How to sleep when USB_VBUS on stm32f105 is low?

[CDew.1]

I have a self-powered device.  It appears as a USB CDC device /dev/ttyACM0, when plugged into a Linux host.  The device port is wired to USB_VBUS, so that pin will only be high when connected to a USB host.

I would like to detect the presence of the USB cable, so that the device can sleep if there is no cable and other conditions are met.

- How can I detect the presence of the USB cable?  I'm using CubeIDE and the HAL.

- How can I put the STM32 to sleep in such a way that it will wake up when the USB cable is plugged back in?

[FBL]

Hi @CDew.1 

If your device is self-powered, you can configure a GPIO pin to detect the VBUS level. 

Generally, to wake up a FS device from a suspend state, the host needs to drive low D+ to the K-State. Check section 28.5.2 Peripheral states in Reference Manual

[CDew.1]

Thanks for your reply.  My self-powered device is always USB device and never a host.

I currently have PA9 configured as USB_OTG_FS_VBUS.

- Will USB (device) continue to work if I change PA9 to a GPIO_Input?

- Or do I need to rework the board to route VBUS to an *additional* GPIO pin?

(I was hoping that there was a HAL_ function which I could poll to see if USB_OTG_FS_VBUS was high.)

[CDew.1 · Accepted solution]

I've found a solution:

int usb_plugged_in = HAL_GPIO_ReadPin(PMU_LED_PWR_GPIO_Port, PMU_LED_PWR_Pin / 2);

where PMU_LED_PWR is the name of PA10.  PA9 is on the same port as PA10 and its pin mask is right-shifted.

i.e. Setting PA9 to the role of USB_OTG_FS_VBUS makes it a GPIO input at a lower level, but doesn't give you a name to reference it.  By calculating USB_OTG_FS_VBUS's port struct and pin mask, you can access it.

[CDew.1]

More neatly:

#define USB_OTG_FS_VBUS_GPIO_Port PMU_LED_PWR_GPIO_Port

#define USB_OTG_FS_VBUS_Pin (PMU_LED_PWR_Pin >> 1)

int usb_plugged_in = HAL_GPIO_ReadPin(USB_OTG_FS_VBUS_GPIO_Port, USB_OTG_FS_VBUS_Pin);

where PMU_LED_PWR is the name of PA10.