topic Re: MMA8451Q Data access using interrupt in Sensors

MMA8451Q Data access using interrupt

anhnguyen — Tue, 03 Feb 2026 21:12:10 GMT

Hi all, i'm using MMA8451Q.
I'm accessing data via hardware interrupt.
After i activate MMA8451Q , it asserts SRC_DRDY interrupt bit indicating the presence of new data and/or data overrun.

I have tried to clear this bit by reading the X, Y, and Z data as datasheet said (page 25).

But this bit has not been cleared.

Any body, please tell me what is wrong here and what should i do?

Thanks,

Re: MMA8451Q Data access using interrupt

TomasVaverka — Mon, 26 Nov 2012 14:08:49 GMT

Hi,

Please make sure you read out all the OUT_X_MSB, OUT_Y_MSB and OUT_Z_MSB registers. You can use either a single multiple-byte read operation or read out those registers using a single byte read as shown in the below simple examples.

Data_Ready = IIC_RegRead(MMA8451_IIC_ADDRESS, INT_SOURCE_REG);

if (Data_Ready & 0x01) //Is new set of data ready?

{

IIC_RegReadN(MMA8451_IIC_ADDRESS, OUT_X_MSB_REG, 6, &AccData[0]);

PTCD = PTCD ^ 0x01;

}

Data_Ready = IIC_RegRead(MMA8451_IIC_ADDRESS, INT_SOURCE_REG);

if (Data_Ready & 0x01) //Is new set of data ready?

{

IIC_RegRead(MMA8451_IIC_ADDRESS, OUT_X_MSB_REG );

IIC_RegRead(MMA8451_IIC_ADDRESS, OUT_Y_MSB_REG );

IIC_RegRead(MMA8451_IIC_ADDRESS, OUT_Z_MSB_REG );

PTCD = PTCD ^ 0x01;

}

I toggled the PTC0 pin to monitor the SRC_DRDY bit on my o-scope.

Hopefully this makes sense, but let me know if the problem continues.

Regards,

Tomas

Re: MMA8451Q Data access using interrupt

bergo — Sun, 26 May 2013 14:27:29 GMT

I'm wondering,

what is the PTC0 pin?

Re: MMA8451Q Data access using interrupt

TomasVaverka — Mon, 27 May 2013 11:05:45 GMT

Hi Bergo,

I have used this pin just to monitor the SRC_DRDY bit, it does not have any connection with the previous instructions that are necessary to deassert the interrupt. You can ignore this line of the code - PTCD = PTCD ^ 0x01

Regards,

Tomas