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5222x/5225x USB host mode pulldown confusion...

Question asked by Rich Testardi on Jul 4, 2009
Latest reply on Jul 6, 2009 by Rich Testardi

Hi all,

 

I'm trying with no luck to convince myself of the USB OTG pullup and pulldown functionality in the 5222x/5225x.

 

I've used the same SIE in other MCUs where the pullup and pulldown resistors controlled by:


  // enable usb pull downs  MCF_USB_OTG_OTG_CTRL =    MCF_USB_OTG_OTG_CTRL_DM_LOW|MCF_USB_OTG_OTG_CTRL_DP_LOW|      MCF_USB_OTG_OTG_CTRL_OTG_EN;

 

are actually internal to the MCU...

 

However, I see on the M52259DEMOKIT and M52223EVB, external resistors tied to different pins, as follows:

 

  M52259DEMOKIT

    pulldowns tied to qspi_cs2 (USB_DM_PDOWN) and qspi_cs3 (USB_DP_PDOWN)

    pullup tied to irq1* (USB_ALTCLK)

 

  M52223EVB

    pulldowns tied to qspi_cs2 (USB_DM_PDOWN) and qspi_cs3 (USB_DP_PDOWN)

    pullup tied to qspi_cs1 (USB_PULLUP)

 

On the M52259DEMOKIT, the pullup circuitry is installed despite a "do not install" listing on the schematic.

 

Now, on the M52221DEMO board, on the other hand, none of this kind of circuitry exists.  And in fact, on the 64 pin parts, the qspi_cs1, qspi_cs2, and qspi_cs3 pins don't even exist.

 

So, I guess I'm looking for confirmation that no internal pull resistors exist on these parts, or correction that they do...  Is that even true for the device mode pullup?

 

And then I'm wondering if you simply can't use the USB OTG with pullup/pulldown switching on a 64 pin part?  And if using irq1* instead of qspi_cs1 is legitimate on the 52259 (on which qspi_cs1 doesn't exist)?  And if I can just use any other GPIO's as well (and in particular, if the pullup in the GPIO when configured as input to act "turned off" will bite me)?  Is there a way to get more "open drain"'ish than simply configuring a GPIO as input?

 

Thanks for any insight or confirmation!!!

 

-- Rich

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