The main purpose of developing this project is as follows:
- Implementing and development caculator with microcontroller 8051.
- Writing code in c language using Keil C51
- String handling in C51 for 8051
- Compiling and burning of program in microcontroller
- Real time Test of the project.
Interfacing Keypad with Microcontrollers:
Keypads are often used as a primary input device for embedded microcontrollers. The keypads actually consist of a number of switches, connected in a rows and columns arrangement as shown in Fig 1.
In order for the micro controller to scan the keypad, it outputs a nibble to force one (only one) of the columns low and then reads the rows to see if any buttons in that column have been pressed. The rows are pulled up by the internal weak pull-ups in the 8051 ports. Consequently, as long as no buttons are pressed, the micro controller sees a logic high on each of the pins attached to the keypad rows. The nibble driven onto the columns always contains only a single 0. The only way the micro controller can find a 0 on any row pin is for the keypad button to be pressed that connects the column set to 0 to a row. The controller knows which column is at a 0-level and which row reads 0, allowing it to determine which key is pressed. For the keypad, the pins from left to right are: R1, R2, R3, R4, C1, C2, C3, C4.
You will design a integer calculator with a keypad input. Your design should be able to read the operands (integers 0 to 9) and the operator from the keypad. You can design any combination of the input sequence as you like. For example, you may wish to input in the way:
1. pick the first operand
2. pick the operator
3. pick the second operand
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