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LIS3DH with strange output values

Question asked by Rafael Costa on Feb 2, 2018
Latest reply on Feb 7, 2018 by Rafael Costa

Dear all,


   For one important project i need to detect the human falls. I am using the LIS3DH accelerometer configured as the following manner:  


        CTRL_REG1=0x77 //ODR=400 Hz, high-resolution mode/normal mode, ZYX axis enabled

        CTRL_REG2=0x01 // High pass filter enabled for AOI function on interrupt 1

        CTRL_REG3=0x40 // IA1 interrupt on INT1

        CTRL_REG4=0x84 // Output register not updated until MSB and LSB reading, high-resolution enabled

        INT1_THS=0x20      // 16mgx32=0,512g

        INT1_CFG=0x2A     // Or combination of interrupt events. Enable interrupt generation on X, Y and Z high event.


When the accelerometer has just the gravity acceleration applied along the z-axis, the output registers OUT_X_L, OUT_X_H, OUT_Y_L, OUT_Y_H, OUT_Z_L have the value 0, the register OUT_Z_H has the value 255.


When i apply acceleration the output registers OUT_X_L,OUT_X_H,OUT_Y_L,OUT_Y_H,OUT_Z_L just assume one of the following values: 64;128,192. The register OUT_Z_H have always the value 255. Obviously the values should vary between 0 and 255. When i apply acceleration is generated one interrupt on the pin INT1 detected by one microcontroller. On attachment i send the values of the output registers and the calculated acceleration.


Any help will be very appreciated.

Best regards,

Rafael Costa