USB CDC Communications for Dummies!

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  1. - 1st January 2009, 02:24 #11
    Darrel Taylor's Avatar
    Darrel Taylor
    Darrel Taylor is offline Fanatical Contributor
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    If it compiles ... The number one cause of USB failure, is improper Oscillator Configurations.

    For 4Mhz Crystal ...
    Code:
    @   __CONFIG   _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@   __CONFIG   _CONFIG1H, _FOSC_HSPLL_HS_1H
    For 8Mhz Crystal ...
    Code:
    @   __CONFIG   _CONFIG1L, _PLLDIV_2_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@   __CONFIG   _CONFIG1H, _FOSC_HSPLL_HS_1H
    For 20Mhz Crystal ...
    Code:
    @   __CONFIG   _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@   __CONFIG   _CONFIG1H, _FOSC_HSPLL_HS_1H
    For any of the above configurations, use ...
    Code:
    DEFINE OSC 48
    Number two reason ... improper capacitance on VUSB pin. (0.22uF or higher)

    #3, connecting +5V from USB port to +5V supply from powered project. (very bad)
    Ok, that's not really #3, but it is bad.

    Last edited by Darrel Taylor; - 1st January 2009 at 02:47. Reason: OSC 48
    DT
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