CS/EE 3720 Handout #4Spring 2005MyersLAB #4: Gadfly Keypad InterfaceLab writeup is due to your TA at the beginning of your next scheduled lab. Don’t put this off tothe last minute! There is pre-lab work to complete before the start of the next lab. NO LATELAB REPORTS WILL BE ACCEPTED.1 Objectives• Design the hardware interface between a keypad and microcomputer.• Create the low-level gadfly device driver that can be used in other applications.• Design the hardware interface between a microcomputer and a single LED.• Implement keypad security system.2 Reading• Read section 2.7 about writing software device drivers.• Read section 8.1 about keyboard scanning and debouncing.• Description of the keypad (see link on our website).3 BackgroundThe keypad interface will be designed in two parts. In this lab, you will use gadfly synchronization.In the next lab, you will redesign it using interrupts. This lab demonstrates how a parallel port of themicrocomputer can be used to control a keypad matrix. The keypad that you will be using has onecommon pin and one output for each key. The pins and the keypad are (pin=[key]): 1=Common,2=N/A, 3=[*], 4=[7], 5=[4], 6=[1], 7=[0], 8=[8], 9=[5], 10=[2], 11=[#], 12=[9], 13=[6], 14=[3].Your low-level software should input, scan, debounce, and save keystrokes. It should also handletwo key rollover. For example, if I type “1,2,3”, I may push “1”, push “2”, release “1”, push “3”,release “2”, then release “3”.4 PartsThis lab will require a 12-key keypad which you can purchase in the ECE lab. You can use this orany 12-key keypad to do this lab. If you do find your own keypad, be sure you have specificationsfor it.5 SoftwareBelow is a prototype for your device driver:1. Data structures: global, protected (accessed only by device driver, not the user)OpenFlag - Boolean that is true if the keyboard port is open, initially false, set to true byKeyOpen, set to false by KeyClose , should be in static storage.2. Initialization routines (called by user)KeyOpen - Initialization of the keyboard port, sets OpenFlag to true, initializes the hardware,returns error code if unsuccessful (hardware non-existent, already open, etc.), no input pa-rameters, output parameter is error code.KeyClose - release of keyboard port, sets OpenFlag to false, returns error code if not previ-ously open.3. Regular I/O calls (called by user to perform I/O)KeyIn - input an key value from the keyboard port, waits for key to be pressed, then waits forit to be released, should support debouncing and two key rollover, returns data if successful,returns error code if unsucessful (device not open, etc.).KeyStatus - returns the status of the keyboard port, returns true if a call to KeyIn wouldreturn with a key, returns false if a call to KeyIn would not return right away, but rather itwould wait.4. Support software (none in this lab, later you will add interrupt handlers here).6 TasksNote: In order to use lab time efficiently, you should complete the first 3 tasks before your labsection.1. Prepare a schematic for your design including all chips, pin numbers, and resistor values(note, you will need pull-up resistors on all the keypad inputs).2. Write your low-level keypad device driver.3. Write a main program which is an access code based s ec urity system.(a) Each access code will consist of 4 digits be tween 0-9.(b) The security system can recognize up to five access codes.(c) These codes will be specified in global memory.(d) The keypad will be used to enter these access codes.(e) If the access code is valid, an LED is turned on and remains on until a new key is pressed.4. Connect your circuit and debug your software.5. Use a scope to measure the bounce time and verify the sharpness of the digital inputs/outputs.7 WriteupInclude the following items. In this lab, only one writeup per team is required.1. Your hardware schematic.2. A printout of your assembly code.3. Collect some bounce time measurements and
View Full Document
Unlocking...