| ??? 01/27/08 15:24 Read: times |
#149980 - I'd like to disagree Responding to: ???'s previous message |
Esko Ilola said:
The root cause was the compiler assumptions over the constants. These are always treated as SIGNED integers if not told othervise. This also applies for intermediate calculation results as in that comparison.
with this statement of yours. I think that the compiler has seen the statement as an uint16*uint16 and has not promoted the integer result to 32 bit. So, it does a 16 bit compare; which is correct. So, the following syntax would make it to work as expected. ...
if ( MAX_POWER_LOSS < (uint32_t)Current_meas * (Prereg_meas - Voltage_meas) ) {
pwmvalue += (uint16_t)(Voltage_set + Voltage_off);
}
...
Here I am assuming that Prereg_meas is again uint16; need not be, but the result is uint16. The typecast for Current_meas makes sure that there is a 32 bit multiply yielding a 32 bit result for the compiler to use in the compare operation. Similarly, when the compiler sees the typecast for Current_meas here, it should perform a 32 bit division. ...
pwmvalue = MAX_POWER_LOSS / (uint32_t)Current_meas;
...
Esko Ilola said:
This, of course, is highly compiler dependent issue.
I agree with this statement. My ass is still sorry but it is saved ;) Ass sorry but ass happy. That's what matters. ;) I'm sure your post will save some more sorry esses. Cheers Jerson |
| Topic | Author | Date |
| The art of typecasting | 01/01/70 00:00 | |
| I'd like to disagree | 01/01/70 00:00 | |
| two comments | 01/01/70 00:00 | |
| Two comments on comments | 01/01/70 00:00 | |
| The Art of correct Constants | 01/01/70 00:00 | |
| int - number of bits unknown | 01/01/70 00:00 | |
| Corrected Art of correct Constants | 01/01/70 00:00 | |
| More assumptions | 01/01/70 00:00 | |
| stdint.h | 01/01/70 00:00 | |
| Or, in the absence of stdint.h... | 01/01/70 00:00 | |
| Const vs #define | 01/01/70 00:00 | |
| Opps! | 01/01/70 00:00 | |
| which may be a reason to prefer #define over const | 01/01/70 00:00 | |
| enum | 01/01/70 00:00 | |
| Varies | 01/01/70 00:00 | |
| Know Thy Stuff - enum | 01/01/70 00:00 | |
| You are right | 01/01/70 00:00 | |
| Know Thy Stuff | 01/01/70 00:00 | |
| And... | 01/01/70 00:00 | |
| I'll pass(cal) on that one :) | 01/01/70 00:00 | |
| Everything in C defaults to int, which is signed | 01/01/70 00:00 | |
| Never overlook lint | 01/01/70 00:00 | |
| before Steve says it... | 01/01/70 00:00 | |
| Pascal | 01/01/70 00:00 | |
| strong typing | 01/01/70 00:00 | |
| why Ada never took off | 01/01/70 00:00 | |
| Wirth-less | 01/01/70 00:00 | |
Why ? | 01/01/70 00:00 |