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Ux_Device_CCID application description

This application provides an example of Azure RTOS USBX stack usage on STM32G474E-EVAL board, it shows how to develop USB Device for Integrated Circuit Card Interface Device based application.

The application is designed to emulate a smart card reader device, the code provides all required device descriptors framework and associated Class descriptor to build a USB CCID device.

At the beginning ThreadX call the entry function tx_application_define(), at this stage, all USBx resources are initialized, the CCID Class driver is registered and the application creates 2 threads with the same priorities :

  • usbx_app_thread_entry (Prio : 10; PreemptionPrio : 10) used to initialize USB HAL PCD driver and start the device.
  • usbx_ccid_thread_entry (Prio : 20; PreemptionPrio : 20) used to simulate Card insert remove detection.

CCID reader example is hosted on PC and can be tested with any PC/SC application using contactless interface smart card. The PC/SC interface is a specification for contact and contactless smartcard into the computer eco-system. When device is plugged with the USB link, the CCID device is controlled using this interface through several commands APDUs.

The smart card receives an ISO7816-4 compliant APDU within a CCID device. With respect to PC/SC specification the reader interprets this APDU. Each command APDU sent has an associated ending response.

Command APDU: CLA INS P1 P2 Lc Data Le Response APDU: Data SW1 SW2

Expected success behavior

When plugged to PC host, the STM32G474E-EVAL must be properly enumerated as an USB CCID device. During the enumeration phase, device provides host with the requested descriptors (Device, configuration, string). Those descriptors are used by host driver to identify the device capabilities. Once the STM32G474E-EVAL USB device successfully completed the enumeration phase, send and receive the CCID class commands through the bulk out, bulk in and interrupt endpoints:

  • CCID Events like card detection or removal are sent on the Interrupt Endpoint.
  • CCID Commands are sent on BULK-OUT Endpoint.
  • CCID Responses are sent on BULK-IN Endpoint.

To start using pssc tool such as Cryptware Smart Card Console, Smart card ToolSet Pro or SpringCard PC/SC Diag, follow next steps:

  • Connect the board to the PC with the USB cable.
  • Open the PC/SC application tool, the card gets detected and the ATR appears.
  • Enter the following commands one by one in the command APDU area and check the response.

APDU Supported:

  • ENABLE CHV1: A0 28 00 01 08 CHV1 value - success Message 90 00 is displayed.
  • SELECT: A0 A4 00 00 02 File ID - success Message 90 00 is displayed.
  • VERIFY: A0 20 00 xx 08 CHV Value - success Message 90 00 is displayed.
  • CHANGE: A0 24 00 xx 10 Old CHV, New CHV - success Message 90 00 is displayed.
  • GET RESPONSE: A0 C0 00 00 - success Message 90 00 is displayed and the written data is displayed
  • READ BINARY: A0 B0 xx xx - success Message 90 00 is displayed and the read data is displayed.

For warning processing, execution error or the unsupported command: message 69 99 - 63 C0 - 88 88 is displayed.

Error behaviors

Host PC shows that USB device does not operate as designed (CCID Device enumeration failed, no card reader detected in PS/SC tool).

Assumptions if any

User is familiar with USB 2.0 "Universal Serial BUS" Specification and CCID class Specification.

Known limitations

None .

ThreadX usage hints

  • ThreadX uses the Systick as time base, thus it is mandatory that the HAL uses a separate time base through the TIM IPs.

  • ThreadX is configured with 100 ticks/sec by default, this should be taken into account when using delays or timeouts at application. It is always possible to reconfigure it in the "tx_user.h", the "TX_TIMER_TICKS_PER_SECOND" define,but this should be reflected in "tx_initialize_low_level.S" file too.

  • ThreadX is disabling all interrupts during kernel start-up to avoid any unexpected behavior, therefore all system related calls (HAL, BSP) should be done either at the beginning of the application or inside the thread entry functions.

  • ThreadX offers the "tx_application_define()" function, that is automatically called by the tx_kernel_enter() API. It is highly recommended to use it to create all applications ThreadX related resources (threads, semaphores, memory pools...) but it should not in any way contain a system API call (HAL or BSP).

  • Using dynamic memory allocation requires to apply some changes to the linker file. ThreadX needs to pass a pointer to the first free memory location in RAM to the tx_application_define() function, using the "first_unused_memory" argument. This require changes in the linker files to expose this memory location.

    • For EWARM add the following section into the .icf file:
    place in RAM_region    { last section FREE_MEM };
    • For MDK-ARM:
    either define the RW_IRAM1 region in the ".sct" file
or modify the line below in "tx_initialize_low_level.S to match the memory region being used
    LDR r1, =|Image$$RW_IRAM1$$ZI$$Limit|
    • For STM32CubeIDE add the following section into the .ld file:
    ._threadx_heap :
  {
     . = ALIGN(8);
     __RAM_segment_used_end__ = .;
     . = . + 64K;
     . = ALIGN(8);
   } >RAM_D1 AT> RAM_D1

    The simplest way to provide memory for ThreadX is to define a new section, see ._threadx_heap above.
In the example above the ThreadX heap size is set to 64KBytes.
The ._threadx_heap must be located between the .bss and the ._user_heap_stack sections in the linker script.
Caution: Make sure that ThreadX does not need more than the provided heap memory (64KBytes in this example).
Read more in STM32CubeIDE User Guide, chapter: "Linker script".
    • The "tx_initialize_low_level.S" should be also modified to enable the "USE_DYNAMIC_MEMORY_ALLOCATION" flag.

USBX usage hints

None .

Keywords

RTOS, ThreadX, USBXDevice, USB, Full Speed, CCID, ICC

Hardware and Software environment

  • This example runs on STM32G4xx devices.
  • This example has been tested with STMicroelectronics STM32G474E-EVAL boards Revision MB1397 Revision B-05 and can be easily tailored to any other supported device and development board.

How to use it ?

In order to make the program work, you must do the following :

  • Open your preferred toolchain
  • Rebuild all files and load your image into target memory
  • Run the application