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FPU problem

Mehran Msba

When I enable FPU in compiler option,My equation result is wrong. 0 + 0 = 0 but I see -107374176 ! (byte view: 0xCCCCCCCC)

Code:

typedef struct
{
uint16_t year;
uint8_t  tA;
uint8_t  tB;
uint8_t  tc;
float    fl1;
float    fl2;
}mStruct;

in my function:
{
mStruct g1,g2;
.
.
myload(&g1);
.
g.fl1+= g.fl1 + paramIn;

.
.
.
}

RTOS is used too(RTX with cmsis_os).
Everything is OK without FPU option.

What is wrong?

Thanks.

Parents
  • 0 in reply to edPer Westermark

    sorry.

    myload function load last saved value from eeprom and I set fl1 member to zero for testing in this function.

    Its my goal:

    g.fl1 = g.fl1 + g.fl1 + paramIn;
or
g.fl1=2*g.fl1 + paramIn ;

    g.fl1 is zero when myload function executed. pramIn is zero too(passed parameter to this function.)

    result must be zero in this condition but I see that negative large number when fpu is enable.

    Thanks again.

Reply
  • 0 in reply to edPer Westermark

    sorry.

    myload function load last saved value from eeprom and I set fl1 member to zero for testing in this function.

    Its my goal:

    g.fl1 = g.fl1 + g.fl1 + paramIn;
or
g.fl1=2*g.fl1 + paramIn ;

    g.fl1 is zero when myload function executed. pramIn is zero too(passed parameter to this function.)

    result must be zero in this condition but I see that negative large number when fpu is enable.

    Thanks again.

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