Odd behaviour with F_STATUS register FXOS8700C

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Odd behaviour with F_STATUS register FXOS8700C

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kaslewis
Contributor III

Hello,

When using the FXOS in FIFO mode the FIFO is read out when a watermark interrupt is set. The issue that I am seeing is the register indicates a watermark interrupt 0x54 but after reading the first three samples (0x01 - 0x06) the auto increment goes back to 0x00 and this time the F_STATUS reads 0xFF other values seen in the same read are 0x08, 0x0D as well as others.

screenshot.pngUnless I am misreading the data something seems wrong here, The F_STATUS register is not reading anything intelligible after its first read and the data from the XYZ axis should be 0g, 0g and 1g but instead I am seeing:

X - 0x0000, 0xF8FF...

Y - 0xFFBC, 0xE40F...

Z - 0x0FA0, 0xC400...

of which only the first value makes any sense any help with this issue would be very much appreciated.

Thanks

K

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TomasVaverka
NXP TechSupport
NXP TechSupport

Hello Kas,

See my answer in your another thread - FXOS8700 data appears very noisy

Regards,

Tomas

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TomasVaverka
NXP TechSupport
NXP TechSupport

Hello Kas,

Could you please post here your complete source code so I can review it and reproduce your settings?

Meanwhile, I would recommend you to take a look at our AN4073 including several code examples.

Regards,

Tomas

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kaslewis
Contributor III

Hello Tomas,

I am writing my code using mbed, I have included all my code below as requested.

Thankfully

Kas

#include "mbed.h"

#include "SDFileSystem.h"

//FXOS8700CQ

#define FXOS_ADDRESS_W              0x3C

#define FXOS_ADDRESS_R              0x3D

#define FXOS_STATUS                 0x00

#define FXOS_OUT_X_MSB              0x01

#define FXOS_F_SETUP                0x09

#define FXOS_TRIG_CFG               0x0A

#define FXOS_SYS_MOD                0x0B

#define FXOS_INT_SOURCE             0x0C

#define FXOS_WHO_AM_I               0x0D

#define FXOS_ID                     0xC7

#define FXOS_XYZ_DATA_CFG           0x0E

#define FXOS_TRANSIENT_CFG          0x1D

#define FXOS_TRANSIENT_SRC          0x1E

#define FXOS_ASLP_COUNT             0x29

#define FXOS_CTRL_REG_1             0x2A

#define FXOS_CTRL_REG_2             0x2B

#define FXOS_CTRL_REG_3             0x2C

#define FXOS_CTRL_REG_4             0x2D

#define FXOS_CTRL_REG_5             0x2E

#define FXOS_OFF_X                  0x2F

#define FXOS_OFF_Y                  0x30

#define FXOS_OFF_Z                  0x31

#define FXOS_TEMP                   0x51

#define FXOS_M_CTRL_REG_1           0x5B

#define FXOS_M_CTRL_REG_2           0x5C

#define FXOS_M_CTRL_REG_3           0x5D

//FXAS21002C

#define FXAS_ADDRESS_W              0x40

#define FXAS_ADDRESS_R              0x41

#define FXAS_STATUS                 0x00

#define FXAS_OUT_X_MSB              0x01

#define FXAS_F_SETUP                0x09

#define FXAS_F_EVENT                0x0A

#define FXAS_INT_SRC_FLAG           0x0B

#define FXAS_WHO_AM_I               0x0C

#define FXAS_ID                     0xD7

#define FXAS_CTRL_REG_0             0x0D

#define FXAS_RT_CFG                 0x0E

#define FXAS_TEMP                   0x12

#define FXAS_CTRL_REG_1             0x13

#define FXAS_CTRL_REG_2             0x14

#define FXAS_CTRL_REG_3             0x15

//Global variables

int FXAS_FIFO_FULL_FLAG = 0;

int FXOS_FIFO_FULL_FLAG = 0;

char fxos_data_1[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

char fxas_data_1[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

//Setup UART to PC

Serial pc(USBTX, USBRX);

//Setup I2C

I2C sensors(PTE0, PTE1);

//FXOS8700C Control Pins

InterruptIn fxos_int1_8700(PTD4); //INT1-8700

InterruptIn fxos_int2_8700(PTA4); //INT2-8700

//FXAS21002C Control Pins

InterruptIn fxas_int1_21002(PTA5);  //INT1-21002

InterruptIn fxas_int2_21002(PTA13); //INT2-21002

//SD File System

SDFileSystem sd(PTD2, PTD3, PTD1, PTD0, "sd");

////LED Setup                              

DigitalOut led_1(LED1, 1); //red

DigitalOut led_2(LED2, 1); //green

//DigitalOut led_3(LED3, 1); //blue         <- NB!! Wont play nice with SDFileSystem

//****************************************************************//

//Functions

int i2c_write(char address, char device_register, char data){

    sensors.start();

    sensors.write((char)address);

    sensors.write((char)device_register);

    sensors.write((char)data);

    sensors.stop();

    return 0;

}

int i2c_write(char address, char device_register, int stop){

    sensors.start();

    sensors.write((char)address);

    sensors.write((char)device_register);

    if(stop == 1){

        sensors.stop();

    }

    return 0;

}

char i2c_read(char address, char device_register){

    char data;

   

    sensors.start();

    sensors.write(address);

    sensors.write(device_register);

    sensors.start();

    sensors.write(address | 0x01);

    data = (char)sensors.read(0);

    sensors.stop();

    return data;

}

int i2c_write_verify(char address, char device_register, char data){

    char return_data;

    int return_val;

   

    sensors.start();

    sensors.write((char)address);

    sensors.write((char)device_register);

    sensors.write((char)data);

    sensors.stop();

   

    sensors.start();

    sensors.write(address);

    sensors.write(device_register);

    sensors.start();

    sensors.write(address | 0x01);

    return_data = sensors.read(0);

    sensors.stop();

   

    if (return_data == data){

        return_val = 0;

    }

    else{

        return_val = -1;

    }

    return return_val;

}

int fxas_init() {

    int return_val = 0;

    int sensor_id = 0;

 

    sensor_id = i2c_read(FXAS_ADDRESS_W, FXAS_WHO_AM_I);

//    pc.printf("Expected ID from FXAS21002C is 0xD7\n\r");

//    pc.printf("Returned value: %X\n\n\r", sensor_id);

   

    if (sensor_id == FXAS_ID){

        return_val = 0;

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_CTRL_REG_1, 0x00);

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_F_SETUP, 0x00);

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_F_SETUP, 0x54);

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_CTRL_REG_0, 0x03);

       

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_CTRL_REG_2, 0xC2);

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_CTRL_REG_3, 0x00);

        return_val += i2c_write_verify(FXAS_ADDRESS_W, FXAS_CTRL_REG_1, 0x13);      

    }

    else{

        return_val = -1;   

    }   

    return return_val;

}

   

int fxos_init() {

    int return_val = 0;

    int sensor_id = 0;

    

    sensor_id = i2c_read(FXOS_ADDRESS_W, FXOS_WHO_AM_I);

//    pc.printf("Expected ID from FXOS8700CQ is 0xC7\n\r");

//    pc.printf("Returned value: %X\n\n\r", sensor_id);

   

    if (sensor_id == FXOS_ID){

        return_val = 0;

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_CTRL_REG_1, 0x00);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_F_SETUP, 0x00);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_F_SETUP, 0x54);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_ASLP_COUNT, 0xFF);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_XYZ_DATA_CFG, 0x02);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_CTRL_REG_2, 0x00);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_CTRL_REG_3, 0x02);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_CTRL_REG_4, 0x41);  //Enable FIFO & DRDY Interrupts

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_CTRL_REG_5, 0x40);  //FIFO -> Int_1, DRDY -> Imt_2

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_M_CTRL_REG_1, 0x00);

        return_val += i2c_write_verify(FXOS_ADDRESS_W, FXOS_CTRL_REG_1, 0x21);

    }

    else{

        return_val = -1;   

    }

    return return_val;

}

//Interrupt for FXAS21002 INT_1

void read_fxas_data(){

//    //Read data from FXAS21002 sensor

    if(FXAS_FIFO_FULL_FLAG != 2){

        FXAS_FIFO_FULL_FLAG = 1;

    }

}

//Interrupt for FXOS8700S INT_1

void read_fxos_data(){

    //Read data from FXOS8700C sensor

    if(FXOS_FIFO_FULL_FLAG != 2){

        FXOS_FIFO_FULL_FLAG = 1;

    }

}

int main() {

    int initilised = 0;

    int index = 0;

    int test_index = 0;

    int fxos_data_flag_1 = 0;

    int fxas_data_flag_1 = 0;

   

    //Configure interrupts

    fxas_int1_21002.rise(&read_fxas_data);//FIFO -> Int_1

//    fxas_int2_21002.rise(&read_fxas_data);//DRDY -> Int_2

    fxos_int1_8700.rise(&read_fxos_data);//FIFO -> Int_1

//    fxos_int2_8700.rise(&read_fxos_data);//DRDY -> Int_2

   

    sensors.frequency(450000);

    pc.baud(115200);     

    mkdir("/sd/sensor_data", 0777);

    FILE *fp = fopen("/sd/sensor_data/data.txt", "w");

    if(fp == NULL) {

        error("Could not open file for write\n");

    }

    fprintf(fp, "Gyro X,\tGyro Y,\tGyro Z,\t\tAcc X,\tACC Y,\tACC Z\n\r\n\r\n\r\n\r");

    fclose(fp);

   

    //Initlilise the FXOS8700CQ Accelorometer & the FXAS21002C Gyroscope

    initilised = fxas_init() & fxos_init();

//    pc.printf("Returned value: %d\n\n\r", initilised);

 

    while(1) {

        if (FXOS_FIFO_FULL_FLAG == 1){//0.976mg * (fxos_data >> 2) = total g force (8g scale)

            FXOS_FIFO_FULL_FLAG = 0;

            i2c_write(FXOS_ADDRESS_W, FXOS_STATUS, 0);

            sensors.read(FXOS_ADDRESS_R, fxos_data_1, 139, false);//Reads the status register on every pass 0x06 -> 0x00

            fxos_data_flag_1 = 1;

        }

       

        if (FXAS_FIFO_FULL_FLAG == 1){//7.8125mdps * fxas_data = total degrees per second (250dps scale)

            FXAS_FIFO_FULL_FLAG = 0;

            i2c_write(FXAS_ADDRESS_W, FXAS_STATUS, 0);

            sensors.read(FXAS_ADDRESS_R, fxas_data_1, 139, false);//Reads the status register on the first if set to otherwise 0x06 -> 0x01

            fxas_data_flag_1 = 1;

        }

       

       

        if ((fxos_data_flag_1 == 1) && (fxas_data_flag_1 == 1)){

        //Store data on SD card   

            if (test_index == 0){// <--------- Just till a proper file closing system can be implemented

                fp = fopen("/sd/sensor_data/data.txt", "a");

                if(fp == NULL) {

                    error("Could not open file for write\n");

                }

            }

           

            for (index = 0; index < 139; index += 7){

                //move data to SD card

                fprintf(fp, "%d\t%d\t%d\t\t", ((int16_t)((fxos_data_1[(index + 1)] << 8) | fxos_data_1[(index + 2)]) >> 2),

                    ((int16_t)((fxos_data_1[(index + 3)] << 8) | fxos_data_1[(index + 4)]) >> 2),

                    ((int16_t)((fxos_data_1[(index + 5)] << 8) | fxos_data_1[(index + 6)]) >> 2));

                   

                fprintf(fp, "%d\t%d\t%d\n\r\n\r", ((int16_t)((fxas_data_1[(index + 1)] << 8) | fxas_data_1[(index + 2)])),

                    ((int16_t)((fxas_data_1[(index + 3)] << 8) | fxas_data_1[(index + 4)])),

                    ((int16_t)((fxas_data_1[(index + 5)] << 8) | fxas_data_1[(index + 6)])));

            }

           

            fxos_data_flag_1 = 0;

            fxas_data_flag_1 = 0;

            test_index++;

//            fprintf(fp, "\n\r\n\r\n\r\n\r\n\r\n\r");

            if (test_index == 30){// <--------- Just till a proper file closing system can be implemented

                fclose(fp);

                test_index = 0;;

            }

            for (int i = 0; i < 139; i++){

                fxos_data_1[i] = 0;

                fxas_data_1[i] = 0;

            }

        } 

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TomasVaverka
NXP TechSupport
NXP TechSupport

Hello Kas,

See my answer in your another thread - FXOS8700 data appears very noisy

Regards,

Tomas

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