Virtual COM Port: UART over USB for STM32F072

[gaurav2]

Posted on June 04, 2016 at 00:28

Dear all,

I am trying to get UART (USART?) working over USB for a STM32F072C8 part. The idea is to get basic getc/putc working via the USB for a custom board that we have designed. I intend to make the device  look like CDC class to the Windows Host PC so that I can use a Putty or Hyper-term to just get the output (UART Tx from STM32) on a console terminal.

I looked at the sample code in STM32CubeF0 for USB_Device/CDC_Standalone for the STM32F072B_Eval project. Obviously this is for the Discovery or similar boards while our board is custom and different set of peripherals are used.

In any case, I had hoped to pull out the essential components but the USB device is not recognized by the host PC.  The Win Device Manager has an error/warning triangle mark.

Question - what are the things that I should look at and how do I proceed with the debug? The example seems to use 48MHz clock called USE_USB_CLKSOURCE_CRSHSI48 in the main.h file. However, we have a 12 MHz crystal on our board.

Can somebody tell me where all and what all do I have to change from the STM32CubeF0 Project for _Eval to get it going with 12MHz?

Many thanks!

[Tesla DeLorean]

Posted on June 04, 2016 at 00:51

The HSI is an internal clock, your external 12 MHz will only come into play if you enable it, and the PLL to generate an alternate 48 MHz clock.

[gaurav2]

Posted on June 04, 2016 at 01:12

Thanks Clive. That makes sense then. I should expect to get the COM port working with the HSI (high speed internal) oscillator of 48MHz itself.

Any further ideas why I might be getting ''error code 10 - this device cannot start?'' message in the Device Manager?

[slimen]

Posted on June 06, 2016 at 10:26

Hi,

About''error code 10 - this device cannot start?'', it can be related to theHS max packet size.

You can refer to this

https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/STM32F429%20USB%20error%20code%2010&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=37

tomore understand about this issue.

Regards