@FiiO
I have a Fiio_test app in my X5 3rd gen. When I fire up the app and plug in my device into a USB port, it can detect two states:
USB_SDP and USB_CDP
USB_SDP detects the device, I'm able to mount the drives. USB_CDP doesn't. This is on the same laptop with two different USB ports.
So from my understanding, the only reason why the device would not mount drives on a computer is if that computer's ports are not powered the same way. Any input on that on your part?
Thanks!
**edit** Info on SDP vs CDP:
Standard Downstream Port (SDP) refers to a port on a host or hub that’s compliant with USB 2.0 specifications. This means a SDP port can provide different power, depending upon the state of connection with the USB device. An SDP port expects a downstream device to have the following maximum current consumption in different states:
- 2.5mA when the device is in a suspended state
- 100mA when connected and not configured
- 500mA or the amount of current requested by the device’s configuration descriptor, whichever is less, when configured
When a USB device is connected to a SDP, the device can draw 100mA and up to 500mA once the device is enumerated successfully by the host. The charging setup as described for the personal computer example of the previous section represents a Standard Downstream Port.
Charging Downstream Port (CDP) refers to a port on a host or hub that’s compliant with USB 2.0 specifications. But unlike the SDP, a CDP port allows a USB device to draw more current, thereby facilitating faster charging. When a portable device is connected to a charging port, it is expected to behave in the following way:
- 2.5mA when the device is in a suspended state
- 100mA when it is connected and not configuUSred
- Maximum of 1.5A when configured
Source:
http://www.embedded.com/design/powe...ttery-charging-protocols-Android-based-design
**edit** So the site upgrade removed part of my post...
Charging downstream port (CDP) BC1.1 defines this new, higher current USB port for PCs, laptops, and other hardware. Now the CDP can supply up to 1.5A, which is a departure from USB 2.0 because this current can be supplied before enumeration. A device plugged into a CDP can recognize it as such by means of a hardware handshake implemented by manipulating and monitoring the D+ and D- lines. (See USB
Battery Charging Specification, section 3.2.3.) The hardware test takes place before turning the data lines over to the USB transceiver, thus allowing a CDP to be detected (and charging to begin) before enumeration.
Here's more information on CDP. So a hardware handshake failure between Fiio X5 and USB port??