bbb_eeprom.c

/*
 * bbb_eeprom.c  Read Model & SerialNo from BeagleBone Black's EEPROM via i2c
 *
 * Compile with:
 *     cc bbb_eeprom.c -o bbb_eeprom
 *
 * Winston Smith <smith.winston.101@gmail.com>
 *
 * History:
 *   2014-05-01  Initial Implementation for FreeBSD
 *   2014-05-17  Port to Linux
 */

#include <stdint.h>
#include <sys/cdefs.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <unistd.h>

#if defined(__linux__)
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#else
#include <dev/iicbus/iic.h>
#endif

#if defined(__linux__)
#define I2CRDWR I2C_RDWR
#define IIC_M_RD I2C_M_RD
#define IIC_M_WR 0
#define iic_rdwr_data i2c_rdwr_ioctl_data
#define iic_msg i2c_msg
#define slave addr
#endif

/*
 * Read data from an i2c device
 */
int i2c_read(int fd, int slave, uint8_t* buffer, uint16_t offset, uint16_t len)
{
    struct iic_msg msg[2];
    struct iic_rdwr_data rdwr;


    msg[0].slave = slave;
    msg[0].flags = IIC_M_WR;
    msg[0].len = sizeof(offset);
    msg[0].buf = (uint8_t*)&offset;

    msg[1].slave = slave;
    msg[1].flags = IIC_M_RD;
    msg[1].len = len;
    msg[1].buf = buffer;


    rdwr.nmsgs = 2;
    rdwr.msgs = msg;

    if (ioctl(fd, I2CRDWR, &rdwr) < 0) {
        return errno;
    }

    return 0;
}

/*
 * BeagleBone Black system EEPROM signature
 */
uint8_t signature[] = { 0xAA, 0x55, 0x33, 0xEE };

int main(int argc, char **argv)
{
    int     fd;
#if defined(__linux__)
    char*   dev = "/dev/i2c-0";
#else
    char*   dev = "/dev/iic0";
#endif
    int     addr = 0x50;
    uint8_t buffer[28];
    char    work[32];
    int     err;


    if (argc > 1) {
        dev = argv[1];
    }

    if ((fd = open(dev, O_RDWR)) < 0 )  {
        perror("open failed");
        exit(-1);
    }

    // For sanity checking!
    memset((void*)buffer, '@', sizeof(buffer));

    if ((err = i2c_read(fd, addr, buffer, 0, sizeof(buffer))) != 0) {
        printf("i2c_read() failed with: %s (%d)\n", strerror(err), err);
        exit(1);
    }

    close(fd);

    printf("Read from slave %02X on %s: signature=%02X:%02X:%02X:%02X\n",
           addr,
           dev,
           buffer[0], buffer[1], buffer[2], buffer[3]);

    if (memcmp((void*)buffer, (void*)signature, sizeof(signature)) != 0) {
        printf("ERROR: EEPROM signature mismatched\n");
        exit(1);
    }

    // Extract the 12 bytes allocated to the model
    strncpy(work, (char*)&buffer[4], 12);
    work[12] = 0;
    printf("Model:\t%s\n", work);

    // Extract the 12 bytes allocated to the serial number
    strncpy(work, (char*)&buffer[16], 12);
    work[12] = 0;
    printf("Serial:\t%s\n", work);


    exit(0);
}