mmcd/PocketLogger accuracy... strange

[calan]

I was playing around and just for giggles decided to switch from mmcd to PL while running some high temps the other night. MMCd was showing from around 216* to 223*, and PL was showing about 10 degrees cooler on average.

Any idea why they would be different, and which one is more accurate?

And if the coolant temps are this inaccurate with one of them, what else is out in left field?

[steve]

Which version of MMCd?

[calan]

Hey Steve... 1.8g I believe. The latest I've found.

[steve]

I remembered that there was a change to the coolant interpolation tables but after checking I see that it was way back in 1.3b. MMCd should be producing the same values as DSMLink. Pocketlogger might produce the numbers as from the original TMO logger.
Unless you have a MUT or measure the actual coolant temp it will be hard to say who's correct.

[calan]

Well... bummer... not sure which to believe.

Must be a problem with one of the transfer functions I guess?

[hakcenter]

// Coolant temperature, degrees C
// interp - 80
static UInt8 s_coolant[17] = {
        0xEE, 0xBE, 0xA0, 0x90, 0x84, 0x7B, 0x73, 0x6C,
        0x65, 0x5F, 0x58, 0x51, 0x49, 0x40, 0x33, 0x15,
        0x15
    };
static void s_CoolantFetch(LoggerIndex idx, UInt8 byte, UInt8* nVal, UInt16* aVal, Char* text)
{

    UInt16 index = byte >> 4;
    UInt16 frac  = byte & 0xf;

    Int32 degC = (Int32)s_coolant[index]
                 + (Int32)frac * (Int32)(s_coolant[index+1] - s_coolant[index]) /16
                 - 80;

    Int16 degF = (Int16)((9 * degC / 5) + 32);

    if (nVal)
        *nVal = (UInt8)degF;
    if (aVal)
        *aVal = degF;
    if (text)
        StrPrintF(text, "%d %s", degF, loggerIndexUnits[idx]);
}

Theres the lookup code from pocketdyno, which matches mmcd output. My vote is on mmcd being more accurate.