uwb tag

UWB tag carrier, rev A

The badge the cleaner wears. A Seeed XIAO ESP32S3 Plus is reflowed onto a carrier board. The carrier holds a Qorvo DWM3000 UWB module (antenna at the board edge), an ST LSM6DSO motion sensor, a side-press shift button and a vibration-motor driver. A 1S LiPo on the underside is charged by the XIAO from its USB-C, in a dock.

Board	58 × 26 mm, 2 layers, 1.6 mm FR-4, 1 mm corner radius
Rules	0.25 mm tracks, 0.15 mm clearance (needed for the IMU's 0.5 mm-pitch pads), 0.7/0.3 mm vias (0.2 mm annular ring; rule minimum 0.18 mm), 0.5 mm hole-to-hole, 0.3 mm copper-to-edge. All inside JLCPCB/PCBWay standard capability.
Tool	KiCad 7 (opens in 7, 8 or 9). Self-contained: kicad/libs/ holds the stock parts used.
Checks	KiCad DRC, run locally: 0 violations, 0 unconnected pads, 0 footprint errors. Closest drill-to-drill gap: 0.64 mm. ERC: run in KiCad or via BoardRepo (KiCad 7's CLI has no ERC).

Pin use (XIAO ESP32S3 Plus)

XIAO pin	GPIO	Net	Why this pin
D0	1	BTN (shift button, 100k pull-up, 100 nF debounce)	RTC GPIO: wakes from deep sleep
D1	2	IMU_INT1	RTC GPIO: wake on motion
D2	3	VIB_EN (motor FET gate)	100k gate pull-down keeps the strap pin low at boot
D3	4	UWB_IRQ (100k pull-down)
D4 / D5	5 / 6	I2C SDA / SCL (4.7k pull-ups)	XIAO default I2C
D7	44 (UART0 RX)	UWB_RSTn	An input during boot, so the DWM3000's reset is never driven high (Qorvo)
D8 / D9 / D10	7 / 8 / 9	UWB SCK / MISO / MOSI	XIAO default SPI
D17	13	UWB_CS (also wakes the DW3000)	Plus edge pad
D19	11	UWB_WAKEUP	Plus edge pad
D16	10	Not connected	The Plus measures battery voltage itself on GPIO10 (ADC_BAT)
VBAT pad (underside)	–	VBAT, to J1	The XIAO charges the cell at 100 mA
D14 / D15 / D6	41 / 42 / 43	LED_R / LED_G / LED_B (external RGB LED, via 1 kΩ)	D6 is UART TX, so blue flickers at boot
D11–D13, D18	–	Free	Console runs over USB

Other parts

• U2, DWM3000: wiring and decoupling identical to the anchor (C1–C3, R1).
• U3, LSM6DSO: in I2C mode (CS high) at address 0x6A (SA0 low). Auxiliary I2C pins SDx/SCx are tied to GND; OCS_Aux, SDO_Aux and INT2 are left open.
• Motor: Q1 (AO3400A) low-side switch, D1 (B5819WS) flyback diode, C6 10 µF bulk, R5 100 Ω gate series, R6 100k gate pull-down. The motor's wire leads go to J2 (bottom).
• Battery: 1S LiPo, which must have its own protection PCM. Wire leads go to J1 (bottom); + is marked.
• External RGB status LED, J3: 5-pin 2.54 mm through-hole connector at the bottom edge: 1 R, 2 G, 3 B, 4 +3V3, 5 GND. The 1 kΩ resistors (R7–R9, 0402) give about 1 mA per colour, to save battery. For a common-anode LED, use pin 4 and drive the pins low; for a common-cathode LED, use pin 5 and drive them high.
• No test pads: DWM3000 GPIO0–7 are unused on the tag. The anchor board carries the GPIO0–3 debug pads.

Layout

• The XIAO's USB-C is flush with the left edge for the charging dock. The DWM3000 antenna is at the right edge, with Qorvo's copper keep-out on both layers. The XIAO's Wi-Fi uses its own U.FL antenna, so no keep-out is needed under it.
• Signals run mostly on top (about 560 mm) against about 220 mm of short crossovers on the bottom. The bottom is a near-solid ground plane, stitched with about 60 vias.
• UWB_RSTn is hand-routed along the top edge. Everything else was autorouted with Freerouting.

Building it

1. PCB + assembly: fab/ Gerbers + drill, fab/uwb_tag-bom-jlc.csv, fab/uwb_tag-cpl-jlc.csv. D1, SW1 and U3 have no LCSC number filled in, so pick stock or consign them.
2. XIAO: paste on all U1 pads, including the underside VBAT/GND pads. Seat the XIAO with its USB-C at the edge marked USB-C, then reflow (hot plate or hot air). An iron alone can't reach the battery pads.
3. By hand: LiPo leads to J1 and motor leads to J2, on the bottom. Stick the XIAO's U.FL antenna to the enclosure lid, away from the UWB end. See fab/hand-fit-parts.csv.

Before ordering: verify

• XIAO footprint: copied from Seeed's official KiCad library (XIAO-ESP32-S3-Plus-SMD, CC BY-SA 4.0). Print the top layer 1:1 and check it against a module.
• LSM6DSO unused-pin handling (SDx/SCx to GND, OCS_Aux/SDO_Aux open): check against ST's datasheet.
• DWM3000 footprint: KiCad's DWM1000 land pattern (Qorvo: pin- and pitch-compatible). Not compared against the DWM3000 drawing.
• LCSC numbers: confirm stock.
• Thickness: the cell sits under the XIAO end. Allow board + battery + about 3 mm for the XIAO when sizing the enclosure.

Regenerating

Run tools/run_all.sh. It builds the libraries and the schematic, then places parts, hand-routes RSTn and autoroutes the rest. It finishes with ground stitching and island bridging, DRC, and the fab outputs. It needs KiCad 7, Java, Xvfb and Freerouting 1.9.