Thread: splitting integer into digits for PIC microcontroller -- newbe with C++

Hello,

I'm new to C++. Years ago I dabbled in assembly lanquage as a hobby, but I never really got deep into manipulating numbers with it, so now that I'm learning C++, primarily for the purpose of microcontroller programming, I need to learn it.

I'm working on a digital display circuit which will use multiple PIC microcontrollers. I need to be able to separate an integer into its digits for the ability to display them. Can someone help me here?

The main PIC will sent the integer, but I need the controllers that are doing the actual 7 segment output to sepearate their appropriate numbers (for example, one PIC will be handling the ones and tens, and the second will be handling the hundreds and thousands). For reasons I won't get deep into right now, I am not using a single chip to multiplex the display.

If someone can show me how to do this, and explain it a little, Im sure I will catch on.

Thanks in advance!

I know a poor implementation of a brute force method which involves just diving by 10 a bunch and subtracting from your target integer but I know someone on this board posted a better implementation.

Would either of you care to elaborate?

Code:

right_digit = number%10;
rest_of_it = number/10;

In a loop, naturally.

OK, I was just reading up on the modulus operator, and it makes sense now. I wasn't familiar with it.

So, in my project, I will have 2 PIC microcontrollers each handling 2 digits of a display.
The one handling the thousands and hundreds, for example, will have the following

Code:

thousands_digit=num/1000
remainder=num%1000
hundreds_digit=num/1000

Does that look right?

Oops, what I actually meant was

Code:

thousands_digit=num/1000
remainder=num%1000
hundreds_digit=remainder/100

In your example, it should give me the hundreds_digit of 3, (with a remainder of 56 if I added the modulus to remainder)

Correct?

Rather than asking, have you tried actually writing the code in a standard C++ compiler and testing it yourself?

When I develop code for microcontrollers, it's not usual for me to test logic bits like this on a standard C compiler and see the results on the console before moving the code to the embedded source code.

I am actually just getting into this, and I've had a problem getting my IDE setup correctly, so I haven't been able to run the simulator.
During the day, I'm at work and don't have access, so when I'm dabbling with ideas, the only thing for me to do is research it.
I will definitely be simulating long before I write it to the chip.

Thanks though.

Maybe I'm misunderstanding the modulus operator. I thought the modulus operator gives you the remainder after dividing by the applied number.

Code:

num = 8765
Remainder = num %1000

Would assign the value of 765 to Remainder, where as

Code:

Thousands_digit = num / 1000

would assign the value ot 8 to Thousands_digit.

Yes, you're right. If you have a C compiler that doesn't treat integer divisions that way, what you actually have is a "C Compiler" in that it is something that claims to be a C compiler but isn't. The C language requires that (eg) 8765 / 1000 must give 8.

EDIT: Forgot we were in the C++ forum. The same is true of the C++ language.

Originally Posted by grumpy

In C89, division by zero involving negative operands did not necessarily have a specified result.

I'm assuming the "by zero" in there is spurious?

But in either standard, int / int was going to be an int and never a float.