MDK MIDDLEWARE: Set Inquiry Data of a Logical Unit During Runtime

Information in this knowledgebase article applies to:

• MDK v5.x
• MDK Middleware USB Component v6.x

QUESTION

I am developing a USB Device Mass Storage Class (MSC) application. I'd like to use the same binary image in production. How do I reconfigure the inquiry data of a logical unit during runtime?

ANSWER

In the configuration file "USBD_Config_MSC_#.h", find the following code:

//This is the default for USB Device MSC #0 logical unit
#define USBD_MSC0_LUN1_INQUIRY_DATA     "Keil    "         \ 
                                        "Disk LUN 1      " \ 
                                        "1.0 "

Replace the above section with the following code:

#include <stdint.h>
extern uint8_t msc0_runtime_inquiry_string[];
#define USBD_MSC0_LUN1_INQUIRY_DATA    msc0_runtime_inquiry_string

Then in a source file, define the default string and the new inquiry string:

  uint8_t msc0_runtime_inquiry_string[28] =
   "Vendor  "            /* Vendor Information:      8 bytes */ \ 
   "Product         "    /* Product Identification: 16 bytes */ \ 
   "Rev "                /* Product Revision Level:  4 bytes */ \ 
;


  uint8_t msc0_runtime_inquiry_string_new[28] =
   "Vendor B"            /* Vendor Information:      8 bytes */ \ 
   "Product       2"    /* Product Identification: 16 bytes */ \ 
   "Rev2"                /* Product Revision Level:  4 bytes */ \ 
;

Then in the application, a simple copy can update the inquiry string:

  #include "rl_usb.h"
  #include <string.h>
  extern uint8_t msc0_runtime_inquiry_string[];
  extern uint8_t msc0_runtime_inquiry_string_new[];
//...
  memcpy( msc0_runtime_inquiry_string, msc0_runtime_inquiry_string_new, 28);
//...
  USBD_Initialize         (0);          /* USB Device 0 Initialization        */
  USBD_Connect            (0);          /* USB Device 0 Connect               */
//...

to use the new inquiry string inside the USB Device. The memcpy() can be called before or after the USB layer is initialized.

For a unique label in the inquiry string, many Cortex-M devices already have a unique device ID that would be an ideal addition.

Note: In this example, the application stores the strings in RAM. If the new string is dynamically generated during runtime (in a one-time event) then a robust application should store the new inquiry string in an area of non-volatile memory to protect the data from a power cycle. The filesystem integrated with the USB MSC layer could backup the new string, as long as it is not a RAM-based filesystem. The presence of an earlier startup string would also have to be acceptable.

MORE INFORMATION

• Refer to USB MSC Configuration

Last Reviewed: Friday, January 8, 2021