Testing RFID Reader on Pi

In order to ensure communication between the SainSmart RFID-RC522 module is occurring correctly with the Raspberry Pi, I have developed a short routine that reads the version information from the controller on the module.

initialization of the RP

Need to initialise the connection between the Raspberry Pi and the RFID module. The connection for which is shown in early blog rfid-and-raspberry-pi. This sets the speed of the SPI interface and configures the GPIO interface to allow a hardware reset to be sent to the module.

Code snippet

def __init__(self,spd=1000000):     spi.openSPI(speed=spd)     GPIO.setmode(GPIO.BOARD)    # Set the mode of numbering the pins.     GPIO.setup(self.NRSTPD, GPIO.OUT)    # GPIO pin 22 is the output (NRSTPD - Reset)     GPIO.output(self.NRSTPD, 1) # Set GPIO pin 22 to high (set low to reset)

Reading the version setting

To access data on the module a read or write operation needs to be performed on the appropriate register, this requires sending the command via the spi.transfer command to the attached module.

For finding the version we need to read the register in the module that relates to the version. From the documentation for the NXP RC522 chip the register is known as VersionReg

  VersionReg      = 0x37 # shows the software version

The format of the command is given below.

msb = 1 for read / 0 for write

6 bits for register address

lsb = 0

To correctly format the data to be sent for the NXP RC522, we need to do the following

1. bit shift the register address left by one bit
2. ensure the lsb is zero
3. set the msb to 1 for a read / 0 for a write

This can be done by using the following

(((MIFAREReader.VersionReg<<1) & 0x7E ) | 0x80,0)

The read operation returns a two byte value, the first indicating a successful operation, the second indicates the version which can be decoded.

The complete code for this is shown below

Code snippet

readerVersion = spi.transfer((((MIFAREReader.VersionReg<<1) & 0x7E ) | 0x80,0)) if readerVersion[1] == 0x91: print "Reader Version: MFRC522 1.0 software version" if readerVersion[1] == 0x92: print "Reader Version: MFRC522 2.0 software version"

To read the software version from the module we just need to put the code together. A screenshot of the resulting output is shown below.

Sourcecode

I am developing a SourceForge site to host code from this project. At the moment it is only in the very initial stages of setting the site up.

Download of the code described is available here

http://sourceforge.net/projects/rasprfid/files/ReaderV.py/download

Over the coming months I will be publishing more on hacking RFID using the Raspberry Pi.