CTL_STATUS_t sht2x_read_user(CTL_HUMIDITY_SENSOR_t *self);
sht2x_read_user reads the user register of the sensor self.
sht2x_read_user returns an extended status code: non-negative values indicate a successful read, and value, of the user register.
sht2x_read_user is thread-safe if the transport member in self is thread-safe. This requires that a mutex is associated with the I2C bus provided when calling sht2x_initialize_i2c.