Implementing a mass storage device, reading an external Image file

embedded_eng_ — Sun, 08 Aug 2021 15:13:07 GMT

Hi, I'm using lpcxpresso55s16_dev_composite_cdc_msc_bm with a LPC55S16-EVK board.

USB HS is connected to PC A and exposes a CDC interface and a HID interface, and USB FB is connected to PC B and exposes a MSC interface.

The general purpose is that PC B will be able to mount an img file that exist in PC A.

Every read request received from PC B is read by the MCU, then the MCU issues a HID command to PC A, asking the specific block, which is sent through a CDC channel.

Since the image size is 209715200 Bytes (409600 512 blocks), the capacityInformation->totalLbaNumberSupports parameter is set to be 409600.

usb_status_t USB_DeviceMscCallback(class_handle_t handle, uint32_t event, void *param) { usb_status_t error = kStatus_USB_Success; usb_device_lba_information_struct_t *lbaInformationStructure; usb_device_lba_app_struct_t *lbaData; usb_device_ufi_app_struct_t *ufi; usb_device_capacity_information_struct_t *capacityInformation; switch (event) { case kUSB_DeviceMscEventReadResponse: lbaData = (usb_device_lba_app_struct_t *)param; break; case kUSB_DeviceMscEventWriteResponse: lbaData = (usb_device_lba_app_struct_t *)param; break; case kUSB_DeviceMscEventWriteRequest: lbaData = (usb_device_lba_app_struct_t *)param; /*offset is the write start address get from write command, refer to class driver*/ lbaData->buffer = g_deviceComposite_fs->mscDisk.storageDisk + lbaData->offset * LENGTH_OF_EACH_LBA; break; case kUSB_DeviceMscEventReadRequest: lbaData = (usb_device_lba_app_struct_t *)param; /*offset is the read start address get from read command, refer to class driver*/ send_hid(lbaData->offset); //asks for the block in this offset lbaData->buffer = get_bulk();//get block from cdc break; case kUSB_DeviceMscEventGetLbaInformation: lbaInformationStructure = (usb_device_lba_information_struct_t *)param; lbaInformationStructure->logicalUnitNumberSupported = LOGICAL_UNIT_SUPPORTED; lbaInformationStructure->logicalUnitInformations[0].lengthOfEachLba = LENGTH_OF_EACH_LBA; lbaInformationStructure->logicalUnitInformations[0].totalLbaNumberSupports = 409600; lbaInformationStructure->logicalUnitInformations[0].bulkInBufferSize = 512; lbaInformationStructure->logicalUnitInformations[0].bulkOutBufferSize = 512; break; case kUSB_DeviceMscEventTestUnitReady: /*change the test unit ready command's sense data if need, be careful to modify*/ ufi = (usb_device_ufi_app_struct_t *)param; break; case kUSB_DeviceMscEventInquiry: ufi = (usb_device_ufi_app_struct_t *)param; ufi->size = sizeof(usb_device_inquiry_data_fromat_struct_t); ufi->buffer = (uint8_t *)&g_InquiryInfo; break; case kUSB_DeviceMscEventModeSense: ufi = (usb_device_ufi_app_struct_t *)param; ufi->size = sizeof(usb_device_mode_parameters_header_struct_t); ufi->buffer = (uint8_t *)&g_ModeParametersHeader; break; case kUSB_DeviceMscEventModeSelect: usb_echo("kUSB_DeviceMscEventModeSelect\r\n"); break; case kUSB_DeviceMscEventModeSelectResponse: ufi = (usb_device_ufi_app_struct_t *)param; break; case kUSB_DeviceMscEventFormatComplete: break; case kUSB_DeviceMscEventRemovalRequest: break; case kUSB_DeviceMscEventRequestSense: break; case kUSB_DeviceMscEventReadCapacity: capacityInformation = (usb_device_capacity_information_struct_t *)param; capacityInformation->lengthOfEachLba = LENGTH_OF_EACH_LBA; capacityInformation->totalLbaNumberSupports = 409600; break; case kUSB_DeviceMscEventReadFormatCapacity: capacityInformation = (usb_device_capacity_information_struct_t *)param; capacityInformation->lengthOfEachLba = LENGTH_OF_EACH_LBA; capacityInformation->totalLbaNumberSupports = 409600; break; default: break; } return error; }

I wrote a script for PC A that listens to the relevant /dev/hidraw port, and sends the blocks through the relevant /dev/ttyACM port.

Now, the only issue I have seems to be with the offsets.

When the USB FS is connected to PC B, after the following events:

kUSB_DeviceMscEventGetLbaInformation
kUSB_DeviceMscEventGetLbaInformation
kUSB_DeviceMscEventInquiry
kUSB_DeviceMscEventTestUnitReady
kUSB_DeviceMscEventReadCapacity
kUSB_DeviceMscEventModeSense
kUSB_DeviceMscEventModeSense
kUSB_DeviceMscEventTestUnitReady
kUSB_DeviceMscEventRemovalRequest
kUSB_DeviceMscEventTestUnitReady
kUSB_DeviceMscEventReadCapacity
kUSB_DeviceMscEventModeSense
kUSB_DeviceMscEventModeSense

4168 read events are received, with offsets:

0, 512, 1024, 1536, 2048, 2560, 3072, 3584

Then:

209649664, 209650176, 209650688, 209651200, 209651712, ,209652224 , 209652736...

Then:

0, 512, 1024, 1536, 2048, 2560, 3072, 3584..

It goes like this until 4168 request were made.

It asks for the same blocks several times.

After these events, a /dev/sdX1 partition appears on PC B.

Now, If I'm trying to mount the partition I get a filesystem error.

When I try to look at the content using hexdump command, PC B issues some more read commands, and I see: "This is not a bootable disk. please insert a bootable floopy and..."

Maybe someone can help with that?

Re: Implementing a mass storage device, reading an external Image file

embedded_eng_ — Tue, 10 Aug 2021 07:11:47 GMT

After some digging, seems that the problem is with the cdc that received the bulk data.

Since this have nothing to do with MSC, I will create a new post with the CDC issue.

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Implementing a mass storage device, reading an external Image file

Re: Implementing a mass storage device, reading an external Image file