BMV080 is a low-power, low-cost PM1, PM2.5, and PM10 sensor module with I2C and SPI interfaces that sells for just $29.90.
The I2CKeyPad8x8 library implements the reading of a 8x8 keypad by means of a PCF8575. Smaller keypads, meaning less columns or rows (e.g. 5x4) can be read with it too. Sometimes you need to control ...