float from two int16's

[Will Reeve]

I've got to fix something blind without the hardware (always a pain!). Anyway it comes down to needing a float instead of a int32.

rough code:
int16 a;
int16 b;
float c;

c = a / b;

[Charlie U]

Will,

You could try your tests with a quick and dirty program on the simulator in MPLAB to confirm your results.

If you can't do that, I would definitely cast the variables before the divide. Look at one example: if a < b then the divide using ints should yield 0, while the divide with floats should yield a number between 1 and 0 in floating point notation.

[Will Reeve]

I wondered if some automatic casting would happen? I know CCS has some strange rules with casts. I haven't used a float for several years!

[Charlie U]

Don't get your hopes up. I have learned the hard way that I should always make an explicit cast when I want thing to work out correctly. Don't rely on automatic/assumed casting.

In the case that you have mentioned, I just ran it on the simulator, and without the cast, the division is performed as int16 first, then the result is cast to a float. So, 2/4 = 0.00. If you cast both a and b to float, then divide, the result is 0.500. I tried this with a few values and the result is the same, int16 division then cast.

So, in your case, since you need to make the change "blind" and need the highest probability of success, cast first, then divide.

[Will Reeve]

Thanks. I really should install MPLAB again. When I switched to the CCS IDE I never went back. MPLAB never got installed on my new PC.

[SherpaDoug]