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

[S.Ma]

Posted on March 18, 2017 at 18:06

Newer STM32 Usb ips seem to intergrate the pull up to simplify the design. Check schematics and reference manuals.

[benjaminbrammer9]

Posted on March 19, 2017 at 12:49

Hello, thanks for the advise, but I cannot switch anymore because I am far to deep in the realization of the project

[Rob.Riggs]

Posted on March 19, 2017 at 04:35

It's been a while since I did an STM32F303-based board.  It did require that I supply the 1.5K pull-up on D+.  I solved that issue by using an STF202-22T1G IC which has an integrated pull-up and the 22R termination resistors which you will also need.

I recommend switching the the L4 parts if you can.  They have a much improved USB interface and are more power efficient.

[S.Ma]

Posted on March 19, 2017 at 06:45

Agreed, USB device without crystal or USB Host from 32768Hz external crystal through MSI are additional upgrades.