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- =============================
- ISO7816 Serial Communications
- =============================
- 1. Introduction
- ===============
- ISO/IEC7816 is a series of standards specifying integrated circuit cards (ICC)
- also known as smart cards.
- 2. Hardware-related considerations
- ==================================
- Some CPUs/UARTs (e.g., Microchip AT91) contain a built-in mode capable of
- handling communication with a smart card.
- For these microcontrollers, the Linux driver should be made capable of
- working in both modes, and proper ioctls (see later) should be made
- available at user-level to allow switching from one mode to the other, and
- vice versa.
- 3. Data Structures Already Available in the Kernel
- ==================================================
- The Linux kernel provides the serial_iso7816 structure (see [1]) to handle
- ISO7816 communications. This data structure is used to set and configure
- ISO7816 parameters in ioctls.
- Any driver for devices capable of working both as RS232 and ISO7816 should
- implement the iso7816_config callback in the uart_port structure. The
- serial_core calls iso7816_config to do the device specific part in response
- to TIOCGISO7816 and TIOCSISO7816 ioctls (see below). The iso7816_config
- callback receives a pointer to struct serial_iso7816.
- 4. Usage from user-level
- ========================
- From user-level, ISO7816 configuration can be get/set using the previous
- ioctls. For instance, to set ISO7816 you can use the following code::
- #include <linux/serial.h>
- /* Include definition for ISO7816 ioctls: TIOCSISO7816 and TIOCGISO7816 */
- #include <sys/ioctl.h>
- /* Open your specific device (e.g., /dev/mydevice): */
- int fd = open ("/dev/mydevice", O_RDWR);
- if (fd < 0) {
- /* Error handling. See errno. */
- }
- struct serial_iso7816 iso7816conf;
- /* Reserved fields as to be zeroed */
- memset(&iso7816conf, 0, sizeof(iso7816conf));
- /* Enable ISO7816 mode: */
- iso7816conf.flags |= SER_ISO7816_ENABLED;
- /* Select the protocol: */
- /* T=0 */
- iso7816conf.flags |= SER_ISO7816_T(0);
- /* or T=1 */
- iso7816conf.flags |= SER_ISO7816_T(1);
- /* Set the guard time: */
- iso7816conf.tg = 2;
- /* Set the clock frequency*/
- iso7816conf.clk = 3571200;
- /* Set transmission factors: */
- iso7816conf.sc_fi = 372;
- iso7816conf.sc_di = 1;
- if (ioctl(fd_usart, TIOCSISO7816, &iso7816conf) < 0) {
- /* Error handling. See errno. */
- }
- /* Use read() and write() syscalls here... */
- /* Close the device when finished: */
- if (close (fd) < 0) {
- /* Error handling. See errno. */
- }
- 5. References
- =============
- [1] include/uapi/linux/serial.h
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