Exploring the DELL D/Bay USB Port
 

Why you can't use an external D/Bay CDRW on a standard USB port

I was tempted to use a spare external drive and cut off the connector, only to realize that even with the idea of supplying the extra power to the drive, the USB signals are NOT enough to make it work.

This is because the main board expects to FIRSTLY communicate with the peripheral NOT through the USB port, but through the SMBus (SMB_DAT & SMB_CLK).

The data transfer then occurs through the USB lines (for speed)

By the way, power is supplied onto PWR_SRC only after the device has been recognized and enabled.

EXTERNAL

INSIDE - INTERNAL INTERFACE

CABLE

POWER

DATA

 

3 pin 12V PWR SRC

7 pin

 

  • PWR.SRC

  • PWR_GND

 

  • VCC

  • D-

  • D+

  • GND

  • SMBDAT

  • SMBCLK

  • MODPRES#


INTERNAL INTERFACE (Save in full resolution)

Dell D/Bay CDRW Internal Interface PD01S

7 pin connector JUSB1 and 3 pin connector JUSB2

 

Pin at plug

Inline pins
 (internal)

Signal

 

Pin

Inline Pins
 (internal)

Signal

1

1

USB_VCC

 

8

6

SMB_CLK

2

2

USB_D-

 

9

GND

PWR_GND

3

3

USB_D+

 

10

 

SHIELD GND

4

4

USB_GND

 

11

 

SHIELD GND

5

+ 12

PWR_SRC

 

12

 

SHIELD GND

6

5

SMB_DAT

 

13

 

SHIELD GND

7

7

MODPRES#

 

14

 

SHIELD GND