Barometer
It works out the altitude too
Page 38 reads a BMP280 (I2C 0x76, or 0x77 when ADDR is pulled high) and shows pressure in hPa, an altitude derived from the standard atmosphere, a short-term trend, and the health score at the bottom.
★ The compensation maths runs entirely in int64. The vendor formula contains terms like `(int32_t)t_fine * 47`; at 32 bits those overflow in the low-temperature range and the temperature readout turns into garbage — which looks like a dead part but is really an arithmetic overflow.
On-screen interface
A recreation of this page on the 2.41-inch AMOLED display (600 × 450). Actual interaction and layout follow the latest firmware.
Key capabilities
Pressure + altitude
Both on screen, so you never apply the formula by hand.
Trend
A short trend bar shows whether pressure is climbing or falling.
int64 compensation
Full 64-bit maths, so no garbage readouts in the cold.
Health score
Reply, ID, plausibility and stability, scored separately.
Technical specs
Typical scenarios
Weather trend
Falling pressure usually means weather turning; page 41 states it plainly.
Floor or altitude
A rough sense of which floor the box is on, or relative height outdoors.
Related commands
page 38 Open the barometer page bmp Read pressure, temperature and altitude once bmp on | off Start or stop periodic sampling
- Compensation must be int64; 32-bit overflows in the cold and corrupts the readout.
- Pressure tracks weather and altitude — 3–5 hPa across a day is normal.
- Keep the module away from air-conditioner outlets and fans; airflow makes it twitch.