STM32F4 USB HID Change PID (Product ID) during runtime

Posted on September 15, 2014 at 16:08

Hi

I do not know why you want to change the Product ID, changing it may cause miss match in device type (HID) and therefore driver

However :

''generate 'something' in the STM32F4 USB Stack to force the PC to reconnect the USB device?''

        // force a USB soft disconnect

        // USB_OTG_dev.regs.DREGS->DCTL |= 0x02;

Setting and clearing the 0x02 bit will make the PC think the device has been unplugged/plugged in the USB

Posted on September 16, 2014 at 13:26

Hi Mr Cat ;).

many thanks for the quick reply. 

USB_OTG_dev.regs.DREGS->DCTL |= 0x02;

Delay(100ms);

USB_OTG_dev.regs.DREGS->DCTL &= ~0x02;

with some time delay inbetween works perfect.

I have one Hardware where up to 2 can be connected at the same time to the PC.

To distinguish both I need 2 USB handles, which I retrieve from the PID.

The PID itself can be changed via USB and will be stored in a flash page of the processor. The processor itself needs to continue working, therefore a MCU reset is not possible, and to request the user to re-plugin the USB cable is inconvenient. Therefore I need this kind of device re-connect on the PC side.

If you know an other option I'm open for that, as I have not jet so much experience with USB (just getting started vew months ago).

cheers

Posted on September 16, 2014 at 13:52

Hi

''I have one Hardware where up to 2 can be connected at the same time to the PC.

To distinguish both I need 2 USB handles, which I retrieve from the PID.''

That is a PC Host issue and should not affect the STM32 target.

For example, if you have 2/3/4/5 identical USB mice (mouse) and you plug them all in.

Do you expect every mouse to change their PID just because there is another one?

How does each mouse know another one has been plugged in?

The PID of the STM32 target should not change.

It is up to the PC (Host) to enumerate each identical USB device with a different 'handle'

This handle is different to the PID. Again, think of the mouse example I gave.

I am not a PC programmer, so I lack the expertise.

The PID is used to identify the USB device type and help load the driver.

If you change the PID, the PC Host will try to load a new driver

Posted on September 16, 2014 at 18:46

> I have one Hardware where up to 2 can be connected at the same time to the PC.

> To distinguish both I need 2 USB handles, which I retrieve from the PID. Usually, the same model of devices share the same PID. Unique serial number on each device identifies the target device. The serial number on the libraries, \STM32_USB-Host-Device_Lib_V2.1.0\Project\USB_Device_Examples\HID\src\usbd_desc.c #define USBD_SERIALNUMBER_HS_STRING ''00000000011B'' #define USBD_SERIALNUMBER_FS_STRING ''00000000011C'' STM32Cube_FW_F4_V1.3.0 Unique serial number is generated for each chip, using Device IDs on the chip Refer to void Get_SerialNum(void) (usbd_desc.c) Windows application retrieves serial number using HidD_GetSerialNumberString() To pick up all of attached HID devices of the same VID/PID,

Jan Axelson’s generic_hid_vb_50
FrmMain.vb
Private Function FindTheHid() As Boolean
...
Do
...
If (MyHid.DeviceAttributes.VendorID = myVendorID) And _
(MyHid.DeviceAttributes.ProductID = myProductID) Then
...
myDeviceDetected = True ' <- here, don’t set this value to True
' And then, this loop picks up all of
' HID device of specified VID/PID
...
Loop Until (myDeviceDetected Or (memberIndex = devicePathName.Length))

Tsuneo