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BMP581 ("Pressure Sensor") Molecule — Hardware Reference

Tiny (~8×8 mm) 4-corner-pin breakout for the Bosch BMP581 barometric pressure sensor. Upstream folder is named generically (Pressure Sensor) — the IC is explicitly a BMP581 (per BOM and silk).

Source: adom-inc/bosch-molecules/Pressure Sensor — imported 2026-04-17
KiCad project: Pressure Sensor.kicad_pro
Wiki page: molecules/pressure-sensor-876000 — silk/title is "Pressure Sensor" (generic — import stub from 2026-03-02), but the IC is explicitly a BMP581
Board: 4 corner through-hole mount-pins + 1 side castellation for INT, single-sided assembly
IC: BMP581 (Bosch QFN-10, 2.0 × 2.0 × 0.75 mm, U1)

Component summary (from `Pressure Sensor/production/bom.csv`)

Ref	Part	LCSC	Function
U1	BMP581	C5362283	Barometric pressure sensor
C1	100 nF 0402	C1525	VDD decoupling
D1	LED 0603	C2290	Power indicator
R5	510 Ω 0402	C25123	LED current limit
R1	10 kΩ 0402	C25744	SDO pull-up → 3.3 V (→ address 0x47)
R3	10 kΩ 0402	C25744	CSB pull-up → 3.3 V (→ I²C mode)
R2	10 kΩ 0402	—	DNP (would pull SDO → GND for address 0x46)
R4	10 kΩ 0402	—	DNP (would pull CSB → GND for SPI mode)

R1/R2 and R3/R4 are a configure-once DNP pair. On the shipped board, R1 and R3 are populated; R2 and R4 are not. Address and interface are therefore hard-set — no jumpers, no user action.

External contact map

Ref	Silk	Net	Kind	Role
MP101	`3.3V`	`+3.3V`	mount	VDD / VDDIO (shared)
MP102	`GND`	`GND`	mount	Ground
MP103	`SCL`	`SCK`	mount	I²C SCL (silk uses I²C naming; net uses SPI naming — same pad, dual-protocol)
MP104	`SDA`	`SDI`	mount	I²C SDA (silk uses I²C naming; net uses SPI naming — same pad, dual-protocol)
MC101	`INT`	`INT`	contact	Interrupt output

I²C address (fixed via R1/R2 DNP pair)

R-pair populated	SDO tied to	I²C address
R1 fitted, R2 DNP (as shipped)	+3.3 V	0x47 (demo firmware target ✓)
R2 fitted, R1 DNP	GND	0x46

The demo firmware expects 0x47 — no action needed.

Interface mode (fixed via R3/R4 DNP pair)

R-pair populated	CSB tied to	Mode
R3 fitted, R4 DNP (as shipped)	+3.3 V	I²C (demo target ✓)
R4 fitted, R3 DNP	GND	SPI (4-wire)

Again — no action needed on the shipped board.

Power

Rail	Voltage	Source
VDD / VDDIO	1.71–3.6 V (3.3 V in demo)	Host via MP101

Single rail (VDD = VDDIO on this board). Typical active current 70 µA in normal mode — lowest draw of any sensor in the demo. Rail headroom is a non-issue.

Interrupt

MC101 (silk INT) is the BMP581's programmable interrupt output. Default polarity / drive mode is set at init (firmware/sensors/bmp581.c). Leave floating if unused.

Wiring to the Stationary RM2 I²C bus

BMP581 MP101 (3.3V) ──── RM2 +3V3
BMP581 MP102 (GND)  ──── RM2 GND
BMP581 MP104 (SDA)  ──── RM2 GPIO4 (I²C0 SDA)
BMP581 MP103 (SCL)  ──── RM2 GPIO5 (I²C0 SCL)
BMP581 MC101 (INT)  ──── (optional)

Gotchas for firmware bring-up

No user-configurable jumpers on this board. Address is 0x47, mode is I²C — both set by populated-vs-DNP resistors. If you see a probe NACK at 0x47, the chip is either not powered, not connected to the bus, or a rework has changed R1/R2 or R3/R4 state. Check with a multimeter on SDO/CSB before debugging further.
4.7 kΩ I²C pull-ups are off-board (provided by the stationary RM2 carrier).
70 µA typical — the BMP581 is effectively a rounding error on the 3.3 V rail's budget.
Silk pin labels use I²C names (SDA, SCL), but the underlying nets are named in SPI terms (SDI, SCK) because the QFN-10 pads are dual-protocol. Don't let that confuse you.

Pressure Sensor