Can two USBs, both in mass storage mode, work simultanoeusly?

[messer79]

Hello,

My cutom device, powered by STM32F429ZI, has two USB ports. Each one is connected via USBLC6-2 (ESD protection) chip to MCU (USB FS and USB HS) pins. VBUS is not used.

I use CubeMX (the latest version) to generate initial code.

If I configure FS (PA11, PA12 pins) port as a mass storage device (host only) AND leave HS disabled I am able to initialize USB stick and explore files from MCU via FATFS. So this works great.

If I configure HS (PA14, PB15 pins) port as mass storage device (host only) AND leave FS disabled I am, again, able to initialize USB stick and explore files from MCU via FATFS. So this also works OK.

IF I configure FS port as mass storage device (host only) and HS port as a communication device (device only) I am in a position to explore files from MCU and send messages to my computer (they show up in a terminal). This also works if I swap ports functions (make FS a CDC and HS a MSC). So, again, it is OK.

Now the issue occurs:

If I configure both - FS & HS as mass storage devices (host only) then the only one USB stick is initialized (and can be accessed vis FATFS). The second USB stick remains in HOST_IDLE status all the time. I tried swapping sticks and changing USBH instances. Nothing helps.

That's why I am curious if it is possible to run 2 USB ports in mass storage mode. If yes, I am asking you to answer me what I am missing. You could ask me why I needed this configuration. The answer is simple - just a proof of concept. I am just mastering STM32.

Thank you in advance for any answers or hints.

[Tesla DeLorean]

I would expect the hardware to be capable, I would suspect a failure at the abstraction/object level. With HAL and CubeMX it is a matter of how deep down the rabbit hole to want to go to fix issues and test things.

[Pavel A.]

IIRC the Cube has a small bug when both USB controllers have same host class and you need to fix the generated code manually.

Probably still persists in the current version.

-- pa

[messer79]

Thank you for the answer. Are you in a position to tell me where exactly the bug is and maybe you know how to fix it?

[Pavel A.]

In one project created long ago with old version of Cube, it was in the function MX_USB_HOST_Init.

It can be named differently in the current version.

Look for assignment of classes to the USB host controllers, like this:

USBH_Init(&hUsbHostHS, USBH_UserProcess, HOST_HS);
USBH_RegisterClass(&hUsbHostHS, USBH_HID_CLASS);
USBH_Start(&hUsbHostHS);
.....
USBH_Init(&hUsbHostFS, USBH_UserProcess, HOST_FS);
USBH_RegisterClass(&hUsbHostFS, USBH_HID_CLASS);
USBH_Start(&hUsbHostFS);

The catch is that USBH_HID_CLASS is actually pointer to a global struct so both instances share it. But it has some writable data that should be private to each instance.

So I've changed it to:

static USBH_ClassTypeDef hidClass2;
...
memcpy(&hidClass2, USBH_HID_CLASS, sizeof(hidClass2));
 
USBH_Init(&hUsbHostHS, USBH_UserProcess, HOST_HS);
USBH_RegisterClass(&hUsbHostHS, USBH_HID_CLASS);
USBH_Start(&hUsbHostHS);
 
USBH_Init(&hUsbHostFS, USBH_UserProcess, HOST_FS);
USBH_RegisterClass(&hUsbHostFS, &hidClass2);
USBH_Start(&hUsbHostFS);

A horrible quick hack, but worked at least for the HID class...

-- pa