title: reading from PCA 9554 (i2c) in Arduino
body: <p>I am trying to read data from a PCA9554 in arduino.
  The hard ware setup is simple: all 3 address line of the PCA9554 is connected to high (+5 v), so the address of this device is 0x27.
  The code that I am using to read the value is as follow:</p>
  
  <pre><code> uint8_t i2cr8(uint8_t dev, uint8_t addr)
   {
        uint8_t val=-1;
        Wire.requestFrom(dev,(uint8_t)1);
        if(Wire.available()) {
            val = Wire.read();
         }
         return val;
    }
  </code></pre>
  
  <p>but it always read 0. </p>
  
  <p>What is wrong with this code? </p>
  
  <p>I think there is no error with hardware as I can read from other devices on I2C bus.</p>