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MSP430F5528 USB_DP question.

Luigi Evalle
Intellectual 815 points


Hi,

A bay area customer has inquired on the following:

"We followed the reference schematic for attaching BSL and came up with this: 

  [See attached image 1]

We have a circuit that drives the signal labeled USB_BSL high based on a button push.  

My question, is it OK for us to disconnect the USB_DP line from the circuit that drives PUR? 

Such as this: 


[See attached image 2]

 

Thanks for your help,

Luigi Evalle

  • 0
    Guru 34773 points

    Pulling USB_DP line is used for detection of device present on bus. Check Speed Identification chapter here http://www.beyondlogic.org/usbnutshell/usb2.shtml

    A USB device must indicate its speed by pulling either the D+ or D- line high to 3.3 volts. A full speed device, pictured below will use a pull up resistor attached to D+ to specify itself as a full speed device. These pull up resistors at the device end will also be used by the host or hub to detect the presence of a device connected to its port. Without a pull up resistor, USB assumes there is nothing connected to the bus. Some devices have this resistor built into its silicon, which can be turned on and off under firmware control, others require an external resistor.

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