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USB CDC connection (plug / unplug cable)

Ricardo Crudo

Hello.

I am having a issue with USB CDC (running in a LPC1788). If I power up a mother board with the USB cable (NXP device) already connected, the O.S. (Linux) does not identify the device, but if I unplug and plug it again it is identified and works fine. The same thing happens if I reset my NXP board, the O.S. does not identify the NXP device until that I unplug/plug the cable.

I checked the code, and what happen is that the application stays forever in the while (!USB_Configuration); loop.
Is necessary some configuration on USB device to that the device do an auto-configuration when it is already plugged?

Regards,
Ricardo

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    UM10470
    Chapter 12: LPC178x/7x USB device controller

    12.6.7 SoftConnect
    The connection to the USB is accomplished by bringing D+ (for a full-speed device) HIGH
    through a 1.5 kOhm pull-up resistor. The SoftConnect feature can be used to allow
    software to finish its initialization sequence before deciding to establish connection to the
    USB. Re-initialization of the USB bus connection can also be performed without having to
    unplug the cable.
    To use the SoftConnect feature, the CONNECT signal should control an external switch
    that connects the 1.5 kOhm resistor between D+ and +3.3V. Software can then control the
    CONNECT signal by writing to the CON bit using the SIE Set Device Status command.

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  • 0

    UM10470
    Chapter 12: LPC178x/7x USB device controller

    12.6.7 SoftConnect
    The connection to the USB is accomplished by bringing D+ (for a full-speed device) HIGH
    through a 1.5 kOhm pull-up resistor. The SoftConnect feature can be used to allow
    software to finish its initialization sequence before deciding to establish connection to the
    USB. Re-initialization of the USB bus connection can also be performed without having to
    unplug the cable.
    To use the SoftConnect feature, the CONNECT signal should control an external switch
    that connects the 1.5 kOhm resistor between D+ and +3.3V. Software can then control the
    CONNECT signal by writing to the CON bit using the SIE Set Device Status command.

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