• use CH341T to hook DEBUG port (SWD path) — postponed
• answer datasheet/README Q's
• basic test — basic-test/ blinks LED + prints measured clocks over USB serial
• basic test board-2 — OK
• hook 1.28" 240x240 GC9A01-based round display via SPI

This board's USB port handles power, BOOTSEL flashing, and USB CDC serial — all over one data-capable cable.

After flashing:

1. ls /dev/cu.usbmodem*
2. screen /dev/cu.usbmodem<Tab> 115200.

See SDK.md