stm32f3 'USER USB' not detected

Question

I'm working on stm32f3 discovery board. For my current project I planned on coding a simple UART program on the board, I happened to read somewhere on the internet that to use the board for UART communication with PC the 'USER USB' has to be used.

My questions are the following

Firstly when i connect my board to PC using the 'USER USB'. The PC refuses to recognize the board.(F.Y.I- OS used is windows 7 64bit). This problem persists even after I update the driver! How to resolve this?
Is the "Connecting USER USB" part correct? because I can't see any RS232 chip on board
Should I use an add on board?

P.S I've installed all the necessary drivers from ST website and works flawlessly while using 'ST-Link interface' part of the board

Where do you get information about "USER USB"? may be they think that you need your own UART to USB converter. — vlk

timoist timoist · Accepted Answer · 2017-08-08T17:37:12

Thanks for the post, had the same issue, here is what I added Approach: Turn-off USB lines programmatically by changing input to output, forcing it to zero and reenable them after around 1 second Also used power-off and on from ST USB Libs

// Force Re-Enumeration by the USB Host
//
int     aux_retrigger_usb()
{
        GPIO_InitTypeDef  GPIO_InitStructure;

        // ST USB Function
        PowerOff();

        // Program Pin 12 USB_DP from Input to Output
        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12;

        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
        GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
        GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

        GPIO_Init(GPIOA, &GPIO_InitStructure);
        // Set USB_DP to 0

        GPIOA->BRR  |= GPIO_Pin_12 ;

        // Wait for for minimum 32* 50msec ,  1,6 secs
        while(tim3_cnt%32!=0) ; while(tim3_cnt%32!=31) ;

        // ST USB Functions
        PowerOn();
        USB_Init();
        Virtual_Com_Port_Reset() ;

        // Program Pin 12 USB_DP from Output to input

        GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_12;
        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
        GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
        GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
        GPIO_Init(GPIOA, &GPIO_InitStructure);

        return 1 ;
}

So basically to avoid the power on race condition, the ports may be programmed first to outputs and then released after 1 second.

stm32f3 'USER USB' not detected

2 Answers