Question

I have to split a number into its digits in order to display it on an LCD. Right now I use the following method:

pos = 7;

do
{
    LCD_Display(pos, val % 10);
    val /= 10;
    pos--;
} while (pos >= 0 && val);

The problem with this method is that division and modulo operations are extremely slow on an MSP430 microcontroller. Is there any alternative to this method, something that either does not involve division or that reduces the number of operations?

A note: I can’t use any library functions, such as itoa. The libraries are big and the functions themselves are rather resource hungry (both in terms of number of cycles, and RAM usage).

Answer 1

You could do subtractions in a loop with predefined base 10 values.

My C is a bit rusty, but something like this:

int num[] = { 10000000,1000000,100000,10000,1000,100,10,1 };

for (pos = 0; pos < 8; pos++) {
  int cnt = 0;
  while (val >= num[pos]) {
    cnt++;
    val -= num[pos];
  }
  LCD_Display(pos, cnt);
}