The GY-21P is an interesting module in that it combines a BMP280 sensor and an SI7021 sensor. The on-board BMP280+SI7021 sensor measures atmospheric pressure from 30kPa to 110kPa as well as relative humidity and temperature. BMP280 Pressure range: 300-1100 hPa (9000 meters above sea level at -500m) Relative accuracy (at 950 – 1050 hPa at … Continue reading Arduino and GY-21P module example