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Digital Logic Calculator Providing Calculations for Use with Microcontrollers Collin Butler John Reece EGGN383 Overview Objective: create a calculator to perform common calculations for typical microcontroller use Design Goals: – Calculations for 16-bit systems – Simple arithmetic operations – Conversions to binary and hexadecimal Hardware MC9S12C32 Microcontroller HD44780U LCD Sparkfun COM-08653 Keypad Pushbuttons (x4) Schematic Operation Arithmetic Operations – Enter the first number – Press desired operator button – Enter the second number – Press any operator button to display result Base Conversions – Enter the number – Press desired operator (binary, hex) – Result displayed automatically Software CodeWarrior IDE – Initialization of LCD – Input of numbers read from the keypad – Arithmetic calculations and base conversions – Display of input and output numbers on LCD Flowchart Initialization • I/O Ports • Port T • DDRT = 0x3f for LCD use • Port AD • DDRAD = 0x15 • • Defines direction of digital I/O on port AD ATDDIEN = 0x6a • Additional definition needed for inputs on Port AD • Port M • All high impedance inputs Number Input • Waits for a user input • Keypad or operation • Uses getkey() function for keypad input • Replaced PTT with PTAD Digital I/O register for Port AD • Key strokes are placed in an array a[i] Number input (continued) • However, numbers input need to be placed in a variable with the correct value • Example: If the user was to input a 1, 2, and 7: a[] = [1, 2, 7, 0 . . . 0], i=3 We would desire the value of our variable to be 127. • Need code to implement: “one” = a[i-1]*(10^0) + a[i-2]*(10^1) +….+a[0]*(10^i) Number input (continued) • Accomplished by using: • Note: • Loop counter i is incremented during the number input loop, thus if 3 numbers were entered, i=3 Operations • Addition (0x2b, ‘+’), subtraction (0x2d, ‘-’), multiplication (0x2a, ‘*’), and division (0x2f, ‘/’) • Push buttons read from PTM pins going high • To binary (0x62, ‘b’), To hex (0x78, ‘x’) • On keypad, buttons * and # • This skips the entry of a second number • ASCII value is assigned to char variable “op” Operations (continued) • Once variables “one” and “two” have been entered, they are operated on accordingly • Operations done according to value assigned to the op variable • Results are placed in the integer variable “result” Binary and Hex Conversions For Binary: log[ ] = {32768, 16384, 8192, 4096, 2048, 1024, 512, 256, 128, 64, 32, 16, 8, 4, 2, 1} For Hex: log[ ] = {4096, 256, 16, 1} Possible Improvements Provide option for logic operations (AND, OR, XOR, NOT) Implement keypad with a larger quantity of buttons for additional operations Equals button Memory of previous answers Questions?