Posted on April 11, 2016 at 17:08I'm currently having some issues with the USB core on the STM32f4. Before enabling the USB core the VBUS line (GPIO A9) is low as would be expected. when a usb cable is plugged it I detect this and enable my USB core using the following function:
void MX_USB_Init(void)
{
if(USBState == Disabled){
/* Init Device Library */
USBD_Init(&USBD_Device, &VCP_Desc, 0);
/* Add Supported Class */
USBD_RegisterClass(&USBD_Device, USBD_CDC_CLASS);
/* Add CDC Interface Class */
USBD_CDC_RegisterInterface(&USBD_Device, &USBD_CDC_fops);
/* Start Device Process */
USBD_Start(&USBD_Device);
USBState = Enabled;
}
}
This works fine and the USB appears to communicate correctly with the PC, the problem comes however when I disconnect the USB cable. Originally I wasn't deinitializing the USB core, but it was noticed that if the core was active, VBUS would output 1.9V. I then wrote the following function to disable the USB core
void MX_USB_Deinit(void)
{
if(USBState == Enabled){
/* Stop Device Process */
USBD_Stop(&USBD_Device);
/* Deinit Device Library */
USBD_DeInit(&USBD_Device);
USBState = Disabled;
}
}
However I'm not sure it has fully shut down the USB core as I still have a voltage on USB VBUS (GPIO A9).
