AnsweredAssumed Answered

ADXL345 - Data Output

Question asked by JOSEF on Nov 26, 2012
Latest reply on Nov 27, 2012 by Kevin.G

Hello,

 

i have been experimenting with the ADXL345 for a while now and cannot get any valid output from the data registers. The output data is always in the range of of +-512 (regardless the sensor is set to FULL or 10bit resolution mode). The value of Z-Axis (corresponding to the earth gravity direction) is always around 256. Multiplied by the 3.9mg/LSB, the output of 1G is correct. But due to the sensor doesn`t output beyond 512 i cannot measure any values above 2G.

 

Here are some sample outputs of the Z-AXIS with different settings:

 

// 2G FULL RESOLUTION

 

/*0x2C*/ BW_RATE     = 00001011   

/*0x2D*/ POWER_CTL   = 00001000   

/*0x31*/ DATA_FORMAT = 00001000   

 

OUTPUT OF Z  = [00000001 00000000] = 256

 

// 16G FULL RESOLUTION

 

/*0x2C*/ BW_RATE     = 00001011   

/*0x2D*/ POWER_CTL   = 00001000   

/*0x31*/ DATA_FORMAT = 00001011   

 

OUTPUT OF Z = [00000000 11111111] = 255

 

// 16G FULL RESOLUTION WITH SELFTEST ON

 

/*0x2C*/ BW_RATE     = 00001011   

/*0x2D*/ POWER_CTL   = 00001000   

/*0x31*/ DATA_FORMAT = 10001011   

 

OUTPUT OF Z = [00000000 11111100] = 252

 

Maybe one of you can confirm that the output data above is approximately correct regarding the selected settings? OR is there something wrong?

 

Thanks a lot for your advice.

Outcomes