problem in reading accelermeter sensor

[rajesh1987]

i have written code to read only accelerometer values from IMU9v2 sensor(combination of accelerometer, gyroscope and magnetometr), but it is not showing any result in serial terminal..
my code is:

#include <18f4550.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, parity=N, bits=8, errors)
#use i2c(master, sda=PIN_B0, scl=PIN_B1)


void main()
{
   unsigned int whoami;
   unsigned int conf1;
   unsigned int conf2;
   unsigned int raw_accel[6]; //to store raw acceleration data.
   int i = 7;
   //long int x_accel;
   int16 x_accel;
   int16 y_accel;
   int16 z_accel;

   //The G's
   float x_g;
   float y_g;
   float z_g;
   
   delay_ms(250); //Give things time to warm up
   
   //Now we're going to enable the accelerometer.
   i2c_start();
   i2c_write(0x32);
   i2c_write(0x20); //CTRL_REG1
   i = i2c_write(0x57);
   i2c_stop();
   
  i2c_start();
  i2c_write(0x32);
  i2c_write(0x23); //CTRL_REG4
  i = i2c_write(0x00);
  i2c_stop();

   printf("Accelerometer should be enabled... %u",i);

   //check to see if communications are ok. (Read WHOAMI)
   i2c_start();
   i2c_write(0x32);
   i2c_write(0x23); //WHOAMI---ctrlreg4
   i2c_start();
   i2c_write(0x33);
   whoami = i2c_read();
   i2c_stop();

   printf("\r\nWHOAMI = %3u \r\n",whoami); //print it out  on the serial link. 
   //If WHOAMI = 58 (3A) we're good. we can talk to accelerometer.

   i2c_start();
   i2c_write(0x32);
   i2c_write(0x20); //CTRL_REG1
   i2c_start();
   i2c_write(0x33);
   conf1 = i2c_read();
   i2c_stop();

   printf("\r\nCONF1 = %3u \r\n",conf1); //print it out  on the serial link.

   i2c_start();
   i2c_write(0x32);
   i2c_write(0x28 | 0x80);
   i2c_start();
   i2c_write(0x33);
   raw_accel[0] = i2c_read(1);
   raw_accel[1] = i2c_read(1);
   raw_accel[2] = i2c_read(1);
   raw_accel[3] = i2c_read(1);
   raw_accel[4] = i2c_read(1);
   raw_accel[5] = i2c_read(0);
   i2c_stop();

   //------------------------
   //Temporary! We're going to absolute value the accels.
   //------------------------
   raw_accel[1] &= 0x0F;
   raw_accel[3] &= 0x0F;
   raw_accel[5] &= 0x0F;

   x_accel = raw_accel[1];
   x_accel <<= 8;
   x_accel += raw_accel[0];

   y_accel = raw_accel[3];
   y_accel <<= 8;
   y_accel += raw_accel[2];

   z_accel = raw_accel[5];
   z_accel <<= 8;
   z_accel += raw_accel[4];

   printf("\r\n X: %Lu Y: %Lu Z: %Lu \r\n",x_accel,y_accel,z_accel);   

   //Calculate the G's
   x_g = (float)x_accel / 1024;
   y_g = (float)y_accel / 1024;
   z_g = (float)z_accel / 1024;

   printf("X: %g G Y: %g G Z: %g G \r\n", x_g, y_g, z_g);

   while(1)
   {
   i2c_start();
   i2c_write(0x32);
   i2c_write(0x28 | 0x80);
   i2c_start();
   i2c_write(0x33);
   raw_accel[0] = i2c_read(1);
   raw_accel[1] = i2c_read(1);
   raw_accel[2] = i2c_read(1);
   raw_accel[3] = i2c_read(1);
   raw_accel[4] = i2c_read(1);
   raw_accel[5] = i2c_read(0);
   i2c_stop();

   x_accel = raw_accel[1];
   x_accel <<= 8;
   x_accel += raw_accel[0];


   y_accel = raw_accel[3];
   y_accel <<= 8;
   y_accel += raw_accel[2];


   z_accel = raw_accel[5];
   z_accel <<= 8;
   z_accel += raw_accel[4];


//   printf("\r\n X: %Lu Y: %Lu Z: %Lu \r\n",x_accel,y_accel,z_accel);   

   //Calculate the G's
   x_g = (float)x_accel / 1024;
   y_g = (float)y_accel / 1024;
   z_g = (float)z_accel / 1024;

   printf("X: %g G Y: %g G Z: %g G \r\n", x_g, y_g, z_g);

   delay_ms(100);
}
}

 

[babar_ali]

Hi,
I've not used IMU9v2 but a couple of test comes to the mind. Are you able to read the device ID? if "yes" are you able to read it again say a looped read. If it answers it device ID once then there is a problem in ACK and NACK because it can't see it in your code.

   i2c_start();
   i2c_write(0x32);
   i2c_write(0x20); //CTRL_REG1
   i = i2c_write(0x57);
   i2c_stop();
   
  i2c_start();
  i2c_write(0x32);
  i2c_write(0x23); //CTRL_REG4
  i = i2c_write(0x00);
  i2c_stop();

If this does not solve your problem. Then paste your I2C code and i'll help you out with my I2C library for pic18 devices.

 

[rajesh1987]

i have tested with i2c bus scanner , in that it shows device address for all the 3 sensor in hyperterminal. i dont know how to read it as u mentioned above.. check whether the code as correct or not because have tried by changing the registers in the code..

regards

 

[babar_ali]

Hi,
Here is the code that i used to read ADXL345 accelrometer to read and write data.

void AdxlWrite(unsigned char DataByte, unsigned char RegisterAddress)
{
	I2CStart();
	writeI2C(SlavewriteAddress);            // I2C write address
	writeI2C(RegisterAddress);
	writeI2C(DataByte);
	I2CStop();
}
/**************************************************************************
** Read From Adxl 345 Accelrometer
** 
***************************************************************************/
void AdxlRead(char RegisterAddress, unsigned char BytesToRead)
{
	I2CStart();
	writeI2C(SlavewriteAddress);
	writeI2C(RegisterAddress);
	I2CReStart();
	writeI2C(SlaveReadAddress);
	for(loop = 0; loop < BytesToRead; loop++)
	{
		ADXLREAD[loop] = Read_I2C();
		if(loop == BytesToRead-1)
			NACK();
		else
			ACK();
	}
	I2CStop();
}

Also read I2C protocol from the following web

http://www.i2c-bus.org/i2c-primer/