G-sensor FXLS8471Q

monstor — Tue, 03 Feb 2026 22:19:10 GMT

I follow the AN4692 to configure my G-sensor. The output seems is normal. When we roll over the G-sensor, there is a normal output. However, after that the G-sensor output would become zero again immediately. We already disable the Auto-wake/sleep mode and low power mode. Please help.

Re: G-sensor FXLS8471Q

TomasVaverka — Tue, 29 Sep 2015 08:37:54 GMT

Hi Henry,

It is hard to say where the problem might be. If you posted here your source code and ideally also timing diagrams from a logic analyzer, I might be able to help you in your investigation.

Meanwhile, you may find useful my simple FXLS8471Q bare-metal example code or another example code illustrating the use of the vector-magnitude function.

Regards,

Tomas

PS: If my answer helps to solve your question, please mark it as "Correct" or “Helpful”. Thank you.

Re: G-sensor FXLS8471Q

monstor — Tue, 29 Sep 2015 08:52:39 GMT

Dear Tomas,

Below is my source code.

void Initial_GSensor(void)
{
     CS_B_PutVal(1);//int the CS to High

      GSensor_Write_Addr_Cmd(XYZ_DATA_CFG, 0x12); // +/-8g range with ~0.976mg/LSB
//     Set_Roll_Over();
//     Set_Transient_Detection();
       GSensor_Write_Addr_Cmd(CTRL_REG1, 0x39);    // ODR = 1.56Hz, Normal mode, Active mode
       GSensor_Write_Addr_Cmd(CTRL_REG2, 0x02);    // Reset, High Resolution mode
//     Get_GSensor_Calibration();
}

void Get_GSensor_XYZ(void)
{

    GSensor_Read_Addr_Cmd(OUT_X_MSB, 7);
    X_MSB = GSensor_Data[1];
    X_LSB = GSensor_Data[2];
    Y_MSB = GSensor_Data[3];
    Y_LSB = GSensor_Data[4];
    Z_MSB = GSensor_Data[5];
    Z_LSB = GSensor_Data[6];

    G_Sensor.Xout_14bit = ((X_MSB << 8) | (X_LSB))>>2;
    G_Sensor.Yout_14bit = ((Y_MSB << 8) | (Y_LSB))>>2;
    G_Sensor.Zout_14bit = ((Z_MSB << 8) | (Z_LSB))>>2;

    if(G_Sensor.Xout_14bit >= TWO_COMPLEMENT){
      X = ((X_MSB << 8) | (X_LSB))>>2;                      // flip all the 14 bits
      X = (X ^ 0x3FFF) + 1;
      G_Sensor.Xout_g = X * SENSITIVITY * (-1);             // Compute X-axis output value in g's
    }else{
      G_Sensor.Xout_g = G_Sensor.Xout_14bit*SENSITIVITY;    // Compute X-axis output value in g's
    }

    if(G_Sensor.Yout_14bit >= TWO_COMPLEMENT){
      Y = ((Y_MSB << 8) | (Y_LSB))>>2;                      // flip all the 14 bits
      Y = (Y ^ 0x3FFF) + 1;
      G_Sensor.Yout_g = Y * SENSITIVITY * (-1);             // Compute Y-axis output value in g's
    }else{
      G_Sensor.Yout_g = G_Sensor.Yout_14bit*SENSITIVITY;    // Compute Y-axis output value in g's
    }

    if(G_Sensor.Zout_14bit >= TWO_COMPLEMENT){
      Z = ((Z_MSB << 8) | (Z_LSB))>>2;                      // flip all the 14 bits
      Z = (Z ^ 0x3FFF) + 1;
      G_Sensor.Zout_g = Z * SENSITIVITY * (-1);             // Compute Z-axis output value in g's
    }else{
      G_Sensor.Zout_g = G_Sensor.Zout_14bit*SENSITIVITY;    // Compute Z-axis output value in g's
    }
}

void Get_GSensor_Calibration(void)
{

    GSensor_Write_Addr_Cmd(CTRL_REG1, 0x18);   //Set device in 100 Hz ODR, Standby

    GSensor_Read_Addr_Cmd(OUT_X_MSB, 7);
    X_MSB = GSensor_Data[1];
    X_LSB = GSensor_Data[2];
    Y_MSB = GSensor_Data[3];
    Y_LSB = GSensor_Data[4];
    Z_MSB = GSensor_Data[5];
    Z_LSB = GSensor_Data[6];

    G_Sensor.Xout_14bit = ((X_MSB << 8) | (X_LSB))>>2;
    G_Sensor.Yout_14bit = ((Y_MSB << 8) | (Y_LSB))>>2;
    G_Sensor.Zout_14bit = ((Z_MSB << 8) | (Z_LSB))>>2;

    X_offset = G_Sensor.Xout_14bit / 8 * (-1);
    Y_offset = G_Sensor.Yout_14bit / 8 * (-1);
    Z_offset = (G_Sensor.Zout_14bit - SENSITIVITY) / 8 * (-1);

    GSensor_Write_Addr_Cmd(CTRL_REG1, 0x39);    // ODR = 1.56Hz, Reduced noise, Active mode

}

void GSensor_Read_Addr_Cmd(char Addr,word len)
{
isoSPI1_TComData temp_char;
word i;

Delay_ms_GSensor(1);

CS_B_PutVal(0);//CS low

Delay_ms_GSensor(1);

Check_Value = 1;
TimeOut_CNT = 0;
while( (Check_Value != 0) && (TimeOut_CNT < 3000)){
    Check_Value = isoSPI1_SendChar( ((~0x80) & Addr) );   // R/W, ADDR[6], ADDR[5], ADDR[4], ADDR[3], ADDR[2], ADDR[1], ADDR[0]
    TimeOut_CNT++;
}

Check_Value = 1;
TimeOut_CNT = 0;
while( (Check_Value != 0) && (TimeOut_CNT < 3000)){
    Check_Value = isoSPI1_SendChar(Addr);                 // ADDR[7], X, X, X, X, X, X, X
    TimeOut_CNT++;
}

Delay_ms_GSensor(1);

for(i=0;i<len;i++)
{
    isoSPI1_SendChar(0);                  // dummy

    Check_Value = 1;
    TimeOut_CNT = 0;
    while( (Check_Value != 0) && (TimeOut_CNT < 3000)){
      Check_Value = isoSPI1_RecvChar(&temp_char);         // DATA[7], DATA[6], DATA[5], DATA[4], DATA[3], DATA[2], DATA[1], DATA[0]
      TimeOut_CNT++;
    }
    GSensor_Data[i] = temp_char;
}

Delay_ms_GSensor(1);

CS_B_PutVal(1);//CS High

Delay_ms_GSensor(1);

}

void GSensor_Write_Addr_Cmd(char Addr,char data)
{

Delay_ms_GSensor(1);

CS_B_PutVal(0);//CS low

Delay_ms_GSensor(1);

Check_Value = 1;
TimeOut_CNT = 0;
while( (Check_Value != 0) && (TimeOut_CNT < 3000)){
    Check_Value = isoSPI1_SendChar( ((0x80) | Addr) );   // R/W, ADDR[6], ADDR[5], ADDR[4], ADDR[3], ADDR[2], ADDR[1], ADDR[0]
    TimeOut_CNT++;
}

Check_Value = 1;
TimeOut_CNT = 0;
while( (Check_Value != 0) && (TimeOut_CNT < 3000)){
    Check_Value = isoSPI1_SendChar(Addr);                // ADDR[7], X, X, X, X, X, X, X
    TimeOut_CNT++;
}

Check_Value = 1;
TimeOut_CNT = 0;
while( (Check_Value != 0) && (TimeOut_CNT < 3000)){
    Check_Value = isoSPI1_SendChar(data);                // DATA[7], DATA[6], DATA[5], DATA[4], DATA[3], DATA[2], DATA[1], DATA[0]
    TimeOut_CNT++;
}

Delay_ms_GSensor(1);

CS_B_PutVal(1);//CS High

Delay_ms_GSensor(1);

}

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