The first section of this document describes how to use the PN532 RFID NFC module with Raspberry Pi. In the second section the basic steps required for preparing a Mifare Ultralight card for storing NDEF records are provided.

This section briefly covers the setup of the PN532 RFID NFC module with Raspberry Pi. The module is connected to the Raspberry Pi via I2C and controlled via libnfc.

⚠️ In case the used PN532 module offers multiple interfaces ensure that it is configured (check for jumpers/switches) for I2C.

Connect the I2C pins to the following physical pins on the Raspberry Pi.

• GND -> 6
• VCC -> 4
• SDA -> 3
• SCL -> 5

Note on Raspberry Pi pin numbering:

---------------------------
| 2 4 6 8                 | Header
| 1 3 5 7 ...             |
---------------------------
|                         | Remaining board
|                         |
|     Raspberry Pi        |
|                         |
|--------------------------

Use the Raspberry Pi configuration tool called raspi-config to enable the I2C interface.

sudo raspi-config nonint do_i2c 0

Optional, check if the PN532 module is available on the I2C bus. Use i2cdetect from the i2c-tools package to scan the I2C bus for devices.

sudo apt update
sudo apt install i2c-tools

i2cdetect -y 1 #scan bus 1 for devices

Example output (device found at addr 24)

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- 24 -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

In case the module ist not found use i2cdetect -l to list available I2C buses and scan them for devices by changing the bus number passed to i2cdetect(see man page).

Install latest version of libnfc from repo.

sudo apt update
sudo apt install libnfc6 libnfc-bin libnfc-examples

Add config for the PN532 module to libnfc (assumes that module is connected to bus 1, if not change /dev/i2c-1 accordingly).

sudo mkdir -p /etc/nfc/devices.d
printf 'name = "pn532"\nconnstring = "pn532_i2c:/dev/i2c-1"\n' | sudo tee /etc/nfc/devices.d/pn532.conf

Poll NFC tag to check if libnfc is fuctional.

nfc-poll

This section briefly outlines the steps required to prepare a blank Mifare Ultralight card as a NFC Forum Type 2 Tag for storing NDEF records and shows how to store a URL in a NDEF record.

Blank Mifare Ultralight cards ship with an empty one time programmable (OTP) area located in block/page 3. The NFC Forum Type 2 Tag Operation Specification puts the Capability Container (CC) used for managing information on the tag at this block. To initialize the card the CC must be written.

⚠️ You only have one shot - As the name suggest the OTP can only be written once. Therefore, extrem care should be taken when writting the CC. Otherwise you may end up with a broken card.

One easy way to manually add the CC is to modify the dump of a blank Mifare Ultralight card. For this the card is first dumped with nfc-mfultralight.

nfc-mfultralight r blank.mfd

Subsequently, the dump editable is converted into a hexdump with xxd in order to make it editable with a standard texteditor.

xxd -c 4 blank.mfd > blank.hex

A dump of an empty card is shown below, the OTP area is located in row XXX.