Firstly we will make a simple calculator that
does simple operations like addition, subtraction, multiplication and
division. We have used the A, B, C, D keys for the above operations
respectively. For the 'equal to' operation we have used '#' key and for
'clear the screen' we have used '*' key in the keypad. In the attached
image, connections for keypad are mentioned.
For the coding part we have taken help from the already build code at the arduino site-
Rest is just tweaking it to run by changing the pins etc. We have modified the code for 1.8" TFT (ST7735R).
But this was very simple!! Lets go ahead
For both our input numbers the algorithm is basically the same.
Let the first number be a double named 'first'. We initialize it to be zero.
make a Boolean 'isDecimal' and initialize it as false. This means that
unless the decimal point is given as an input, the number is not a
Last, declare a float 'decimals' and set it as 10.0. We will use it for keeping a counter of our place after the decimal point.
if isDecimal is false, it means the number is not yet a decimal.
Suppose you are storing your input number from the keypad as key.
You just need to update first=first*10+key.
But if isDecimal is true, the number is a decimal. You need to now update as
first=first+key/decimals, and decimals=decimals*10.
keep repeating the above steps until the input for some operation is
detected. Then we similarly detect the second number. Using the
knowledge of the operation called, we operate the numbers and print the
result when '=' is detected.
Remember to restate the values of decimals=10.0 and isDecimal=false after detection for a number is complete.
case'0' ... '9': // This keeps collecting the first value until a operator is pressed "+-"if (isDecimal1==false)
first = first * 10 + (customKey - '0');
first=first+(customKey - '0')/decimals1;
Now, we have to add more buttons for the
scientific functionality. We have used some colorful buttons as shown in
figure. Now assign them accordingly. Take care to assign similar
buttons to similar functions.
Since evive uses Arduino Mega, we have used following pins: