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mma8452 reading the device with interrupts configured

Question asked by chinmay nanda on Aug 5, 2013
Latest reply on Aug 12, 2013 by Tomas Vaverka


   I am using MMA8452 in one of the projects I am working on and am facing some problem when trying to read the device configuring the interrupts. The interrupt line stays active low/ active high on the device so my interrupt never vectors to the ISR thread.

1. I am doing the following configuration setting on the device



    i2c_RegWrite(CTRL_REG1, tx_para[0]& ~(ACTIVE_MASK));



    i2c_RegWrite(CTRL_REG1, DATA_RATE_1250US);

    i2c_RegWrite(XYZ_DATA_CFG_REG, FULL_SCALE_8G);

    i2c_RegWrite(CTRL_REG3, 0);

    i2c_RegWrite(CTRL_REG4, INT_EN_DRDY);

    i2c_RegWrite(CTRL_REG5, INT_CFG_DRDY); // send on pin1




    i2c_RegWrite(CTRL_REG1, tx_para[0]& (ACTIVE_MASK));


    q.num_bytes = ARRAY_SIZE;

    if (ioctl(fd, CONFIG_DEVICE, &q) == -1)


        perror("query_apps ioctl set\n");


    printf("configured values :\n");

    i2c_RegRead(CTRL_REG1, 1,&tx_para[0]);

    printf("value at address:0x%2X is  0x%X\n",CTRL_REG1,tx_para[0]);

    i2c_RegRead(XYZ_DATA_CFG_REG, 1,&tx_para[0]);

    printf("value at address:0x%2X is  0x%X\n",XYZ_DATA_CFG_REG,tx_para[0]);

    i2c_RegRead(CTRL_REG3, 1,&tx_para[0]);

    printf("value at address:0x%2X is  0x%X\n",CTRL_REG3,tx_para[0]);

    i2c_RegRead(CTRL_REG4, 1,&tx_para[0]);

    printf("value at address:0x%2X is  0x%X\n",CTRL_REG4,tx_para[0]);

    i2c_RegRead(CTRL_REG5, 1,&tx_para[0]); // send on pin1

    printf("value at address:0x%2X is  0x%X\n",CTRL_REG5,tx_para[0]);

// read the xyz data registers to assert the interrupt the same is assertedlater on in the module. so I expect to fire the interrupt from this point onwards

    q.buff[0] = 0x01;

    q.num_bytes = 6; //< 10 !!


   // unsigned int i = 0 ;


    if (ioctl(fd, MMA8452_IOC_READ_NBYTES, &q) == -1)


        perror("query_apps ioctl get");




        for(i = 0 ; i < q.num_bytes ; i ++)


            printf("Read Data %d\n", q.buff[i]);




the IOCTL module is my own cosutom module , I can read from and write to the device using the same so I am confident that the module is otherwise functional.

I am configuring the interrupts on line INTR1 and reading the data registers first time after that I am reading the status and the data registers in interrupt in the module as follows:



irq_handler_t thread_fn(void)


    //struct timespec t;

    time_t curr_time ;   // get time now

    struct tm * now ;

    printk(KERN_ERR "in_intr...\n");

    char status,reg;

    //struct Accel_data Axis_dat_thread0[SINGLE_DATA_SET_K],Axis_dat_thread1[SINGLE_DATA_SET_K];

    //static isr_thread,current_set = 0;


// NEED TO READ THE intr source bit as well

    reg = 0x0C;


    if( status & 0x01)


         reg = MMA8452_REG_DATA;

         if ( mma8452_i2c_rx_data(reg,6,&raw_axis_data[0]) < 0 ) // change


            return -EFAULT;



the interrupt is configured as follows

status = request_threaded_irq (irq_num,NULL,(irq_handler_t)thread_fn,IRQF_TRIGGER_FALLING|IRQF_ONESHOT,"MMA8452_intr1",NULL);


Can some one kindly guide me what could be going wrong ? I am not putting the process to sleep anywhere.