COMPUTER ENGINEERING PROGRAM

Transcription

1 COMPUTER ENGINEERING PROGRAM California Polytechnic State University CPE 169 Experiment 1 Introduction to Basic Logic and the Digilent Development Board Learning Objectives 1. CPE 169 Hardware and Software To become familiar with the courseware and laboratory procedures 2. Introduction to a Digital System To become familiar with analyzing a digital system Introduction and Overview The Digilent Nexys2 development board is your primary hardware platform throughout CPE 169. Your overall objective in this experiment is to become familiar with and comfortable using this board and some of the associated software tools. A more thorough and in-depth description of the development board is presented in later experiments though your strongly encouraged to peruse the reference manual associated with the development board (located on the course website). You ll also become more familiar with the software as the quarter progresses. Figure 1 shows the Nexys2 development board, with arrows pointing out some of the more interesting features. Figure 1: The Nexys 2 board with pertinent parts indicated. 1/29/

2 The development board can be considered a complete digital system. The board contains various devices that act as inputs and other devices that act as outputs. For this experiment, several inputs and outputs are not used so they are omitted from the discussion at this point. The set of external inputs to the development board that you ll work with in this experiment include four push-buttons and eight slide switches. The external outputs that you ll work with are the eight light emitting diodes (LEDs) and two of the four 7- segment displays. Figure 2 shows a high-level black-box diagram of the digital system on the development board as you ll use it in this experiment. Figure 2: System-level black-box diagram of the development board for this experiment. Figure 2 shows notation that is used throughout CPE 169 and in digital design in general. In Figure 2, the arrows entering the box are used to indicate input signals while the arrows leaving the box are used to indicate output signals. The slashes across the signal lines indicate that there is more than one signal associated with the single line in the diagram. The number of signals represented by the line is indicated with the number near the slash. The notation used in Figure 2 provides a quick method to indicate that the system contains four buttons, eight switches, eight LEDs, and eight display segments. Any one of these related groups of signals is referred to as a bus, or possibly more appropriately, a bundle. The heart of the development board is a type of programmable logic device known as a fieldprogrammable gate array (FPGA). All you need to know about this device for this experiment is the fact that the device is programmable. This means that you can change the relationship between the input and output devices on the development board by downloading special files to the FPGA. In this experiment, you ll be downloading different circuit descriptions to the FPGA and analyzing the input and output characteristics of the downloaded circuit using the buttons, switches, LEDs, and 7-segment displays on the development board. The procedure to download files into the FPGA is listed in the following procedure portion of this experiment. Procedures Procedure Overview: There are two main procedures associated with this experiment. Both procedures involve the downloading of configuration files to the development board. Each configuration alters the relationship between the input and output devices shown in Figure 2. Your task in this experiment is to download each of the configurations to the FPGA in order to analyze and describe those relationships. The first procedure consists mainly of a demonstration of the capabilities of the development board. The second procedure requires that you analyze five different configurations on the development board. The FPGA input/output relationships in these configurations start out relatively simple but become more complex as you proceed through the configurations. Instructions to Prepare Development Board for Configuration: 1. Configure the jumpers on the development board to allow for programming the FPGA via the USB port, and to provide the proper power supply to the expansion connectors for later experiments. a. JP7 Power Select: Jumper on "USB" pins (across 2 bottom-most pins) b. JP9 Mode: Jumper on "JTAG" (across left-most 2 pins) c. JP1, JP2, JP3, JP5: Jumper on 3V3 (across middle & bottom pins) 1/29/

3 2. Connect the USB adapter cable supplied with your development board between the female USB port cable on the Laboratory PC and the mini USB connector on the development board 3. Apply power to the Development Board and verify that power is ON. a. The Nexys2 Board has its own POWER switch (located in the upper left corner of the board) which must be switched ON. b. A red LED labeled LD2V5 POWER is lit when power is on. 4. Provide the device ID and serial number for your development board to the Digilent USB programming tools. a. From the Windows Start Menu, select All Programs Digilent Adept USB Administrator. A new Digilent USB Administrator window should appear. b. Click on the numbers that appear in the window to reveal the Details. c. From the Windows Start Menu, select All Programs Digilent Adept ExPort. A new Digilent ExPort window should appear. d. Select Edit Configure Communications Modules A new Communication Modules window should appear. e. If the Serial number for your development board (found in the Digilent USB Administrator window) does not appear in the Select/ID column of the Communication Modules window, then: a. In the Communication Modules window, select Add Module USB b. In the Add Module window: 1. Click on your development board s serial number in the Connected Modules field. 2. Type in a name to uniquely identify your development board in the Device Name field. (The name is arbitrary, so use a name you will recognize as your own when you return to the lab in the future.) 3. Click on Add, and Done. c. In the Communication Modules window, select Save, and Close. f. Close the USB Administrator window. Instructions to Configure FPGA: There are several FPGA configuration files listed under Experiment 1 on the laboratory website (the ones with the.bit file extension). These files provide a description of a circuit that you ll download to the FPGA to program its internal circuitry. The procedure to download a file to the FPGA using the Digilent USB tools is listed below. Be sure to first verify that the development board is powered up and the appropriate programming cable is connected to the board. 1. Download the FPGA configuration files for this experiment (.bit files for the Nexys Board) listed on the class website to your PC desktop. 2. If the Digilent ExPort tool is not already open, then from the Windows Start Menu, select All Programs Digilent Adept ExPort. 3. In the Digilent ExPort window, make sure that the box marked Auto-Detect USB is checked. If not, click on the box until a check mark appears. 4. In the Digilent ExPort window, click on the Initialize Chain radio button. Two devices should appear in the window; one marked FPGA and one marked ROM. These are the two programmable devices on the development board. The FPGA contains the digital logic circuitry that you will be configuring and testing. The ROM device provides a place to store the FPGA configuration for automatic reprogramming when the development board is powered on. 5. Next to the FPGA device, click on the Browse.. button. 6. In the window that appears, browse to the Desktop and select one of the configuration (.bit) files you previously stored, and click on Open. (NOTE: A Warning message may appear with some 1/29/

4 undecipherable gibberish about CCLK and JTAG. Just click Yes to clear the message). The name of the configuration file you selected should now appear next to the FPGA device. 7. Right-click on the FPGA device in the diagram and click on the Program Device option in the pull-down menu that appears. (Or alternatively, just click on the Program Chain button.) 8. If the programming was successful, "Programming complete Succeeded" will appear in a new Programming window. Click on the OK button. In addition, the yellow DONE indicator (LD- D) will light when programming is completed. 9. The FPGA can be reprogrammed with a different configuration file at any time. To do so, repeat Steps 5 8 above. Procedure 1: Development Board Demonstration and Analysis Configuration Overview: The configuration for this procedure was designed to provide a demonstration of some of the capabilities of the development board. More specifically, this circuit demonstrates some typical applications for the 7-segment displays and relatively interesting visual events relating to the buttons and LEDs. It is your task to use various combinations of button presses to perform different functions on the development board and provided a description of the results. 1. Configure the development board with the demonstration configuration file: nexys2_demo.bit. 2. Set the eight switches (SW7 SW0) on the board to your choice of Up/Down pattern, other than all Up (HIGH) or all Down (LOW). 3. On the development board, simultaneously press two, one, or no buttons and describe the response observed on the board. Assemble your results from this step into tabular form (put your results in a table) and include it in your lab report. [HINT: Since there are four buttons, your table should have no more than 16 entries. However, since you only need to test for at most two simultaneous button presses, your table does not require listing all 16 possible combinations of pressed and nonpressed buttons.] Use the table format shown in the example in Table 1. Indicate a button that is pressed for a particular result using an "X" in its column in the table. Leave the table entries blank for any switches that are not pressed for a particular display result. Use button names in your table that match their designations on the development board. Be sure to also include a system-level black-box diagram of the digital system you are testing in your lab report. BTN3 BTN2 BTN1 BTN0 Description of Development Board Display Results X Development board explodes violently X Lab partner passes out X Alien beings take control of development board Table 1: Example table and headings for the results of Procedure 1. 1/29/

5 Procedure 2: Development Board LED Analysis Configuration Overview: Each of the configuration files allows the LEDs (outputs) on the development board to be driven by actuating a single or some combination of buttons or switches (inputs). These five files are used on different levels where the higher levels indicate that more complex input conditions are required to light an LED. For each level, you are to find the input combination or combinations that turns on each of the LEDs. Your mission is to find and list what those relationships are. There are eight LEDs so you ll need to find eight relationships for each level. To help you with this daunting task, certain guidelines are provided for you and are listed in Table 2. Level Number of Inputs per LED Input Combination Description Number of Combinations that turn on each LED 1 1 either one button or one switch one button and one switch one button and one switch one button and two switches two buttons and two switches? Table 2: Guidelines for configuration file analysis. Development Board LED Analysis: 1. Configure the development board with the configuration file nexys2_level1.bit. 2. Using Table 2 as a guideline, determine what input settings (combinations of switches and buttons) are required to turn on each of the eight LEDs (outputs). Consider a button to be on when pressed and off when not pressed. Consider a switch to be on when in the up position and off when in the down position. 3. Assemble your results (the switch/button combinations that turn on each of the LEDs) in tabular form. Be sure to include a system-level black-box diagram of the digital system you are testing in your lab report. 4. Repeat the previous steps for levels 2-5. The configuration files are named according to the level you are executing (i.e., nexys2_level2.bit, nexys2_level3.bit, etc.). NOTE: Level 3 requires that you find two different combinations of switches and buttons that make each LED light up. You must list both possibilities. NOTE: Level 5 is somewhat complex. If you can figure out how to individually turn on each of the eight LEDs using the Level 5 configuration file without assistance from an instructor or other students, you will receive an A in CPE 169 and will not be required to perform any more of the experiments. (However, be sure to ask the instructor for the secret approach to dealing with this level before becoming too frustrated!) 1/29/

6 Questions 1. In Procedure 1, your testing consisted of pressing different combinations of the four buttons. How many unique button combinations would have been possible given the four buttons if all combinations were allowed (with 4, 3, 2, 1 or no buttons pressed)? 2. With the four buttons used in Procedure 1, how many unique button combinations were possible under each of the following specific conditions? Briefly state the method you used to answer this question. a. only one button pressed b. only two buttons pressed c. only two or three buttons pressed 3. The Level-4 combinations were relatively complicated. Describe your strategy for figuring out the input combinations without losing your sanity. 4. Familiarize yourself with the basic operation of the Nexys2 development board by reading the first few sections of the Nexys2 Reference Manual (Overview, Functional Description, FPGA and Platform Flash Configuration), available on the class website. Is the FPGA used in this experiment on the Nexys2 board considered to be a volatile or a non-volatile device? Describe the difference between these two device types. 5. What oscillation frequency is used for the primary system timing clock oscillator on the Nexys2 board? 6. The FPGA used in this experiment is considered to be a re-configurable device. How many different circuit configurations were used in this experiment? 7. In terms of inputs, outputs, digital systems, components on the Development Board, and the files you downloaded to the board; completely describe exactly what you did in this experiment in your own words. What exactly did you download to your board? Where did this downloaded information reside on the board once downloaded? What happened as a result of downloading this information (what did it accomplish or change)? What were the inputs to your digital systems? What were the outputs? By manipulating the buttons and switches on the board, what exactly were you providing to the system? What makes the devices you tested a digital system? 8. Despite the fact that there are 7-segment displays on the development board, there are eight signals used to drive the displays (see Figure 2). Briefly describe why the 7-segment display has eight signals. 1/29/