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Embedded and Microcontrollers
Blog division operation with float variable mplabx v6.00 xc16 (v2.00)
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  • Author Author: hazard
  • Date Created: 18 May 2024 10:55 AM Date Created
  • Views 1115 views
  • Likes 3 likes
  • Comments 10 comments
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division operation with float variable mplabx v6.00 xc16 (v2.00)

hazard
hazard
18 May 2024

hi every one.

I have some problem trying make some division with float variable.

some one can help me please.

main.c

while(0)
{
    menu_state = PARAM_MENU;
    param_menu = PARAM_MENU_FREQ;
    pwmq_freq_ui16 = encoder_knob_read();
    set_PWM1_FREQ();
    //set_PWM1_DT();
    sprintf(buffer1,"2-FREQ:%5uHz",pwmq_freq_ui16);
    oled_setcursor(0,2);
    oled_print_string(buffer1);
    
    return 0;
    }
    
    
    // prototype function
    
    void set_PWM1_FREQ(void)
{
    PWM1_set_Freq(pwmq_freq_ui16);  
}

pwm.c file

void PWM1_set_Freq(uint16_t Freq_PWM1)
{
     float Freq_PWM1_F = (float)1/Freq_PWM1;

    
    //uint16_t new_valor = (uint16_t)((65535*Freq_PWM1_F))/PWM1_CONST_2;
//    
//    if(OC1RS != new_valor)
//    {
//        OC1RS = (uint16_t)new_valor;
//    }
}

if I do this        float Freq_PWM1_F = (float)1/;

I get a:

image

in this moment  ( break point on main.c in line 8     "set_PWM1_FREQ();" )

image

when I step the line 44 the watches editor clear all the value.

but if I try do this:

pwm.c

void PWM1_set_Freq(uint16_t Freq_PWM1)
{

    float Freq_PWM1_F = (float)1/1000;

    
    //uint16_t new_valor = (uint16_t)((65535*Freq_PWM1_F))/PWM1_CONST_2;
//    
//    if(OC1RS != new_valor)
//    {
//        OC1RS = (uint16_t)new_valor;
//    }
}

works fine.

image

I know is confused my discription.

but if some one can try read and help I will aprecciate the kindness.

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  • genebren
    genebren over 1 year ago

    You need to declare Freq_PWM1_F outside of the function.  If it is inside a function (as it is now) it is declared on the stack frame, which is not guaranteed to be available after the function call.  I am a little confused to how this was allowed to compile without an error.   

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  • hazard
    hazard over 1 year ago in reply to genebren

    I hane tryid declare a global variable but the same hapen.

    I think I solve this with:

    double PER_PWM1_F = (double)1/(double)Freq_PWM1;

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  • hazard
    hazard over 1 year ago in reply to genebren

    I hane tryid declare a global variable but the same hapen.

    I think I solve this with:

    double PER_PWM1_F = (double)1/(double)Freq_PWM1;

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