TMP1075: Temperature Conversion

Hi Kaushal,

Please check out this example code from Sysconfig.

dev.ti.com/.../index.html

/*
 *  ======== TMP1075_toIntCelsius ========
 *  Convert raw temperature register value to degrees Celsius rounded to the
 *  nearest integer
 */
int32_t TMP1075_toIntCelsius(int32_t x)
{
    /* Shift raw register value to form a proper Q4 value */
    x >>= 4;

    /* Optional: Add bias to round before the final truncation */
    x += (x >= 0) ? (1 << 3) : -(1 << 3);

    /* Convert Q4 value to whole number */
    x /= 1 << 4; /* use division so small negative values round to 0 */

    return x;
}

/*
 *  ======== TMP1075_toMilliCelsius ========
 *  Convert raw temperature register value to milli-degrees Celsius
 */
int32_t TMP1075_toMilliCelsius(int32_t x)
{
    /* Shift raw register value to form a proper Q4 value */
    x >>= 4;

    /* Scale to milli-degrees, convert Q4 value to a whole number */
    return ((1000 * x) >> 4);
}

/*
 *  ======== TMP1075_toFloatCelsius ========
 *  Convert raw temperature register value to degrees Celsius
 */
float TMP1075_toFloatCelsius(int32_t x)
{
    /* Shift raw register value to form a proper Q4 value */
    x >>= 4;

    /* Convert Q4 value to a float */
    return ((float)x * 0.0625f);
}

Note that the two 8 bit bytes received from TMP1075 were combined into a 16bit signed value (stored in a 32 bit space for code portability) prior to being passed to the above functions. In the case of TMP1075, the high byte can be viewed as signed 8 bit integer temperature without further conversion.

    /* Sign extend and combine MSB with LSB */
    tmp = (((int32_t)(int8_t)rxBuf[0]) << 8) | rxBuf[1];

thanks,

ren