USB 2.0 D+ PullUp requiered?

[benjaminbrammer9]

Posted on March 18, 2017 at 17:13

Hi Guys,

I want to implement the STM32F303VET6 for possible DFU or CDC / HID . I am a little bit mixed up with the schematics of the USB ST-LINK for USB interfacing. Is the 1,5k PullUp on D+ mandatory? And if it is, do i need to implement the possibility to activate or deactivate it? the schematics from the ST-LINK use a GPIO for that purpose but where in the middlewre software do I need to implement that PullUp switching?

When I use the STM32CubeMX software and want to activate the USB only both differential lines are set but no aditional GPIO port for the PullUp. On the other hand the datasheet recommends to use the PullUp since it is requested in the USB 2.0 spec. So if the PullUp is a must, why is there no true description on how to implement that PullUp right in software and layout?

best regards

Benjamin

#implementation #1.5k-pull-up #usb #stm32

[benjaminbrammer9]

Posted on March 20, 2017 at 11:09

This would not be necessary. The device shall only be connected for DFU or a prior configuration. After that there is no need to be attached to a USB host and it's not intended. What I still don't get, if there is a need to implement an additional USB PHY chip, or is this all implemented in the STM32 interface? The block diagram is not clear about that, in my opinion.

best regards

Benjamin

[benjaminbrammer9]

Posted on March 20, 2017 at 11:18

But I think there is no need for an additional USB PHY, because only the differential lines are supported by the STM32F303xx so the PHY seems to be part of the interface, though the block diagram looks as if there is a need for a seperate transceiver.