earlier Pixels, and is the logic level still 1.8V?
Any known gotchas — e.g. UART being silenced after a certain boot stage, baud rate quirks, or things that work on other 9-series models but not tegu?
If anyone has a working capture from a normal boot on tegu, even a short snippet, that would be hugely helpful as a sanity check that my setup is correct.
Happy to share findings back if I get something working.
Thanks.