Lab 1: Introduction to the 68HC12 - The Magic 8 Ball
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1. g a random number between 3 and 7 The program should have a menu that allows the user to select which type of answer will be generated After the answer is displayed the program should return to the menu It is not necessary to clear the screen when returning to the menu The answers that are generated are to be determined randomly The section below provides a suggestion for developing random values In order to earn full credit on the project the answers must be generated randomly The code must be logically written and well commented This is very important since you will be using this code as the basis of Labs 2 and 3 After being signed off by the TA you will turn in your flowchart from the prelab and the fully commented copy of your code Helpful Hints Here are several suggestions to get you started on the project 1 Start small Break the project up into several functions and begin by only debugging one at a time 2 Remember all Debug 12 functions must be prefaced by DB12 gt 3 Remember your main function must be called __main 4 Random number generation The free running counter _H12TCNT is a good source of random numbers This has a value from 0000 to OXxFFFF There are several different ways this can be used How you use it is up to you 5 To avoid possible compiler errors functions and function prototypes should use void for the variables to be passed2. 1 to each row and look for the 1111 value you see 1111 and the low bits of the key that was pressed was leftmost column containing the Port J le that is included in your header The value of Port t J to all low outpu used for output L be used to pass the value of the key back the key should be stored in this to read it ts although only the high nibble is to be released 7 Clear the Key Wakeup Flags by writing a 1 to the bit in the flag register Good programn KWIFJ that corresponds ning practice would not to the interrupt you just processed automatically set all the bits since later revisions of the program may use other interrupts that may happen simultaneously bu should only clear the bit of the be processed by other ISR ISRs A particular it specifically handles interrupt 6 Helpful Hints 1 You must use port J 2 Remember to assign the vector for the Key Wakeup using DB12 gt SetUserVector 3 Remember to clear the flag for the Key Wakeup hardware 4 You must include HC812A4 H in the header file If you do not include this then the compiler will not recognize any of the register names for the 6812 registers You must include DBUG12 H if you want to use any of the dbugl2 functions 5 Be sure to enable the pull ups AFTER you speci
3. MP S Magic 8 Ball Lab Exercises Magic Eight Ball 1 2 amp 3 Student s name amp ID Partner s name amp ID Your Section number TA s name Notes You must work on this assignment with your partner Hand in a printer copy of your software listings for the team Hand in a neat copy of your circuit schematics for the team These will be returned to you so that they may be used for reference 1 POINTS TA init 2 POINTS TA init 3 POINTS TA init Grade for performance verification 50 max Grade for answers to TA s questions 20 max Grade for documentation and appearance 30 max Grader s signature Date MPS ECSE 4790 Microprocessor Systems Lab 1 Introduction to the 68HC12 The Magic 8 Ball Overview The 68HC12 is a 16 bit microprocessor that is the follow on to the 6811 that was used in COCO The 6812 is far more powerful than the 6811 It provides more support of interrupts full 16 bit addressing and several new features not found on the 6811 The objective of this lab is to introduce you to programming the 6812 using C This will be done by writing a small program which will be modified in later labs and used as the basis of a larger project For this lab you will create a small program that is used to generate answers to questions The user will be able to input information via the terminal keyboard and the answers will be
4. and the return type if there is nothing being passed to the function or returned by the function Lab 2 Interfacing an LCD Screen to the 68HC12 Objective The objective of this lab is to learn how an LCD screen operates and to interface it to the 68HC12 by using a header file that contains the interface routines The screen will be used to display the answers generated by the magic eight ball program Preparation Read the LCD screen manual Interfacing a Hitachi HD44780 to a Motorola 68HC11 or Motorola 68HC12 Prelab 1 Become familiar with the different LCD screen functions included in LCD12 H http www ecse rpi edu Courses CStudio hcl2 sampleprograms 2 Rewrite your code from Lab 1 so that the answers from the program are displayed on the LCD screen The menu used to select the answer type is still displayed on the computer screen Project Description For this lab you will be adding an LCD screen to the Magic 8 Ball This screen will be used to display the answers that are generated by the program When an answer is written to the screen the screen should first be cleared and then the answer printed The answer should remain on the screen until a new answer is generated The different LCD functions are in the LCD12 H header file Helpful Hints Here are several suggestions to help you with the lab 1 Remember that all c
5. displayed on the screen In the later labs you will add a keypad for the input and an LCD for displaying the answers Preparation The preparation for this lab is very simple You should have a copy of the 68HC12 User s Manual which was provided in class This will be used as a reference for programming the 6812 and contains sample code that may be useful to you in your projects You should read the sections on programming the 6812 and using the DBugl2 monitor before coming to lab Prelab 1 Read the 68HC12 User s Manual 2 Develop a flowchart for the program you need to write This will be signed off by your TA and must be included when you turn in your code for the lab 3 A complete C program that meets all specifications stated in the project description Project Description For this project you will be developing an electronic Magic 8 Ball You will write a program that generates answers to different kinds of questions The user selects the type of answer that is desired and the answer is displayed on the screen There are four different types of answers that can be generated They are 1 Yes No This will output either a yes or no answer 2 True False This will output either true or false 3 Day of the week This will randomly select a day of the week 4 Random Number This will select a random integer number within any range stated by the user e
6. fy the use of pull ups See the sample code for this in the 68HC12 User s Manual 6 Remember the column select values are 1 2 4 8 not 1 2 3 4 Notes You may want to consider using a keypad for your final project One idea for this would be instead of returning the value to the main program to have the buttons call different functions which in effect allows the keypad to operate as a more advanced flexible version of the IRQ a mae eae Banana L Pins normaly pulled high through pull up resistors in gt 6812 switch dosure will temporally pull bit low gt Pins normally grounded held low Keypad wiring diagram The keypad is a passive device with only switches that connect wires on the crosspoint matrix of 4 x 4 wires
7. haracters to be sent to the screen must be sent as ASCII This can be done by creating a char with the character string or by passing in each character separately as an ASC character 2 Don t forget to include LCD12 H in your program 3 Remember to initialize the screen before trying to use it and that you have set the format type number of lines and character size to the desired value Lab 3 Interfacing a keypad to the 68HC12 Objectives The objective for this lab is to introduce a new feature of the 6812 the Key Wakeup interrupt and to demonstrate how to interface a keypad to a microprocessor This lab will also show you how to write your own header file for use with a microcontroller Preparation Read the section of the 68HC12 User s Manual that covers interrupts and the Key Wakeup interrupt Prelab Write a header file called keypad h that has the Key Wakeup Interrupt initialization routine and Interrupt Service Routine 2 Develop a new version of your code from Lab 2 that incorporates the header file and uses the keypad for all user input 3 Write a flow chart for the operation of the Key Wakeup Interrupt Service Routine Project Description This lab adds a keypad to the program that was developed in Lab 2 The keypad is connected to the microcontroller by the Key Wakeup Interrupt of Port J This will all
8. l tell you which column contains the key that was pressed but not the row of the key Note that the interrupt flag register should contain the same information Of the two which one will latch and which one may have a problem with contact bounce 3 Parse through the different rows to determine which key was pressed This step is the most complicated step of the process When a key is pressed the value on the low bits determines which column was activated Since the keypad we are ground for all the keys Port J is passed in through the row select bits determine which row is act row individually and then look at J pressed then th If the row you write a one to value on the low Your program needs to write a one is detected you will then look at the original termine which key was activated When the 1111 of the low bits to det For example Port J were previously assuming the pins for the has been wired to bit 3 of number 1 key 4 You must have a global This variable will program the main program can file the main variable 5 Reset actually 6 Wait for the key if row SO 0111 variab the ground tive the program must is active when then using does not have a common that is seen on the low bit of In order to write a high to each the value on the low nibble of Port is the row in which the button is bits of Port J will be 111
9. ow the keypad to operate on an interrupt based method The code for controlling the keypad will be located in a header file called keypad h This will allow the file to be easily transported to different programs The keypad used in the lab is a Greyhill series 96 4x4 keypad There are 8 pins connected to this keypad Four are used for the row select and 4 are used for the column select The 4 row select pins are normally connected to 4 port outputs bits that are held low When a button is pressed one of the column select pins will then go low which will trigger the Key Wakeup Interrupt The Key Wakeup Interrupt must then determine which row was activated and return the correct character for that button The code will consist of two functions One will be used to initialize the Key Wakeup Interrupt and the other will be the Key Wakeup ISR The initialization function must do the following Set Port J to detect falling edges Select Pull ups for Port J Enable pull ups Enable the Port J bits that will read in the column selects Set the row select bits for output 5 Oe WBNE 6 Write lows to the row select bits The Key Wakeup 1 Save the st ISR must do the following ate of the Key Wakeup Flags 2 Get the value of the 4 low order bits on Port J Hint use a mask The low bit in the 4 bit value wil
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