<WRAP centeralign round box>
<WRAP><color red><fs 200%>Corning Community College</fs></color></WRAP>
<WRAP><fs 150%>ENGR1050 C for Engineers</fs></WRAP>
</WRAP>

======Project: ELECTRONICS PI FUN - LEDBAR BINARY COUNTER (epf1)======

=====Objective=====
To adapt your bcf0 program to, instead of displaying values to STDOUT, instead lights up LEDs on the LEDbar, so the binary counter, in incrementing or decrementing fashion, is better visualized.

=====Reading=====
In "The C Book", please read through Chapter 5.

=====Diagram=====

To refresh your memory, here is a diagram of the circuit you can build to drive the LEDbar:

{{:haas:fall2019:c4eng:projects:ledbar.png?400|}}

Be sure to use 220 Ohm resistors for this.

=====Program=====
It is your task to adapt your bcf0 program so that, upon accepting various pieces of input from the user, acts as a binary counter, lighting up the resultant LEDs in binary (1 being on, 0 being off), inserting an adequate delay so we can watch as it proceeds from a starting to an ending value.

=====Specifications=====
Your program should:

  * have valid, descriptive variable names of length //no shorter than// 4 symbols
  * have consistent, well-defined indentation (no less than 4 spaces per level of indentation)
    * all code within the same scope aligned to its indentation level
  * have proximal comments explaining your rationale and what is going on, throughout your code
  * to STDERR, prompt for the starting value (0-1023)
    * properly store this in a variable of type **signed short int**
  * to STDERR, prompt for the ending value (0-1023)
    * properly store this in a variable of type **signed short int**
  * immediately after each input, check to make sure starting and ending values fall appropriately in the range stated; if in violation, display an error (to STDERR) and exit with a non-zero value.
  * check the starting and ending values to determine if we are to perform an incrementation or a decrementation.
  * in binary, display the starting number and all the others as well to the LEDs
  * proceed to the next value in sequence, doing the same
  * keep going until you have arrived at the ending value, visualizing it on the LEDs it as well
  * using a single return statement at the conclusion of the code, return a 0 indicating successful operation
  * if you do not have an LEDbar component (or a fully working LEDbar component), substitute as appropriate with individual LEDs (don't forget the resistors!)

Some additional points of consideration:
  * Note that the driving variables in your loops need to be at least of type **short int**, otherwise you may get a warning when you compile it.

=====Execution=====

====Sample incrementation run====
<cli>
pi@raspberrypi:~/src/c4eng/epf1$ ./epf1
Enter starting value (0-1023): 12
Enter ending value (0-1023): 28
pi@raspberrypi:~/src/c4eng/epf1$ 
</cli>

The execution of the program is short and simple- obtain the input, do the processing, produce the output, and then terminate.

====Sample decrementation run====
<cli>
pi@raspberrypi:~/src/c4eng/epf1$ ./epf1
Enter starting value (0-1023): 17
Enter ending value (0-1023): 0
pi@raspberrypi:~/src/c4eng/epf1$ 
</cli>

====Sample run with invalid input given (scenario 1)====
<cli>
lab46:~/src/c4eng/epf1$ ./epf1
Enter starting value (0-1023): 5543
ERROR: input value must be between 0-1023!
lab46:~/src/c4eng/epf1$ 
</cli>

====Sample run with invalid input given (scenario 2)====
<cli>
lab46:~/src/c4eng/epf1$ ./epf1
Enter starting value (0-1023): 255
Enter ending value (0-1023): 7168
ERROR: input value must be between 0-1023!
lab46:~/src/c4eng/epf1$ 
</cli>

=====Obtaining binary values=====
You might wonder how, when you are limited to non-binary input, how you can obtain the binary value so that you can work with it.

There are a couple ways to go about this:

====Method one: convert from decimal to binary====
Using the division method, you can convert a decimal value to binary, continually dividing the value (or its quotient) by the base, until the quotient is 0, then we use the remainders to give us the binary value:

  * value / base
  * value = 15
  * value / 2
    * ie: 15 / 2
      * quotient: 7
      * remainder: 1
  * value = quotient
  * value / 2
    * ie: 7 / 2
      * quotient: 3
      * remainder: 1
  * value = quotient
  * value / 2
    * ie: 3 / 2
      * quotient: 1
      * remainder: 1
  * value = quotient
  * value / 2
    * ie: 1 / 2
      * quotient: 0
      * remainder: 1

The binary for 15 (decimal) is 1111 (binary)

Or:
  * value = 11
  * value / 2
    * quotient: 5
    * remainder: 1
  * value = 5
  * value / 2
    * quotient: 2
    * remainder: 1
  * value = 2
  * value / 2
    * quotient: 1
    * remainder: 0
  * value = 1
  * value / 2
    * quotient: 0
    * remainder: 1

The binary for 11 (decimal) is 1011 (binary).

NOTE that the order in which we get the remainders produces the number from right to left.

====Method 2: bitwise AND the place values====
If one understands the weight values corresponding with the places of each bit in a binary number, we can simply do a bitwise AND and see if the result is greater than 0 or not:

^  2 to the 7  ^  2 to the 6  ^  2 to the 5  ^  2 to the 4  ^  2 to the 3  ^  2 to the 2  ^  2 to the 1  ^  2 to the 0  ^
|  128  |  64  |  32  |  16  |  8  |  4  |  2  |  1  |

So, if we wanted to see if the 2 to the 7th bit is active, we can simply:

<code c>
    value  = number & 128;
</code>

We can then check of value is greater than 0; if it is, we've got a 1 in that position, if it isn't, we have a 0.

We can then repeat the operation for 64, 32, 16, etc. down to 1, to get each bit of our number.

NOTE that I have only taken us out to 8-bits. You may need to extend this to incorporate all the allowed values for this project.

=====Submission=====
To successfully complete this project, the following criteria must be met:

  * Code must compile cleanly (no warnings or errors)
  * Output must be correct, and match the form given in the sample output above.
  * Code must be nicely and consistently indented
  * Code must be well commented
  * Do NOT double space your code. Group like statements together.
  * Output Formatting (including spacing) of program must conform to the provided output (see above).
  * Track/version the source code in a repository
  * Submit a copy of your source code to me using the **submit** tool.

To submit this program to me using the **submit** tool, run the following command at your lab46 prompt:

<cli>
$ submit c4eng epf1 epf1.c
Submitting c4eng project "epf1":
    -> epf1.c(OK)

SUCCESSFULLY SUBMITTED
</cli>

You should get some sort of confirmation indicating successful submission if all went according to plan. If not, check for typos and or locational mismatches.