How can I use USB (CDC) without the VBus connection on the STM32H755?

[JE2]

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I am trying to use USB(CDC) without  the VBus connection on the STM32H755(Nuclueo-H755ZI-Q).

But I can't.

Please tell me the correct confinglation and procedure

I use ST USB middleware with CDC class.

There is no sample project for STM32H755.

So I ported myself.

It worked.(with VBus)

I changed following points for using without VBus.

comment out following.(main() "main.c")

HAL_PWREx_EnableUSBVoltageDetector();

comment out followings.(void HAL_PCD_MspInit(PCD_HandleTypeDef * hpcd) "usbd_conf.c")

/* Configure VBUS Pin */
GPIO_InitStruct.Pin = GPIO_PIN_9;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

And I checked this.

USBD_StatusTypeDef USBD_LL_Init(USBD_HandleTypeDef * pdev) "usbd_conf.c"

hpcd.Init.vbus_sensing_enable = 0;

                                                    ~~~

* this value was already "0".

At first, it seemed to work,

But that was wrong.

After running code with VBus enabled, if you debug-execute code with VBus disabled in CubeIDE without powering off, it works. However, it fails to run after powering off.

I have experience running USB without VBus on STM32L4 and STM32F4.

On those models, simply setting

hpcd.Init.vbus_sensing_enable = 0;

 made it work.

I think STH32H755 requires other procedure.

Does anyone know about this?

I already saw https://community.st.com/t5/stm32-mcus-products/stm32h7-usb-cdc-without-vbus-pin/td-p/754880

So I believe this is possible.

[Gyessine · Accepted solution]

Hello, @JE2 
Can you specify whether the USB device is bus-powered or self-powered? and if self-powered , can you provide the GPIO pin that you are using?

Because based on AN4879section 2.6
a USB device must use VBUS sensing detection. There are two cases:

• Bus-powered USB device: VBUS sensing is not mandatory because USB is always connected when the device is powered.
• Self-powered USB device: VBUS sensing is mandatory.

However, I tried replicating your case on my end, and I did not encounter any problems. I am attaching the project in case it can help you.

Gyessine

[JE2]

Thank you Gyessine!

It worked!

I ported just a following point from "H755_CDC.zip".

In usbd.conf

My original code(This is STM32Cube's code(STM32Cube_FW_H7_V1.11.0) as is, unchanged.)

/**
  * @brief  Suspend callback.
  * @PAram  hpcd: PCD handle
  * @retval None
  */
void HAL_PCD_SuspendCallback(PCD_HandleTypeDef * hpcd)
{
  USBD_LL_Suspend(hpcd->pData);
}

Gyessine's solution

void HAL_PCD_SuspendCallback(PCD_HandleTypeDef * hpcd)
{
  USBD_LL_Suspend(hpcd->pData);
  __HAL_PCD_GATE_PHYCLOCK(hpcd);
  /* Enter in STOP mode. */
  /* USER CODE BEGIN 2 */
  if (hpcd->Init.low_power_enable)
  {
    /* Set SLEEPDEEP bit and SleepOnExit of Cortex System Control Register. */
    SCB->SCR |= (uint32_t)((uint32_t)(SCB_SCR_SLEEPDEEP_Msk | SCB_SCR_SLEEPONEXIT_Msk));
  }
  /

Thanks!

[JE2]

I didn't answer the Gyessine's question.

I'm developing a self-powered device.

The pins used for USB are:

• PA11 USB DM
• PA12 USB DP

You wrote this configuration requires VBus sensing.

Now I'm using Nuclueo-H755ZI-Q. This board has its VBus pin(PA9) physically connected.

I will check again when I get our prototyped board.