BME280

The BME280 adds a humidity element; everything else is essentially shared. Both cover 300 to 1100 hPa with ±1 hPa absolute and ±0.12 hPa relative accuracy, both run from 1.71 V to 3.6 V with I2C to 3.4 MHz and SPI to 10 MHz, and the register map is compatible. The differences are the humidity channel (0 to 100 percent RH, ±3 percent RH), the chip ID (0x60 for BME280, 0x58 for BMP280), a slightly larger 2.5 × 2.5 mm package versus 2.0 × 2.5 mm, and 3.6 µA versus 2.7 µA at 1 Hz. If you do not need humidity, the BMP280 is cheaper and smaller.

You almost certainly received BMP280 dies remarked as BME280 — the single most common counterfeit in this family. Read register 0xD0: 0x60 confirms a real BME280, 0x58 means BMP280 silicon, and any other value points to a clone fab. Also confirm the humidity trimming block at 0xA1 and 0xE1 to 0xE7 is populated and that the humidity register changes when you breathe on the part. Reject the lot; a remarked BMP280 will never produce humidity data regardless of firmware.

Address is 0x76 with SDO grounded or 0x77 with SDO tied to VDDIO — this is the same address pair as the BMP280 and BMP180, so scan the bus to confirm which is populated. The two classic failure modes are a floating SDO pin, which makes the address undefined, and CSB not held at VDDIO: CSB is the interface selector, and once it has been pulled low even briefly the device locks into SPI mode until the next power-on reset. Add 2.2 kΩ to 10 kΩ pull-ups on SDA and SCL to the VDDIO rail.

Use I2C for a shared bus, minimum pins and battery nodes; use SPI when you need the highest throughput, the shortest conversion latency or you are operating in a noisy environment where open-drain edges are marginal. For SPI, tie CSB to a GPIO, SDO to MISO, SDI to MOSI and SCK to SCLK, and use mode 00 or mode 11. Bosch supports 3-wire SPI as well, which saves a pin at the cost of driver complexity. Note that SPI is limited to 10 MHz while I2C reaches 3.4 MHz in high-speed mode — both are far faster than the sensor can convert.

Use the barometric formula with the local sea-level reference: altitude = 44330 × (1 − (P / P0)^0.1903) metres, where P is the compensated reading and P0 your calibrated sea-level pressure. The BME280's ±0.12 hPa relative accuracy corresponds to roughly ±1 m of altitude step resolution, which is what makes floor detection practical, but absolute altitude still depends on how fresh your P0 reference is — weather can move sea-level pressure by several hPa per day. For a variometer, high-pass the pressure or differentiate it, and enable the IIR filter (coefficient 4 or 16) to suppress door-slam transients.

For weather monitoring Bosch recommends forced mode with humidity oversampling ×1, pressure oversampling ×1, temperature oversampling ×1, IIR filter off and a 1 s standby — that is the 3.6 µA figure. For humidity sensing use normal mode with humidity ×4, pressure ×16, temperature ×2, IIR ×16 and 0.5 ms standby. Keep self-heating in mind: running continuous high-oversampling conversions warms the die slightly and depresses the humidity reading by a fraction of a percent, so forced mode is preferable for accuracy as well as for battery life.

The Sensirion SHT30/SHT31 family is the better pure hygrometer: ±2 percent RH typical accuracy, faster response and better long-term drift, and it comes in a vented lid option. The BME280 wins on integration and cost — you get calibrated pressure and temperature for free, plus a ±1 m relative altitude capability that the SHT3x does not offer. Choose BME280 for multi-parameter nodes, choose SHT3x or SHT85 when humidity is the parameter that matters. If you also need gas or VOC sensing, look at the BME680.

MOQ is 1 reel (10,000 pcs) for LGA-8 tape-and-reel production builds, or 100 pcs on cut tape for prototyping and small batches. Shenzhen stock ships in 1-3 business days; Bosch Sensortec authorized channel replenishment is typically 6-12 weeks. Every lot we ship can be supplied with chip-ID verification records and a certificate of conformance on request.