Curing my newbness

Forum 2005-2010 (read only) Software Syntax & Programs
1

I can't figure out how to break a multi-digit number into single digit ones. I have googled it, and other people have had the same question, but the answers include functions and symbols that I am not familiar with. If someone could break it down into baby language for me, I would be most appreciative.

Here is the code that supposedly does it:

#define NUM_DIGITS 4

// table of 7-segment patterns
const byte seg_def[] = // segment patterns for digits 0-9
{//GFEDCBA
B0111111, // '0'
B0000110, // '1'
B1011011, // '2'
B1001111, // '3'
B1100110, // '4'
B1101101, // '5'
B1111101, // '6'
B0000111, // '7'
B1111111, // '8'
B1100111 // '9'
};

byte digit_array[NUM_DIGITS];

void NumberToArray(word number)
{
char i;

// initialize all digits to the empty pattern (no segments lit)
for (i=0;i<NUM_DIGITS;i++) digit_array*=0;*

  • // extract each digit (right to left)*
  • for (i=NUM_DIGITS-1;i>=0;i--) {*
  • // extract least significant digit as an index into the*
  • // segment pattern table*
    digit_array*=seg_def[number%10];
    Serial.println(seg_def[number%10]);
    _     // get next digit*_
    * number=number/10;*
    * // exit if there are no more digits to avoid leading zeroes*
    * if (number==0) break;*
    _ }/for/
    }/NumberToArray/_
    What is a char? Why not use int i instead of char i?
    How do you use bytes? I understand what they are, but how would you call them to light certain segments of a 7-segment led?
    What is the %?
    I am trying to break down a multi-digit integer and seperate it into single-digit integers. I understand there are multiple ways to do this, but I don't understand the functions used to do it. Is there an index of commands that I can use to look up the correct usage of these functions I don't understand? Anyway, any help would be stellar.
2

Is there an index of commands that I can use to look up the correct usage of these functions I don't understand?

Yeah, it's called google.

The two usual ways to convert a number into a string are sprintf and itoa.

int someNum = 259;
char numAsStg[10];

atoi(someNum, numAsStg, 10);

or

sprintf(numAsStg, "%d", someNum);

3

...under the tab reference at arduino.cc there is an index of commands. Wow.

4

There is, but it is by no means an exhaustive list of functions that can be used on the Arduino. Not by long ways.

5

There was another post that said the sprintf function wasn't a good one to use because it could cause buffer overflow errors. And I believe I read that strings in general are more burdensome than integers, etc. Also, the problem with atoi is, if I understand this C string handling - Wikipedia correctly, is it can't distinguish between a true zero and a blank character. The code that I submitted is supposed to not turn a multi-digit number into a string at all.

6

electrosheep:

Have you forgotten how base-10 works? I am beginning to wonder if we need a tutorial (facepalm) on how base-10 works, because this question comes up on a regular basis, it seems...

Lets say you have a number: int num = 2957;

You want the '2', '9', '5', and '7' separate...

Divide it by 1000: int num1 = num / 1000;

Since num and num1 are integer variables, num1 will be "2" - there's your first number.

Multiply that by 1000: int temp = num1 * 1000;

Subtract the result (2000) from your original number: num = num - temp;

The variable num is now "957".

I'll leave it to you as to how to get the rest, but realize you have a "hundred's place", a "ten's place", and a "one's place"...

/I feel like I am in grade school...

7

Perfect. I appreciate the response. I thought I remembered integers being rounded. I didn't see any threads that particularly made sense to me, but my discovery of the reference tab has helped me. I think there should be more tutorials outlining basic C++ principles. Perhaps one day, when I am more experienced, I'll make some.