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I want to use the complementary filter to get the roll and pitch angles using an IMU sensor with an stm32l4+ microcontroller but get (nan(0x400000). I get some values at first then it shows nan. this How I implement it.

/* Read the Data of the accelerometre*/
            accelerometer_reading(&MyAccel_DataDef,hspi3);
            gyroscope_reading(&MyGyro_DataDef,hspi3);
            /*Calculate roll (phi) and pitch (theta) angle using the Accelerometer */
            phiHat_acc_rad   = atanf(MyAccel_DataDef.y / MyAccel_DataDef.z);
            thetaHat_acc_rad = asin(MyAccel_DataDef.x  / GRAVITY);
            /*Transform body rates to Euler rates*/
            phiDot_rps   = MyGyro_DataDef.x + tanf(thetaHat_rad) * ( sinf(phiHat_rad) * MyGyro_DataDef.y + cosf(phiHat_rad) * MyGyro_DataDef.z);
            thetaDot_rps =                                           cosf(phiHat_rad) * MyGyro_DataDef.y - sinf(phiHat_rad) * MyGyro_DataDef.z ;
            
            /*Complementary filter*/
            phiHat_rad   =     COMP_FILT_ALPHA  *  phiHat_acc_rad + ( 1.0f - COMP_FILT_ALPHA) * (phiHat_rad +(SAMPLE_TIME_MS_USB / 1000.0f) * phiDot_rps);

            thetaHat_rad =     COMP_FILT_ALPHA  *  thetaHat_acc_rad + ( 1.0f - COMP_FILT_ALPHA) * (thetaHat_rad   +(SAMPLE_TIME_MS_USB / 1000.0f) * thetaDot_rps);

I test the accelerometer and the gyroscope and I get the roll and pitch angles with their problem but both i get this error.

bassem abidli
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  • You have some divisions in there. Are you sure you're not dividing by zero? You should check that the denominator is non-zero before each of those, and take appropriate action if it is. The tangent function `tanf()` is also undefined for certain input parameters. – pmacfarlane Jun 08 '23 at 17:57

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