Hello,
I am developing a USB HID application on STM32L443. The HID communication works in both directions when I put the controller in Sleep mode with WFI and Sleep on Exit. I am currently experimenting on the suspend/resume capability of the USB. I have 2 LED on my board and I toggle them in the USB interrupt routine on suspend and resume events. On a Linux host machine I am using the powertop utility to manually send suspend and wake-up signals. I assume this setup works, because the LEDs flash the way they should when I send the suspend/wake-up commands. According to the datasheet, the USB peripheral is able to wake up the MCU from Stop0/1 modes. So I try the following in the USB interrupt routine:
if (USB->ISTR & USB_ISTR_SUSP)
{
USB->ISTR = USB_CLR_SUSP;
USB->CNTR |= USB_CNTR_FSUSP;
USB->CNTR |= USB_CNTR_LPMODE;
if(device_status == USB_CONFIGURED)
{
SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
}
}
if (USB->ISTR & USB_ISTR_WKUP)
{
USB->ISTR = USB_CLR_WKUP;
USB->CNTR &= ~USB_CNTR_LPMODE;
RCC->AHB2ENR |= RCC_AHB2ENR_GPIOCEN;
GPIOC->ODR ^= GPIO_ODR_OD14;
SCB->SCR &= ~SCB_SCR_SLEEPDEEP_Msk;
USB->CNTR &= ~USB_CNTR_FSUSP;
}
I am using HSE with PLLs for SystemClock and USB clock. I have set up HSI16 as a wake up clock in RCC->CFGR. EXTI line 17 (USB FS) is enabled by default, according to the reference manual. The device does enter Stop0 after sending suspend command with powertop - the current consumption drops from 3mA in Sleep mode to around 350uA. I expect that when I send a resume signal, the MCU will power on the HSI16 and deal with the USB interrupt, where as you can see, I simply start the GPIO clock (the pin is configured as an output before the USB initialization) and toggle the LED, I am not restarting the HSE and the USB yet. And it does not work. If I do not enter Stop0 after a suspend signal, the wake-up signal is recognized and the LED lights up. Does anyone know how to correctly wake up a STM32 from stop mode with USB?
