I2C Pressure Sensor

Other Hardware Sensors
30

This part does not what it should do:

while(Wire.available() < 4 );          // Check for data from slave
   {   
...

The ';' after the while closes the while statement.
The '{' is not used. But you don't get an error message.

Could you do this:

// while(Wire.available() < 4 );
if( Wire.available() == 4)      // check if actually 4 bytes are received.
...