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I'm trying to interface mpu6050 module with pic16f886 microcontroller. But, i'm getting x-axis, y-axis and z-axis as 0. Why is there no change in readings even when i move my mpu? enter image description here

edit: This is the raw data xh,xl,yh,yl,zh and zl are 255. enter image description here

source.c

#include <xc.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
#include "all_header.h"

void usart_init(){
    TRISC6=0;
    TRISC7=1;
//    SPBRG=_XTAL_FREQ/(16*baud) -1;
    SPBRG=25;                                                                   //pg.no - 163
    TXSTAbits.BRGH=1;
    TXSTAbits.SYNC=0;
    RCSTAbits.SPEN=1;
    TXSTAbits.TXEN=1;
    RCSTAbits.CREN=1;
    TXSTAbits.TX9=0;
    RCSTAbits.RX9=0;
    RCSTAbits.FERR = 0;     // Disable framing error
    RCSTAbits.OERR = 0;     // Disable overrun error

}

void usart_send_byte(char bt){
    while(TXIF==0);
    TXREG=bt;
}


void usart_send_string(char* str) {
    while(*str!= '\0')
        usart_send_byte(*str++);
}

//i2c

void i2c_init(void){
    TRISC3=1;
    TRISC4=1;

    SSPADD= ((_XTAL_FREQ/4)/I2C_SPEED)-1;
    SSPSTAT=0x80;
    SSPCON=0x28;
    SSPCON2=0x00;
}

void i2c_start_write(char slave_add){
    SSPCON2bits.SEN = 1;            /* Send START condition */
    while(SSPCON2bits.SEN);         /* Wait for completion of START */
    i2c_write(slave_add);           /* Write slave device address with write to communicate */

}

void i2c_stop(void){
    SSPCON2bits.PEN=1;
    while(!SSPIF);
    SSPIF=0;
}

void i2c_write(unsigned char data){
    SSPBUF=data;
    while(!SSPIF);
    SSPIF=0;

}

unsigned char i2c_read(unsigned ack){
    SSPCON2bits.RCEN=1;
    while(!SSPIF);
    SSPIF=0;

    return SSPBUF;
}


void mpu_init(){

    i2c_start_write(0xD0);                                                      //slave write address
    i2c_write(SMPLRT_DIV);                                                      //write to sample rate register(write to this address)
    i2c_write(0x07);                                                            //100KHZ sample rate(write to data)
    i2c_stop();

    i2c_start_write(0xD0);                                                      //slave write address
    i2c_write(PWR_MGMT_1);
    i2c_write(0x01);                                                            //x-axis gyro reference frequency
    i2c_stop();

    i2c_start_write(0xD0);                                                      //slave write address
    i2c_write(CONFIG);
    i2c_write(0x01);                                                            //fs=1KHZ
    i2c_stop();

    i2c_start_write(0xD0);                                                      //slave write address
    i2c_write(GYRO_CONFIG);
    i2c_write(0x18);                                                            //full scale range +/- 2000 deg/c
    i2c_stop();

    i2c_start_write(0xD0);                                                      //slave write address
    i2c_write(INT_ENABLE);
    i2c_write(0x01);
    i2c_stop();
}



void main(){

    char buffer[20];
    int  xh,xl,yh,yl,zh,zl,ax,ay,az;
    float xa,ya,za;
    OSCCON=0x64;                                                                
    usart_init();
    i2c_init();
    mpu_init();


    // Read accelerometer values out from H and L registers
    while(1){
    i2c_start_write(0xD0);
    i2c_write(ACCEL_XOUT_H);
    i2c_write(0xD1);
    xh=i2c_read(0);
    i2c_stop();

    i2c_start_write(0xD0);
    i2c_write(ACCEL_XOUT_L);
    i2c_write(0xD1);
    xl=i2c_read(0);
    i2c_stop();

    i2c_start_write(0xD0);
    i2c_write(ACCEL_YOUT_H);
    i2c_write(0xD1);
    yh=i2c_read(0);
    i2c_stop();

    i2c_start_write(0xD0);
    i2c_write(ACCEL_YOUT_L);
    i2c_write(0xD1);
    yl=i2c_read(0);
    i2c_stop();

    i2c_start_write(0xD0);
    i2c_write(ACCEL_ZOUT_H);
    i2c_write(0xD1);
    zh=i2c_read(0);
    i2c_stop();

    i2c_start_write(0xD0);
    i2c_write(ACCEL_ZOUT_L);
    i2c_write(0xD1);
    zl=i2c_read(0);
    i2c_stop();


    // Convert received data
    ax = ( xh<<8 | xl );
    ay= ( yh<<8 | yl );
    az = ( zh<<8 | zl );

    xa =(float)ax/16384.0;
    ya =(float)ay/16384.0;
    za =(float)az/16384.0;

        sprintf(buffer,"ax=%.2f g\r\n",xa);                                       //Take values in buffer and send it over to Usart
        usart_send_string(buffer);

        sprintf(buffer,"ay=%.2f g\r\n",ya);                                       
        usart_send_string(buffer);

        sprintf(buffer,"az=%.2f g\r\n",za);                                       
        usart_send_string(buffer);
}
}

allheader.h

#ifndef ALL_HEADER_H
#define ALL_HEADER_H

#pragma config FOSC = INTRC_CLKOUT       
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled and can be enabled by SWDTEN bit of the WDTCON register)
#pragma config PWRTE = ON       // Power-up Timer Enable bit (PWRT enabled)
#pragma config MCLRE = ON       // RE3/MCLR pin function select bit (RE3/MCLR pin function is MCLR)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown Out Reset Selection bits (BOR enabled)
#pragma config IESO = OFF        // Internal External Switchover bit (Internal/External Switchover mode is enabled)
#pragma config FCMEN = OFF       // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is enabled)
#pragma config LVP = OFF        // Low Voltage Programming Enable bit (RB3 pin has digital I/O, HV on MCLR must be used for programming)

// CONFIG2
#pragma config BOR4V = BOR40V   // Brown-out Reset Selection bit (Brown-out Reset set to 4.0V)
#pragma config WRT = OFF        // Flash Program Memory Self Write Enable bits (Write protection off)


#include <xc.h> 
#define _XTAL_FREQ 4000000
#define I2C_SPEED 100000
#define baud 9600

#define XG_OFFS_TC 0x00
#define YG_OFFS_TC 0x01
#define ZG_OFFS_TC 0x02
#define X_FINE_GAIN 0x03
#define Y_FINE_GAIN 0x04
#define Z_FINE_GAIN 0x05
#define XA_OFFS_H 0x06 
#define XA_OFFS_L_TC 0x07
#define YA_OFFS_H 0x08 
#define YA_OFFS_L_TC 0x09
#define ZA_OFFS_H 0x0A 
#define ZA_OFFS_L_TC 0x0B
#define XG_OFFS_USRH 0x13
#define XG_OFFS_USRL 0x14
#define YG_OFFS_USRH 0x15
#define YG_OFFS_USRL 0x16
#define ZG_OFFS_USRH 0x17
#define ZG_OFFS_USRL 0x18
#define SMPLRT_DIV 0x19
#define CONFIG 0x1A
#define GYRO_CONFIG 0x1B
#define ACCEL_CONFIG 0x1C
#define FF_THR 0x1D
#define FF_DUR 0x1E
#define MOT_THR 0x1F
#define MOT_DUR 0x20
#define ZRMOT_THR 0x21
#define ZRMOT_DUR 0x22
#define FIFO_EN 0x23
#define I2C_MST_CTRL 0x24
#define I2C_SLV0_ADDR 0x25
#define I2C_SLV0_REG 0x26
#define I2C_SLV0_CTRL 0x27
#define I2C_SLV1_ADDR 0x28
#define I2C_SLV1_REG 0x29
#define I2C_SLV1_CTRL 0x2A
#define I2C_SLV2_ADDR 0x2B
#define I2C_SLV2_REG 0x2C
#define I2C_SLV2_CTRL 0x2D
#define I2C_SLV3_ADDR 0x2E
#define I2C_SLV3_REG 0x2F
#define I2C_SLV3_CTRL 0x30
#define I2C_SLV4_ADDR 0x31
#define I2C_SLV4_REG 0x32
#define I2C_SLV4_DO 0x33
#define I2C_SLV4_CTRL 0x34
#define I2C_SLV4_DI 0x35
#define I2C_MST_STATUS 0x36
#define INT_PIN_CFG 0x37
#define INT_ENABLE 0x38
#define DMP_INT_STATUS 0x39
#define INT_STATUS 0x3A
#define ACCEL_XOUT_H 0x3B
#define ACCEL_XOUT_L 0x3C
#define ACCEL_YOUT_H 0x3D
#define ACCEL_YOUT_L 0x3E
#define ACCEL_ZOUT_H 0x3F
#define ACCEL_ZOUT_L 0x40
#define TEMP_OUT_H 0x41
#define TEMP_OUT_L 0x42
#define GYRO_XOUT_H 0x43
#define GYRO_XOUT_L 0x44
#define GYRO_YOUT_H 0x45
#define GYRO_YOUT_L 0x46
#define GYRO_ZOUT_H 0x47
#define GYRO_ZOUT_L 0x48
#define EXT_SENS_DATA_00 0x49
#define EXT_SENS_DATA_01 0x4A
#define EXT_SENS_DATA_02 0x4B
#define EXT_SENS_DATA_03 0x4C
#define EXT_SENS_DATA_04 0x4D
#define EXT_SENS_DATA_05 0x4E
#define EXT_SENS_DATA_06 0x4F
#define EXT_SENS_DATA_07 0x50
#define EXT_SENS_DATA_08 0x51
#define EXT_SENS_DATA_09 0x52
#define EXT_SENS_DATA_10 0x53
#define EXT_SENS_DATA_11 0x54
#define EXT_SENS_DATA_12 0x55
#define EXT_SENS_DATA_13 0x56
#define EXT_SENS_DATA_14 0x57
#define EXT_SENS_DATA_15 0x58
#define EXT_SENS_DATA_16 0x59
#define EXT_SENS_DATA_17 0x5A
#define EXT_SENS_DATA_18 0x5B
#define EXT_SENS_DATA_19 0x5C
#define EXT_SENS_DATA_20 0x5D
#define EXT_SENS_DATA_21 0x5E
#define EXT_SENS_DATA_22 0x5F
#define EXT_SENS_DATA_23 0x60
#define MOT_DETECT_STATUS 0x61
#define I2C_SLV0_DO 0x63
#define I2C_SLV1_DO 0x64
#define I2C_SLV2_DO 0x65
#define I2C_SLV3_DO 0x66
#define I2C_MST_DELAY_CTRL 0x67
#define SIGNAL_PATH_RESET 0x68
#define MOT_DETECT_CTRL 0x69
#define USER_CTRL 0x6A
#define PWR_MGMT_1 0x6B
#define PWR_MGMT_2 0x6C
#define BANK_SEL 0x6D
#define MEM_START_ADDR 0x6E
#define MEM_R_W 0x6F
#define DMP_CFG_1 0x70
#define DMP_CFG_2 0x71
#define FIFO_COUNTH 0x72
#define FIFO_COUNTL 0x73
#define FIFO_R_W 0x74
#define WHO_AM_I 0x75

void i2c_init(void);
void i2c_stop(void);
void i2c_start_write(char);
void i2c_write(unsigned char);
unsigned char i2c_read(unsigned);



void usart_init();
void usart_send_byte(char);
void usart_send_string(char*);


void mpu_init();



#endif  /* ALL_HEADER_H */
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  • \$\begingroup\$ @BruceAbbott : This is the simplified code, where i'm just checking accelerometer values, Which as you can see, doesn't change. Hope you don't mind tagging you. \$\endgroup\$ – Captain aaloo reportin' in Feb 5 at 10:33
  • \$\begingroup\$ havve you verified that xh, yh, zh are what you expect? \$\endgroup\$ – Marcus Müller Feb 5 at 10:34
  • \$\begingroup\$ @MarcusMüller: It's constant .. xh = 255, yh = 255, zh =255. No change even if i move/rotate my mpu. \$\endgroup\$ – Captain aaloo reportin' in Feb 5 at 10:42
  • 1
    \$\begingroup\$ So, that's maybe something you want to mention in your question? Give as much debugging info as possible, and simplify your code as far as possible to still be able to figure out what's wrong. \$\endgroup\$ – Marcus Müller Feb 5 at 10:55
  • 2
    \$\begingroup\$ @Captain - Hi, you now have 3 open questions on the same topic: this one, "USART displays only half values when VCC is plugged in and repeats the same after VCC is removed" and "Nothing seen on serial monitor - MPU6050 with pic16f886". They seem to have only small differences. Having multiple similar open questions will not go well here, as you are wasting readers' time, looking at different versions of your code, but new info is revealed elsewhere. Stick with one question & update it. \$\endgroup\$ – SamGibson Feb 5 at 14:16
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Try to change on the init code:

i2c_start_write(0xD0);                                                      //slave write address
i2c_write(PWR_MGMT_1);
i2c_write(0x01);                                                            //x-axis gyro reference frequency
i2c_stop();

to

i2c_start_write(0xD0);                                                      //slave write address
i2c_write(PWR_MGMT_1);
i2c_write(0x00);                                                            //x-axis gyro reference frequency
i2c_stop();

to use the internal oscillator.

Also you don't seem to use interrupt, set

i2c_start_write(0xD0);                                                      //slave write address
i2c_write(INT_ENABLE);
i2c_write(0x01);
i2c_stop();

to

i2c_start_write(0xD0);                                                      //slave write address
i2c_write(INT_ENABLE);
i2c_write(0x00);
i2c_stop();
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