从函数返回指针读取值

Question

I am developing a code in which I need to read the value of function which returns value in pointer.

below is the function whose value needs to be read (*ip)

int16_t getLastValueFromADC()
{
    volatile uint16_t *ip;

    ip  = GET_FPGA_REGISTER_ADDRESS(REG_CURRENT_ADC_SAMPLE_R);

#ifdef _JSB_BEHAVIOUR_0_65536
    if (tighteningDirectionCCW)
    {
        tempValue = (int16_t)(*ip);
        tempValue = (OFFSET_BB2AD - tempValue);
    }
    else
    {
        tempValue = ((*ip) + OFFSET_BB2AD);
    }
    return ((uint16_t)tempValue);
#endif
    return *ip;
}

I am reading the value using below code:

int16_t vref2v5 = getLastValueFromADC();             
printf("VREF2V5 Status for Torque signal:  %d\n",vref2v5);

not getting expected values it is showing some negative value number.

Please suggest

Thanks & Regards

Answer 1

The return type of the function is a 16 bit integer,

int16_t getLastValueFromADC();

However the variable used to represent the result to be returned by the function is an unsigned integer.

volatile uint16_t *ip;

Unsigned integers are meant to be parsed by the compiler in such a way that there value is always positive. This is not the case with regular(signed) integers, in which case the MSB(most significant bit; leftmost bit) determines whether the value should be treated as postive(0) or negative(1).