ADXl345 - number of Samples for ODR - 3200

Hi Srinivasa,

It seems like you may be measuring your rate of data acquisition as opposed to the ODR of the ADXL345? How exactly did you measure the above results?

The ADXL34x devices produce data using an internal clock, which is independent of your communication signals (when the timing of those signals is within datasheet-provided guidelines). The ADXL345 uses an RC oscillator for clock generation with an accuracy of +/-10% over temperature and accounting for any drift over time. When new data is ready, the data-ready signal (when configured correctly) will pulse. This signal provides an opportunity for you to measure the ODR.

If you can measure the time between DATA_READY interrupts in your set-up, you may be able to get a more accurate ODR measurement. The acceleration data is sampled at a rate given by the ODR configured by the user (register 0x2C BW_RATE). If what you are trying to achieve is to acquire data in a synchronous way, you can do so by mapping the DATA_READY bit of register INT_SOURCE (0x30) to an interrupt pin, and using this pin for synchronization. Any time a set of data (X,Y,Z) is ready, DATA_READY will be set to HIGH. Once you read the registers 0x32 to 0x37, DATA_READY will automatically set to low. This is well explained in page 20 of the datasheet.

I hope this helps.

Chris

Dear Chris, 

Thank you for your support. 

We are acquiring the data in a synchronous way only by  mapping the DATA_READY bit of register INT_SOURCE (0x30) to an interrupt pin (INT2). 

Below we are providing the code for your reference, If you have any feedback on this , please let me know. 

void adxl345_setInterrputs(adxl345_int intType, bool intPin)
{
adxl345_setRegBit(ADXL345_INT_ENABLE, intType, ENABLE);
adxl345_setRegBit(ADXL345_INT_MAP, intType, intPin);
}

uint8_t adxl345_readAndClearInterrupts(void)
{
uint8_t regVal;
adxl345_RegRead(ADXL345_INT_SOURCE, &regVal, 1);
return regVal;
}

main()
{
while(1)
{
HAL_NVIC_SetPriority(EXTI9_5_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(EXTI9_5_IRQn);
adxl345_setInterrputs(ADXL345_DATAREADY, ADXL345_INT2_PIN);
adxl345_readAndClearInterrupts();

HAL_Delay(1000);
adxl345_deleteInterrupt(ADXL345_DATAREADY);
HAL_NVIC_DisableIRQ(EXTI9_5_IRQn);
printf("Data Aquisition time Finished\r\n");
adxl345_setMeasureMode(DISABLE);
}
}

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
if(GPIO_Pin == INT2_PIN) {
FuncOn_Data_Aquisition();

}
}

Thanks

Srinivas