CODEWITHSUNDEEP
cavrtype-conversionarduino-uno
Joshua LI
Joshua LI

Reputation: 4733

Unexpected float to unsigned char conversion in AVR programming

Microcontroller : ATmega328P in Arduino Uno
Clock Frequency : 16MHz

void timeDelay_CTC(float sec, unsigned char times)
{
    unsigned char cycles = (unsigned char)(sec / 0.000064f);
    OCR1A = cycles - 1;
    TCCR1A = 0b00000000;
    TCCR1B = 0b00001101;
    for( unsigned char i = 1; i <= times; i++ )
    {
        while( (TIFR1 & (1<<OCF1A)) == 0 ); 
        TIFR1 |= (1<<OCF1A);
    }
    TCCR1A = 0;
    TCCR1B = 0;
}

The function is used for calculating the number of time delay cycles and then implement it.

int main(void)
{
    //Initialization
    LED1_DDR |= (1<<LED1_BIT);
    LED1_PORT |= (1<<LED1_BIT);

    //Start
    while(1)
    {
        LED1_PORT ^= (1<<LED1_BIT);
        timeDelay_CTC(1, 1);
    }
}

However, when running the code above, the LED light does not toggle. If I just type OCR1A = 15624; (the number of cycles for 1s), it works well. Therefore, the problem should come from the calculation of unsigned char cycles = (unsigned char)(sec / 0.000064f); I think that the data type conversion may be wrong. Can you teach me how to make it work? Or give me some hints.

Upvotes: 0

Views: 262

Answers (1)

Saking
Saking

Reputation: 100

Please check the range of unsigned char, it is [0 255], it is not big enough for your application. Try to use unsigned int.

Upvotes: 3

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