Is there a low cost and reliable way to identify a USB charging port?
I plan to charge a device via the USB port. The USB Battery Charging Specification 1.1 allows 1.5A current draw when connected to a Dedicated Charging Port (DCP) and 500mA when connected to a Charging Downstream Port (CDP). A DCP is typically a wall wart and a CDP is typically a computer. As far as I understand, a DCP is identified by shorted D+ and D-lines, a CDP id identified by D+ and D- being pulled to ground through 15k resistors.
It seems like identifying these ports takes quite a bit of extra hardware. I could probably bias the D+ line and connect D- to an ADC input to look for a DCP. And some similar arrangement to check for a CDP. I assume I would also need to disconnect the bias and ADC when done to not interfere with USB communication. The USB pads on my mcu are not 5V tolerant and are dedicated USB pads (I'm using an LPC1343).
Identifying the non-standard Apple and Sony chargers would be an added bonus, but not critical.
Does anyone see a simpler or better way to do this?
From this datasheet