Before soldering an I2C device to a board, always verify that the device is placed in the correct orientation. An I2C device continuously sends NACKs back to the controller if the device is incorrectly soldered onto a PCB. Soldering a device in an incorrect orientation can also damage the device whenever power is applied to the circuit. When verifying if a device has been soldered onto a PCB properly, look for two things: a package marking, and a footprint marking. These markings on the package and footprint are created to help the user match the pin locations of the package to the pin locations of the footprint.

Generally, a package marking is placed directly over pin 1 of the package (see Figure 2-5). The shape of the marking can vary from a small circle to a diagonal line. An easy way to find out the shape of this marking is to look at the pinout diagram on the data sheet of the device.

Figure 2-5 illustrates the small line that is usually located near pin 1 of the footprint. Use both package marking and footprint marking to match the location of pin 1 on the footprint to pin 1 on the device. If both the package marking and the footprint marking are located on top of each other, it is likely that the device was placed onto the PCB in the correct orientation.