STM32F072xx USB Hardware

[jezell]

Posted on June 14, 2016 at 22:54

Hello,

Where can I find info on hardware needed to run USB to my STM32F072CB?  I found the reference design and read hardware getting started.  Neither specify how to get USB levels down from 5V to uC VDD.  5V can't go directly into VDDIO2 since max recommended value is +3.6V.  Do I just have to add hardware convert logic signals back and forth between VDD and 5V?  This seems inefficient.In the reference design schematic USB_VDD seemingly comes from no where.  It just appears but it's not connected to any power supply or regulator in the schematic.  Help to point me in the right direction is greatly appreciated.

[Tesla DeLorean]

Posted on June 14, 2016 at 23:03

DP/DM don't need level conversion. They are not signalling at 5V

You will likely need to take the 5V from the USB connector, and have a 3V3 regulator to power the STM32If you're going to talk about schematics, et al, please provide a cite so I don't have to search for the same documentation you are referring too.

[Walid FTITI_O]

Posted on June 15, 2016 at 11:45

Hi jamieB,

I recommend that you get inspired from the design shematic of STM32F0 board. As a reference, take a look at p 38 of the STM32F0Discovery board's User manual

http://www.st.com/content/ccc/resource/technical/document/user_manual/30/ae/6e/54/d3/b6/46/17/DM00050135.pdf/files/DM00050135.pdf/jcr:content/translations/en.DM00050135.pdf

. -Hannibal-

[jezell]

Posted on June 15, 2016 at 20:01

Apologies for not citing the reference schematic.

I used the 

32F072BDISCOVERY

schematic as reference.  In this schematic VDD_USB is connected to VDDIO2 but VDD_USB comes from no where I can find.  Link to schematic below:

 

http://www.st.com/resource/en/schematic_pack/stm32f072b-disco_sch.zip

[Tesla DeLorean]

Posted on June 15, 2016 at 21:21

The USB_VDD net is bonded to the VDD net via SB16 (Solder Bridge, pg 3)

The VDD net is bonded to the 3V net via the JP2 (IDD Jumper, pg 2), ie where you could measure current consumption of the STM32F0 in-circuitThe  VDD_USB (VDDIO2)  net is also exposed on the P2 Header. ie you could break the solder bridge and supply your own voltage, while powering the core at a lower voltage. The VDD_USB requires a sufficiently high voltage so the pin drivers meet USB specs, but the core can function at levels far below that.