As you can see from the above image, the power and ground pins of a USB connector are situated on its either side and the two data pins are placed in between. Also notice that the data pins are situated a bit inward compared to the power pins. As a result of this, when you plug in a USB, power is supplied to the device first before it can begin transferring data.
“Okay, that’s fine, but what am I to do with this?” you ask.
Well, my friend, you can exploit this subtle feature by plugging a USB port only half way into the device. This enables the device to power up without making a data connection. In case of a mobile phone, you can connect the data cable half way to charge the phone without mounting the SD card. This can be pretty useful when working with MP3 players too.
“This is pretty cool!” you say. “Thanks!”