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MMA8451 accelerometer

ankur shah

i am using p89v51rd2bn microcontroller and have interfaced MMA8451 accelerometer with it using i2c bus.
The problem i am facing is that same value is being displayed again and again even on tilting the sensor,it only changes when the power is switched off and then again turned on and then the new value is being continuously displayed until it is again switched off and then turned on.

Parents
  • 0 in reply to Ash J

    #include "twi.h"

    sbit SDA = P1^7;
    sbit SCL = P1^5;

    void I2CInit(void)
{
        SDA = 1;
        SCL = 1;
}


void I2CStart(void)
{
        SDA = 1;    //Start condition
        SCL = 1;
        SDA = 0;
        SCL = 0;
}


void I2CRestart(void)
{
        SDA = 1;     //Transmit restart condition. I dont kno this is correct restart condition or not
        SCL = 1;
        SDA = 0;
        SCL = 0;
}


void I2CStop(void)
{
        SDA = 0;    //stop condition at the end of transmission
        SCL = 1;
        SDA = 1;
}


void I2CAck(void)
{
        SDA = 0;    //transmit ack
        SCL = 1;
        SCL = 0;
}


void I2CNak(void)
{
        SDA = 1;    //transmitt nack
        SCL = 1;
        SCL = 0;
}


unsigned char I2CSend(unsigned char Data)
{
        unsigned char i, ack_bit;

        for(i=0;i<8;i++)      //send data out on sda line with msb first
        {
                SCL = 0;
                if ((Data & 0x80) == 0)
                        SDA = 0;
                else
                        SDA = 1;

                SCL = 1;
                Data<<=1;
        }
        SCL = 0;
        SDA = 1;              //configure as input pin. doubtful
        SCL = 1;
        ack_bit = SDA;        //read ack bit
        SCL = 0;
        return !ack_bit;     //i m doubtful about this
}


unsigned char I2CRead(void)
{
        unsigned char i, Data=0;

        for(i=0;i<8;i++)
        {
                SDA = 1;         //read the 8bit data
                SCL = 0;
                SCL = 1;

                if(SDA)
                        Data |=1;
                if(i<7)
                        Data<<=1;
        }
        SCL = 0;
        SDA = 1;
        return Data;
}

    all the functions are named. so thought that comments may not be required.

Reply
  • 0 in reply to Ash J

    #include "twi.h"

    sbit SDA = P1^7;
    sbit SCL = P1^5;

    void I2CInit(void)
{
        SDA = 1;
        SCL = 1;
}


void I2CStart(void)
{
        SDA = 1;    //Start condition
        SCL = 1;
        SDA = 0;
        SCL = 0;
}


void I2CRestart(void)
{
        SDA = 1;     //Transmit restart condition. I dont kno this is correct restart condition or not
        SCL = 1;
        SDA = 0;
        SCL = 0;
}


void I2CStop(void)
{
        SDA = 0;    //stop condition at the end of transmission
        SCL = 1;
        SDA = 1;
}


void I2CAck(void)
{
        SDA = 0;    //transmit ack
        SCL = 1;
        SCL = 0;
}


void I2CNak(void)
{
        SDA = 1;    //transmitt nack
        SCL = 1;
        SCL = 0;
}


unsigned char I2CSend(unsigned char Data)
{
        unsigned char i, ack_bit;

        for(i=0;i<8;i++)      //send data out on sda line with msb first
        {
                SCL = 0;
                if ((Data & 0x80) == 0)
                        SDA = 0;
                else
                        SDA = 1;

                SCL = 1;
                Data<<=1;
        }
        SCL = 0;
        SDA = 1;              //configure as input pin. doubtful
        SCL = 1;
        ack_bit = SDA;        //read ack bit
        SCL = 0;
        return !ack_bit;     //i m doubtful about this
}


unsigned char I2CRead(void)
{
        unsigned char i, Data=0;

        for(i=0;i<8;i++)
        {
                SDA = 1;         //read the 8bit data
                SCL = 0;
                SCL = 1;

                if(SDA)
                        Data |=1;
                if(i<7)
                        Data<<=1;
        }
        SCL = 0;
        SDA = 1;
        return Data;
}

    all the functions are named. so thought that comments may not be required.

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