STM32L4 DISCO USB DEVICE DOES NOT WORK

Posted on April 11, 2016 at 14:23

Hi zhang.gang.001,

Thank you for your feedback. The issue has been reported internally.

-Syrine-

Posted on April 11, 2016 at 15:09

Dear Syrine,

i made some more experiments on this behavior: if i only use usb (the uart is initialized) it worked fine, send/receive both directions are tested with a terminal program, no problem. but if i tried to send something via uart1, i got a suspend interrupt from the usb controller

(__HAL_PCD_GET_FLAG(hpcd, USB_OTG_GINTSTS_USBSUSP), it then closed the connection and tried to reopen it (i thing after the uart1 trasmitt completion), but it failed. the transmitt via uart1 was ok.

Posted on April 11, 2016 at 21:27

Hi zhang and Syrine,

Current version of CubeMX generates very dangerous code for USB devices on 32L476G DISCO board. You may burn out the OTG_FS_VBUS (PC11) pin, by output conflict, if you would run generated code without any fix.

STM32CubeMX: v4.0

STM32Cube_FW_L4_V1.4.0

Target: 32L476G DISCO board - all of USB device class

Problem around VBUS pin

1) MX_GPIO_Init() in main.c sets up OTG_FS_VBUS (PC11) pin as output, low-level.

2) STMPS2141 (VBUS switch chip for host) sources 5V to this pin. MX_GPIO_Init() enables (active-low) this chip.

3) Also, when you plug-in your board to PC USB port, 5V comes from host.

And then, PC11 drops these 5V sources into GND.

Here is fix for this problem.

main.c

void MX_GPIO_Init(void)

{

// line 399

/*Configure GPIO pins : OTG_FS_PowerSwitchOn_Pin OTG_FS_VBUS_Pin */

//GPIO_InitStruct.Pin = OTG_FS_PowerSwitchOn_Pin|OTG_FS_VBUS_Pin; // <--- (**)

GPIO_InitStruct.Pin = OTG_FS_PowerSwitchOn_Pin;

// line 415

/*Configure GPIO pin Output Level */

//HAL_GPIO_WritePin(GPIOC, OTG_FS_PowerSwitchOn_Pin|OTG_FS_VBUS_Pin, GPIO_PIN_RESET); // <--- (**)

HAL_GPIO_WritePin(GPIOC, OTG_FS_PowerSwitchOn_Pin, GPIO_PIN_SET);

Replace above (**) lines with next lines

This fix does,

- OTG_FS_VBUS is left in default (floating)

- Diable STMPS2141 chip

> If i also initialize teh UART1, USB works

It's because, UART1 TX shares VBUS (PA9) pin with OTG_FS.

Modify this line to USBD_LL_Init() in usbd_conf.c, so that OTG_FS ignores VBUS level.

usbd_conf.c

USBD_StatusTypeDef USBD_LL_Init (USBD_HandleTypeDef *pdev)

{

// line 321

// hpcd_USB_OTG_FS.Init.vbus_sensing_enable = ENABLE;

hpcd_USB_OTG_FS.Init.vbus_sensing_enable = DISABLE;

> I used a 32khz on LSE and PLL.

Unfortunately, current CubeMX doesn't enable LSE-PLL for MSI

You have to enable it manually, inserting this code to SystemClock_Config() on main.c

main.c

void SystemClock_Config(void)

{

...

/* Enable MSI Auto-calibration through LSE */

HAL_RCCEx_EnableMSIPLLMode();

CubeMX setting for CDC and fixed sources (main.c and usbd_conf.c) are attached to this post.

Tsuneo

________________

Attachments :

cube_l476_disco_cdc_dev.zip : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I0d1&d=%2Fa%2F0X0000000bcJ%2FylCEHotWLxrnk1jbxqBIlHf6aMA80rJCnNYdJd4rArg&asPdf=false

Posted on April 12, 2016 at 09:48

Hi chinzei.tsuneo,

You are right, for DISCO board one has to turn OTG_FS_PowerSwitchOn(PC9) as output hight AND OTG_FS_VBUS(PC11) as input with pulldown (or high z if unused).

recently i used the Arduino board for testing and there is no such problem.

As you mentioned the line

hpcd_USB_OTG_FS.Init.vbus_sensing_enable = ENABLE;

is wrong.

I didn't get Suspend interrupt any more after i disabled vbus sensing in code.

Now I'll try to remove uart1 initialization and see if usb device works along

thanks.