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Electronics => Beginners => Topic started by: Curby on January 08, 2018, 08:52:15 pm

Title: STM32 USB together with USBLC6
Post by: Curby on January 08, 2018, 08:52:15 pm

Hello,

I have a question about the USB of an STM32 device. The Controller I want to use is the STM32F413VGT6.

I don't want to use the 5V provided by the USB host and I only want to run it as a USB device using a USB B Connector.

Are the following steps correct?

• I connect GND of the Connector with GND of my Board.
• I connect the Shield of the Connector with (1M || 4.5nF) to GND of my Board.
• I connect D- and D+ the following way: Dx -> USBLC6 -> 22ohm -> STM32
• The VUSB from the Connector is only connected with the USBLC6 VBUS input

My µC is running at 3.3V. Will there be any problems with the 5V USB data lines?

Thank your for any advices!

Title: Re: STM32 USB together with USBLC6
Post by: Signal32 on January 08, 2018, 10:25:09 pm

1 & 3 are the correct approach.
Not sure about 2 & 4.
But there will be no issue with the 3.3V / 5V voltage mismatch. USB is actually 3.3V or lower, the 5V is there only to provide power to devices on the bus, with no relation to the actual USB protocol itself.

Title: Re: STM32 USB together with USBLC6
Post by: mbless on January 09, 2018, 01:41:00 am

Take a look at the Nucleo data sheet (http://www.st.com/content/ccc/resource/technical/document/user_manual/group0/26/49/90/2e/33/0d/4a/da/DM00244518/files/DM00244518.pdf/jcr:content/translations/en.DM00244518.pdf) for this processor. Figure 18 shows how the usb is connected. USB 5v is tied to PA9,  USB_FS_USB, with a 10k resistor.