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[PIC] MPU 6050 dspic33fj128gp802 summing operator problem

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orhanli1

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I use dspic33fj128gp802 and MPU6050 for my project. Microcontroller succesfully takes the data from sensors 6 channel and sends the data pc via UART. When i want to add "float 2.0" or "int 2" to accelerometer data for calibration it stops to send data to uart. I've tried all of data type combinations but it always fails. I only add one line of code to my source code but when i add, the code doesn't send data to PC. I use MikroC pro for dspic. The newly added line is shared below. This added line does not generate any compiling or debugging error.

accel_z = (float) accel_z + 2.0;

As a solution when i change the last line to accel_z = (float) accel_z / 2.0;

it succesfully divides the result to 2. As a summary, dividing operator works well but summing operator does not work.

I cannot find any solution. I am waiting for your considerations.

Thank you.
 

Edited Question is :

I use dspic33fj128gp802 and MPU6050 for my project. Microcontroller succesfully takes the data from sensors 6 channel and sends the data pc via UART. When i want to add "float 2.0" or "int 2" to accelerometer data for calibration it stops to send data to uart. I've tried all of data type combinations but it always fails. I only add one line of code to my source code but when i add, the code doesn't send data to PC. I use MikroC pro for dspic. The newly added line can be seen in source code in function of Extract_Readings. This newly added line does not generate any compiling or debugging error.

Code: 
accel_z = (float) accel_z + 2.0;

As a solution when i change the last line to:

Code: 
 accel_z = (float) accel_z / 2.0;

it succesfully divides the result to 2. As a summary, dividing operator works well but addition operator does not work.

I cannot find any solution. I am waiting for your considerations.

Thank you.

The source code is below:

Code C - [expand]
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#include "MPU_IMU_Register_Map.h"
 
    unsigned int raw_data[7];
 
    sbit INT at RB7_bit;
    sbit INT_Direction at TRISB7_bit;
 
    int gyro_x_temp, gyro_y_temp, gyro_z_temp, accel_x_temp, accel_y_temp, accel_z_temp, temp_raw;
    char i, buff, gyro_x_out[15], gyro_y_out[15], gyro_z_out[15], accel_x_out[15], accel_y_out[15], accel_z_out[15], temp_out[15];
    float temp, gyro_x, gyro_y, gyro_z, accel_x, accel_y, accel_z;
    
    void MCU_Init(){
      ADPCFG = 0xffff;
 
      TRISBbits.TRISB10 = 1;
      TRISBbits.TRISB11 = 0;
      Delay_ms(100);
 
      RPINR18bits.U1RXR = 10;
      RPOR5bits.RP11R   = 3;
 
      INT_Direction = 1;
      I2C1_Init(400000);
      Delay_ms(100);
 
      Delay_ms(100);
      UART1_Init_Advanced(19200, 1, 1, 1);
      Delay_ms(600);
 
      UART1_Write_Text("MCU Ready\n");
      Delay_ms(100);
    }
    void MPU_I2C_Write(unsigned char s_addr, unsigned char r_addr, unsigned char len, unsigned char *dat) {
     unsigned int i;
     I2C1_Start();                         // issue I2C start signal
     I2C1_Write(s_addr & 0xFE);            // send byte via I2C  (device address + W(&0xFE))
     I2C1_Write(r_addr);                   // send byte (address of EEPROM location)
     for (i = 0 ; i < len ; i++){
      I2C1_Write(*dat++);                 // send data (data to be written)
     }
     I2C1_Stop();                          // issue I2C stop signal
 
    }
 
    void MPU_I2C_Read(unsigned char s_addr, unsigned char r_addr, unsigned char len, unsigned char *dat) {
     unsigned int i;
     I2C1_Start();                         // issue I2C start signal
     I2C1_Write(s_addr & 0xFE);            // send byte via I2C  (device address + W(&0xFE))
     I2C1_Write(r_addr);                   // send byte (data address)
     I2C1_Restart();                       // issue I2C signal repeated start
     I2C1_Write(s_addr | 0x01);            // send byte (device address + R(|0x01))
     for (i = 0; i < (len-1); i++){
      *dat++ = I2C1_Read(_I2C_ACK);       // Read the data (acknowledge)
      }
      *dat = I2C1_Read(_I2C_NACK);          // Read the data (NO acknowledge)
     I2C1_Stop();                          // issue I2C stop signal
     }
 
    void MPU_I2C_Read_Int(unsigned char s_addr, unsigned char r_addr, unsigned char len, unsigned char *dat) {
      unsigned int i;
      unsigned short *pt;
      I2C1_Start();                         // issue I2C start signal
      I2C1_Write(s_addr & 0xFE);            // send byte via I2C  (device address + W(&0xFE))
      I2C1_Write(r_addr);                   // send byte (data address)
      I2C1_Restart();                       // issue I2C signal repeated start
      I2C1_Write(s_addr | 0x01);            // send byte (device address + R(|0x01))
      for (i = 0 ; i < ((len << 1)-1) ; i++){
       if (i%2) {
         pt = pt - 1;
       }
       else {
         pt = dat + i + 1;
       }
        *pt = I2C1_Read(_I2C_ACK);          // Read the data (acknowledge)
      }
      *(pt - 1) = I2C1_Read(_I2C_NACK);     // Read the data (NO acknowledge)
      I2C1_Stop();                          // issue I2C stop signal
    }
 
 
    void MPU_Init(){
     MPU_I2C_Write(mpu_I2C_ADDR, mpu_rm_PWR_MGMT_1 , 1, 0x80);
     Delay_ms(100);
     MPU_I2C_Write(mpu_I2C_ADDR, mpu_rm_PWR_MGMT_1 , 1, 0x00);
     Delay_ms(100);
 
     MPU_I2C_Write(mpu_I2C_ADDR, mpu_rm_FIFO_EN , 1, 0x78);
     Delay_ms(100);
 
     MPU_I2C_Write(mpu_I2C_ADDR, mpu_rm_INT_ENABLE , 1, 0x10);
     Delay_ms(100);
 
     MPU_I2C_Read (mpu_I2C_ADDR, mpu_rm_ACCEL_CONFIG, 1, &raw_data);
     Delay_ms(100);
 
 
     MPU_I2C_Read (mpu_I2C_ADDR, mpu_rm_INT_ENABLE, 1, &raw_data);
     Delay_ms(100);
 
     raw_data[0] |= 0x11;
     MPU_I2C_Write(mpu_I2C_ADDR, mpu_rm_INT_ENABLE, 1, &raw_data[0]);
     Delay_ms(100);
     UART1_Write_Text("MPU6050 Hazir\n");
 
    }
    void Extract_Readings() {
 
     accel_x_temp = raw_data[0];
     accel_x = (float)accel_x_temp / 2048.0;
     accel_y_temp = raw_data[1];
     accel_y = (float)accel_y_temp / 2048.0;
     accel_z_temp = raw_data[2];
     accel_z = (float)accel_z_temp / 2048.0;
     //accel_z = (float) accel_z + 2.0; When this line deleted or changed to accel_z = (float) accel_z /2.0, code works well
 
     temp_raw = raw_data[3];
 
     temp = (float)temp_raw / 325.0;
 
     gyro_x_temp = raw_data[4];
     gyro_x = (float)gyro_x_temp / 131.0;
     gyro_y_temp = raw_data[5];
     gyro_y = (float)gyro_y_temp / 131.0;
 
     gyro_z_temp = raw_data[6];
     gyro_z = (float)gyro_z_temp / 131.0;
 
    }
    void Convert_Readings_To_String() {
 
    FloatToStr(accel_x, accel_x_out);
    FloatToStr(accel_y, accel_y_out);
    FloatToStr(accel_z, accel_z_out);
 
 
    FloatToStr(temp, temp_out);
 
 
    FloatToStr(gyro_x, gyro_x_out);
    FloatToStr(gyro_y, gyro_y_out);
    FloatToStr(gyro_z, gyro_z_out);
 
    }
 
 
    void Print_Readings() {
 
     Delay_ms(500);
     UART1_Write_Text("\nGyro readings:\n");
     UART1_Write(0x0D);
     UART1_Write_Text("\nx = \n");
     UART1_Write_Text(gyro_x_out);
     UART1_Write(0x0D);
     UART1_Write_Text("\ny = \n");
     UART1_Write_Text(gyro_y_out);
     UART1_Write(0x0D);
     UART1_Write_Text("\nz = \n");
     UART1_Write_Text(gyro_z_out);
     UART1_Write(0x0D);
     UART1_Write(0x0D);
     UART1_Write(0x0D);
 
 
     UART1_Write_Text("\nAccel readings:\n");
     UART1_Write(0x0D);
     UART1_Write_Text("\nx = \n");
     UART1_Write_Text(accel_x_out);
     UART1_Write(0x0D);
     UART1_Write_Text("\ny = \n");
     UART1_Write_Text(accel_y_out);
     UART1_Write(0x0D);
     UART1_Write_Text("\nz = \n");
     UART1_Write_Text(accel_z_out);
     UART1_Write(0x0D);
     UART1_Write(0x0D);
     UART1_Write(0x0D);
 
 
     UART1_Write_Text("\nTemperature readings (Celsius) = ");
     UART1_Write_Text(temp_out);
     UART1_Write(0x0D);
     UART1_Write(0x0D);
     UART1_Write(0x0D);
     Delay_ms(1000);
 
 
    }
    void main() {
 
     MCU_Init();
     MPU_Init();
     while(1) {
     while(INT != 1)
      ;
     MPU_I2C_Read_Int(mpu_I2C_ADDR, mpu_rm_ACCEL_XOUT_H, 7, &raw_data);
     Extract_Readings();
     Convert_Readings_To_String();
     Print_Readings();
    }
     
     
    }
 
Last edited by a moderator:

My *guess* is that it is a value range error.
How are you detecting that there is an error?
What I would be doing is using a debugger to single step through the code and see when something goes wrong.
I suspect that the line in question is not actually causing the problem and that the value that is stored in the 'accel_z' variable will be correct. However, when you get to the 'FLoatToStr' cal to convert 'accel_z' to 'accel_z_out' that the generated string is not as expected.
Looking at your code (and knowing nothing about the range of correct values) I would take it that the 'accel_z' value should be between -1 and +1 (or perhaps 0 and +1) with an assumed 11 bits of accuracy. However, when you add the '2.0' the range is +1 to +3 and for some reason this is causing the generated string to be too long and possibly overflowing the buffer.
(By the way, I do not use your compiler and so this is based purely on my general experience.)
However single-stepping through you code will help identify the problem for you.
Susan
 

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