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
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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
