Run the SL030 RFID reader on linux

I needed to use the SL030 RFID reader on linux (on a beaglebone with i2c support enabled, of course). But when I tried to communicate with the device using i2cget, the device failed and disappeared from the detected devices… After the break, we’ll see why and how I solved it.

My first contact with the SL030 has been using arduino, using the SL018 library and everything worked really fine.

So given the really low price of the product, it has been quite obvious to me that I would use again the [SL030](http://www.stronglink-rfid.com/en/rfid-modules/sl030.html|en] for another beaglebone based project.

So, I plugged the SL030 in the matching /dev/i2c-3 device, which is wired per default on the beaglebone. Then I ran :

% i2cdetect -r -y 3
    0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: 50 -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         

and found my device is lying on the address 50. And then, I tried to get a full dump of the device using i2cdump, and that not only did not work (only XX values for every register), but when I ran again i2cdetect the device disappeared !

So, I read the documentation thoroughly and found out that the SL030 is not a register-based i2c device, but it is using a command scheme :

write:
[ADDRESS|REGISTER|LENGTH|COMMAND|DATA]

read:
[ADDRESS|REGISTER|LENGTH|COMMAND|STATUS|DATA]

So I made a little C code that reads a tag when one is present:

// under WTFPL license

#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>


const char STATUS[][32] = {
    /*0x00*/ "Operation succeed",
    /*0x01*/ "No tag",
    /*0x02*/ "Login succeed",
    /*0x03*/ "Login fail",
    /*0x04*/ "Read fail",
    /*0x05*/ "Write fail",
    /*0x06*/ "Unable to read after write",
    /*0x08*/ "Address overflow",
    /*0x09*/ "Download Key fail",
    /*0x0A*/ "Collision occur",
    /*0x0C*/ "Load key fail",
    /*0x0D*/ "Not authenticate",
    /*0x0E*/ "Not a value block"
};

int main(void) {
    int file;
    char filename[40];
    const char *buffer;
    int addr = 0x50; // Addr of SL030

    sprintf(filename,"/dev/i2c-3");
    if ((file = open(filename,O_RDWR)) < 0) {
        printf("Failed to open the bus.");
        exit(1);
    }

    if (ioctl(file,I2C_SLAVE,addr) < 0) {
        printf("Failed to acquire bus access and/or talk to slave.\n");
        exit(1);
    }
    char buf[128] = {0};
    for (int i=0;i<128;++i) buf[i] = 0;

    // ------------ WRITE COMMAND ------------------
    unsigned char reg = 0x01; // Device register to access
    buf[0] = 1;
    buf[1] = reg;

    if (write(file,buf,2) != 2) {
        // ERROR HANDLING: i2c transaction failed
        printf("Failed to write to the i2c bus.\n");
        buffer = strerror(errno);
        printf(buffer);
        printf("\n\n");
    } else {
        printf("write success\n\n");
    }

    for (int i=0;i<128;++i) buf[i] = 0;

    struct timespec tim, tim2;
    tim.tv_sec = 0;
    tim.tv_nsec = 20000000;
    nanosleep(&tim,&tim2);

    // ------------ READ CARD STATUS ------------------
    unsigned short len=0;
    unsigned short cmd=0;
    unsigned short sta=0;
    // Using I2C Read
    if (read(file,buf,128) <= 0) {
        // ERROR HANDLING: i2c transaction failed
        printf("Failed to read from the i2c bus.\n");
        buffer = strerror(errno);
        printf(buffer);
        printf("\n\n");
        return 1;
    }
    len = (unsigned short)buf[0];
    cmd = (unsigned short)buf[1];
    sta = (unsigned short)buf[2];

    printf("Length:  %d\n",len);
    printf("Command: 0x%02X\n",cmd);
    printf("Status:  %s\n",STATUS[sta]);
    printf("Data: ");
    for (int i=3;i<len;++i)
        printf("%02X;", buf[i]);

    printf("\n\n");

    return 0;
}

use it, share it, improve it !

this code is actually based on this one.

this code can be downloaded as a gist as well

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