path: root/Documentation/nfc/nfc-pn544.txt
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authorAnton Arapov <>2012-04-16 10:05:28 +0200
committerAnton Arapov <>2012-04-16 10:05:28 +0200
commitb4b6116a13633898cf868f2f103c96a90c4c20f8 (patch)
tree93d1b7e2cfcdf473d8d4ff3ad141fa864f8491f6 /Documentation/nfc/nfc-pn544.txt
parentedd4be777c953e5faafc80d091d3084b4343f5d3 (diff)
fedora kernel: d9aad82f3319f3cfd1aebc01234254ef0c37ad84v3.3.2-1
Signed-off-by: Anton Arapov <>
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+Kernel driver for the NXP Semiconductors PN544 Near Field
+Communication chip
+Author: Jari Vanhala
+Contact: Matti Aaltonen (matti.j.aaltonen at
+The PN544 is an integrated transmission module for contactless
+communication. The driver goes under drives/nfc/ and is compiled as a
+module named "pn544". It registers a misc device and creates a device
+file named "/dev/pn544".
+Host Interfaces: I2C, SPI and HSU, this driver supports currently only I2C.
+The Interface
+The driver offers a sysfs interface for a hardware test and an IOCTL
+interface for selecting between two operating modes. There are read,
+write and poll functions for transferring messages. The two operating
+modes are the normal (HCI) mode and the firmware update mode.
+PN544 is controlled by sending messages from the userspace to the
+chip. The main function of the driver is just to pass those messages
+without caring about the message content.
+In the normal (HCI) mode and in the firmware update mode read and
+write functions behave a bit differently because the message formats
+or the protocols are different.
+In the normal (HCI) mode the protocol used is derived from the ETSI
+HCI specification. The firmware is updated using a specific protocol,
+which is different from HCI.
+HCI messages consist of an eight bit header and the message body. The
+header contains the message length. Maximum size for an HCI message is
+33. In HCI mode sent messages are tested for a correct
+checksum. Firmware update messages have the length in the second (MSB)
+and third (LSB) bytes of the message. The maximum FW message length is
+1024 bytes.
+For the ETSI HCI specification see
+The Hardware Test
+The idea of the test is that it can performed by reading from the
+corresponding sysfs file. The test is implemented in the board file
+and it should test that PN544 can be put into the firmware update
+mode. If the test is not implemented the sysfs file does not get
+> cat /sys/module/pn544/drivers/i2c\:pn544/3-002b/nfc_test
+Normal Operation
+PN544 is powered up when the device file is opened, otherwise it's
+turned off. Only one instance can use the device at a time.
+Userspace applications control PN544 with HCI messages. The hardware
+sends an interrupt when data is available for reading. Data is
+physically read when the read function is called by a userspace
+application. Poll() checks the read interrupt state. Configuration and
+self testing are also done from the userspace using read and write.
+Example platform data:
+static int rx71_pn544_nfc_request_resources(struct i2c_client *client)
+ /* Get and setup the HW resources for the device */
+static void rx71_pn544_nfc_free_resources(void)
+ /* Release the HW resources */
+static void rx71_pn544_nfc_enable(int fw)
+ /* Turn the device on */
+static int rx71_pn544_nfc_test(void)
+ /*
+ * Put the device into the FW update mode
+ * and then back to the normal mode.
+ * Check the behavior and return one on success,
+ * zero on failure.
+ */
+static void rx71_pn544_nfc_disable(void)
+ /* turn the power off */
+static struct pn544_nfc_platform_data rx71_nfc_data = {
+ .request_resources = rx71_pn544_nfc_request_resources,
+ .free_resources = rx71_pn544_nfc_free_resources,
+ .enable = rx71_pn544_nfc_enable,
+ .test = rx71_pn544_nfc_test,
+ .disable = rx71_pn544_nfc_disable,