Posted on June 06, 2015 at 06:24Hello,
I'm curious if you resolved this issue? I am debugging the same problem on an stm32L0.
I used stmCube to create a DFU image which I have flashed and the device does appear in DFU mode.
dfu-util -l outputs the following:
Found DFU: [0483:df11] ver=0200, devnum=35, cfg=1, intf=0, alt=0, name=''UNKNOWN'', serial=''00000000001A''
However, when I try to actually flash I get the same message:
dfu-util: Could not read name, sscanf returned 0
I've tracked down why this is happening and why the string is ''UNKNOWN'' but I'm trying to understand why it is happenning.
If I do lsb -v I get this info(trimmed)
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 254 Application Specific Interface
bInterfaceSubClass 1 Device Firmware Update
bInterfaceProtocol 2
iInterface 6
The key here is the last line, 'iInterface 6'. I have read this is supposed to be the index of the interface name.
dfu-util calls the libusb function to get the name:
if (intf->iInterface != 0)
ret = libusb_get_string_descriptor_ascii(devh,
intf->iInterface, (void *)alt_name, MAX_DESC_STR_LEN);
where intf->iInterface is 6.
This ends up running the following function in the stm32 firmware:
static void USBD_GetDescriptor(USBD_HandleTypeDef *pdev ,
USBD_SetupReqTypedef *req)
<snip>
case USB_DESC_TYPE_STRING:
switch ((uint8_t)(req->wValue))
{
case USBD_IDX_INTERFACE_STR:
pbuf = pdev->pDesc->GetInterfaceStrDescriptor(pdev->dev_speed, &len);
break;
default:
#if (USBD_SUPPORT_USER_STRING == 1)
pbuf = pdev->pClass->GetUsrStrDescriptor(pdev, (req->wValue) , &len);
break;
#else
USBD_CtlError(pdev , req);
return;
#endif
static void USBD_GetDescriptor(USBD_HandleTypeDef *pdev ,
USBD_SetupReqTypedef *req)
So for me, the lower byte of req->wValue is 6 but the value ofUSBD_IDX_INTERFACE_STR is 0x5. So the incoming request for theinterace name always gets an error and thus dfu-util fails.
Also it look like dfu-util expects the name in a specific format for dfuse devices:
ret = sscanf(intf_desc, ''@%[^/]%n'', name, &scanned);
if (ret < 1) {
free(name);
warnx(''Could not read name, sscanf returned %d'', ret);
return NULL;
}
And the name generated by Cube doesn't match that format:
#define USBD_INTERFACE_STRING_FS ''DFU Interface''
So I've got a couple more things to dig into but wanted to see if you found anything while debugging this issue.
thanks,
jeff
