I have a calculation which is the following:
1472 / 48 = 30.666667
(30 * 48) = 1440
(0.666667 * 48) = 32
So the numbers I nead are 1440 and 32, which can be calculated with the real part and the fractional part of the first calculation. Using the following piece of code I find the real part, but the fractional part is on a scale.
#define SHIFT_AMOUNT 16
// 2 bytes is used to map divisions
#define SCALE_FACTOR 65535 // (2^16)
#define SHIFT_MASK ((1 << SHIFT_AMOUNT) - 1)
uint32_t total_msgs = DATA_LENGTH << SHIFT_AMOUNT;
total_msgs /= PAYLOAD_SIZE;
uint8_t real_part = total_msgs >> SHIFT_AMOUNT; // 30
uint32_t decimal_part = total_msgs & SHIFT_MASK; // 43690
Now for the last calculation I'm stuck. How do I get 32 from 43690 (which really is ((43690 / 65535) = 0.666667) ?
The usual way to solve this problem is the % operator:
quotient = DATA_LENGTH / PAYLOAD_SIZE;
fraction = DATA_LENGTH % PAYLOAD_SIZE;