USB-C and serial

One USB-C port, two possible owners, and a slide switch to pick between them.

Port: USB-C 2.0, 16P
Bridge: CH340C (U3)
Selector: S1 · DPDT
Native USB: GPIO19 / GPIO20

J1 is the only data port on the badge, and S1 decides who gets it. The connector's D+/D− pair — ESD-protected by D2, with 5K1 CC resistors R4/R5 — routes either to the CH340C USB-serial bridge or straight to the ESP32-S3's native USB pins through 22 Ω series resistors R29/R30.

The two paths are mutually exclusive. Flip S1 toward UART and you get a classic serial port with auto-programming: Q1 and Q2 translate the CH340C's DTR and RTS into GPIO0 and EN, so esptool can reset the chip into download mode without anyone touching a button. Flip it toward HID and the ESP32 enumerates directly — USB CDC, TinyUSB, DFU, HID.

BOOT1 and RST1 are the manual version of the same thing: hold BOOT1, tap RST1, release BOOT1. UART0 on GPIO43/44 stays wired to the CH340C throughout, and the firmware mirrors its log to both UART0 and the USB CDC port so a board can be diagnosed over whichever one you have.

Pins

Pin	Net	Role	Function
GPIO19	ED−	USB D−	Native USB D−, through 22 Ω R29 to S1.
GPIO20	ED+	USB D+	Native USB D+, through 22 Ω R30 to S1.
GPIO43	TX0	UART0 TX	UART0 TX to the CH340C for upload and serial monitor.
GPIO44	RX0	UART0 RX	UART0 RX from the CH340C via 220 Ω series R16.

Parts

J1 USB-C receptacle, USB 2.0 16P Power in and the single data pair
S1 MST-22D18G2 DPDT slide switch — routes D+/D− to the CH340C or to native USB
U3 CH340C USB-to-UART bridge on UART0
D2 SRV05-4 ESD protection on the USB data pair
Q1 / Q2 SS8050 Auto-program circuit — DTR → GPIO0, RTS → EN
BOOT1 / RST1 B3U-1000P Manual download-mode and reset buttons

Notes

Native USB and CH340C serial cannot be active at the same time — the switch is the arbiter.
The USB HID mouse path in the test firmware only compiles under the USB-OTG / TinyUSB USB mode; the default Hardware CDC build reports “HID OFF” and skips it.