[ARM] Reading Negative Values of accelerometer

[nsparag]

Hello
Im interfacing accelerometer with TivaC and displaying the RAW data on UART.

void main(){

signed int accelerationX;

accelerationX = getAcceleration_X();
if (accelerationX>=0){
UART_OutString("\r\nX Axl: ");
UART_OutUDec((unsigned short) accelerationX);
} else {
UART_OutString("\r\nX Axl: - ");
UART_OutUDec((unsigned short) (accelerationX*-1));
}

}

Such type of code I got on some forum.
I'm not understanding why " accelerationX*-1 " is done when acceleration is negative.

 

[BradtheRad]

It appears that the value is stored in a unsigned variable which only holds positive numbers. Therefore a negative value needs to be multiplied by -1.

This has the result of storing the absolute value of acceleration.

 

[Duresh]

I think

UART_OutUDec((unsigned short) (accelerationX*-1));

has no meaning. It is multiplied by -1 and again cast into "unsigned".

And other thing is

accelerationX;

is "int". But it is casted into "short". I guess output of

getAcceleration_X()

is short.