Aircraft Combat
Contents
1. time t tL Horizontal sync signal t front porch sets retrace frequency back porch Figure 4 Timing sequence of VGA controller 1 Figure 5 Final gameplay screen shot 4 3 7 Segment LED display The Nexys3 board contains a four digit common anode seven segment LED display We used this on board LED display to show the current level bullet soeed and movement speed The hardware design is just using an IP provided by Digilent so we simply connected it to our system and it works The IP has the soft controllable registers so the software part of our system can control the content to be shown on the display The display will scan itself and shows the corresponding values 4 4 GPIO input om parufor Logic pe LM324 10K 1 oTi cl 5 Ley 390A io sek lo Fa wa ote e 1c Ty 9 1 Qul Sve i T ON RAR Figure 6 Joystick controller schematic To control the movement of our plane we designed ajoystick which can be connected to the board The NEXYS 3 board provided some P MOD connectors that can be used as GPIO Inside the joystick we added one comparator circuit to measure the direction of the handle because the original joystick only provided two potentiometers And to generating the interrupt when moving the handle a NE555 timing circuit is added It can generate square wave signal which frequency is adjustable thus could control the speed of interrupt generation Figure 6 plots the schematic o2. Bus Interfaces Add resses Name Bus Name IP Type IP Version axidlite O Yr axi interco 1 06 a microblaze 0 dimb Tr Imbv10 2 00 b microblaze O ilmb jr Imb v10 2 00 b s 5 H microblaze ir microblaze 840 a T t microblaze Ol bram block jr bram block 1 00 a r H microblaze Old bram ctri ir imb bram i 310 a T E microblaze i bram ciri Yr imb bram i 310 a i Hh debug module ir mdm 210 a G axi inte Yr axi intc 1 02 a fd DIP Switches Bits Yr axigpio 1 01 b ST amp JOY Stick Yr axi_gpio 101b go day Buttons Xr axigpio 101b E LEDs 88its Yr axigpio 10l b Doo Push Buttons 4Bits Yr asi gpio 101 b S AXI axidlite 0 AS AXI axidlite ST i RS232 Uart 1 Yr axi uartlite 102 a fT sum seg axi 0 Yr svnseg si 100 a F EH ga acc e vga acc 1 00 a 5 0 8 AXI axi4lite_0 clock generator 0 Tr clock gene 4 03 a proc sys reset TI proc sys re 3 00 a Figure 2 System assembly view 4 1 Hardware Connection In our hardware connection we used AXI bus connection The AXI bus is a newer version and could provide more functions than old PLB bus We used BRAM in the processor to store the figures We also used GPIO resources provided by Xilinx To monitor the situation of the GPIO we added am interrupt module in our design It can sense the activities of the GPIOs The system assembly view is shown in Figure 2 4 2 Graphic accelerator To make the background smother and m
3. YOC GND S signals Bank Pine v EM ME Fin 12 mg mr e f a Banks Fmod Connectors front view as loaded an PCB Pmod Pinouts Semet JAT T12 JB 1 K2 JC 1 H3 JD1 G11 JAZ V12 JB2 KA JC2 L7 JD2 F10 JAS N10 des L4 JC3 K6 JD3 F11 JA P11 JB4 L3 JCA G3 JD4 E11 JAF MIO JB T J3 JC T G1 JD 7 D12 Bank0 JAB N9 JES J1 JC8 J JD8 C12 JAS D11 JBS K3 JC8 JE JD8 F12 Spartan 6 JA10 M11 JB10 K5 J10 F2 JD10 E12 Figure 9 PMOD connectors on Nexys 3 board 1 Customized Connector Adjustment Screw Vibration Switch Figure 10 The whole hardware system The device utilization is shown in list 2 Because we use distributed memory in VHDL so the usage of BRAM is quite low 11 Slices LUTs 3 847 9 112 Registers Memory List 2 Device Utilization in Nexys 3 fpga board 5 Software All software is written in C It is responsible for information in foreground including position of player and enemy position of bullet check if there s been any change in joy stick state and handling collision of objects in foreground 5 1 Display objects In our game software doesn t output the actual data of pixels Instead all pixel data of a picture is drew by hardware VGA accelerator while software gave hardware the position data of a certain picture The dimensions of the game window and objects are as Figure 11 320 Width 32 Height 32 Width 4 Height 10 Width 32 Height 32
4. Figure 11 Dimensions of the game window and objects 12 There are four kinds of objects need to be display on the screen player s aircraft enemies bullet and lives amp scores Each of them is handled by a function Display flight The function display flight is used to write the position data of player s aircraft to the slave registers Display enemy Function display enemy is used to write the data in which includes position and speed of a certain enemy to the slave registers The initial x position of enemy is determined by an array of random numbers which is generated in Matlab in advance However y position of enemy plane is calculated in this function to keep the enemy going down at the given speed Details of position calculation will be introduced later Display bullet Similar to display flight function display bullet writes position data of the bullet shot by the player s aircraft to the slave register Display lives score send data of lives remaining and score gained to the slave register 5 2 Initialize and move objects 5 2 1 Initialize and move enemies Apart from the functions manage to display objects there are several functions called for operating the game For example make the game seems more random To be more like a game the enemy should show up randomly random in x position and random in time with random speed In order to do so we have a function called enemy_showup to implement the randoml
5. each crash on enemy will decrease 1 live until live become O then game over The player can control the aircraft by using the joy stick by pressing the finger button on the joy stick the bullet speed increases Keep pressing the upper button the moving speeding of the player s aircraft increases The green button on the base of the joy stick is for turning on and off the vibration of the joy stick 17
6. We used the classical add 3 algorithm it is a pure combinational logic which is fast and easy to implement The module can input 10 bit binary and converts to 3 BCD numbers which requires 12 bit output in total 4 2 5 VGA REF COMP module The VGA REF COMP module handles the timing sequence of VGA display provides the horizontal and vertical counters to guide other blocks generate correct output to the VGA connector It uses a 25MHz clock signal to generate the HSYNC and VSYNC signal and two counters to count the clock When the H counter or V counter lies out of the visible area a blank signal is generated When H counter is counted to the end it resets to O and V counter increased by 1 The timing diagram is shown in Figure 4 1 The other modules should receive these two counter signals and generate the correct pixel to the VGA connector at each clock cycle When they detected the blank signal a black signal 000 should be outputted The screenshot of our game interface is shown in Figure 5 pixel 0 0 pixel 0 639 640 pixels per row are displayed during forward beam trace Retrace no information displayed during this time Display Surface pixel 479 0 pixel 479 639 Stable current ramp information is displayed during this time gt Current waveform through horizontal defletion Total horizontal time retrace coil po o Horizontal display time Y time HS
7. Aircraft Combat A mini game Yun Miao soc12ymi student lu se Siyu Tan soc12sta student lu se 16 10 2013 ABSTRACT This report documents the development of an aircraft combat game In this project the game is implemented on Digilent Nexys 3 FPGA Board with a VGA monitor and a custom designed GPIO joy stick The custom graphic accelerator is designed in VHDL to generate the game video and output to the VGA monitor while game logic software developed on MicroBlaze processor handles the game information and allows the user to play the game via an interrupt based joy stick connected through GPIO on board The game output resolution is 640x480 pixels 60 Hz CONTENT ATMA A A S CONTENT na ai 1 Moo ee E Bana E OVAC E na Na Na NA AA NA eee 1 2 Changes from project proposal o ooo WoooW onani 2 Pa ca T T UU uum 3 BSC IGN GON cR ETE E mc 4 BELE T A E OE E A E E Als Hardware Connecti m A dd A AA AA a 2 2 Ci g s area uote ene Ne nett AAA AAA AAA Aa AA A nee en A21 SomnWarecontgurable TERE fc Renee nee en ene oa A22 Background TNO US nn mint ii 423 Foreground node wt TET AA A nii AI GARE COMP ONS ea an Oo 43 PSCC LED display ET MEG dS iie a TTE 5 Sogar M 12 Sa Display eio ol os Om 12 5 2 Intake and MOVE ODJECTS ne disp ias 13 5 2 1 Jnitialize and move CHEIMES usssexeimre sx e hue el Eo FER
8. EN EV maa E eX Uo ra KAA AAA V BAN EUER GRAN Ra 13 5 2 2 Initialize and move player s aircraft ea am Y Fac ee cit ale lis ii 14 5 2 Collision GOL CTION TEE 14 Ss ICs score and c i Nm 15 0 5 ONET a o preg en A M EINEN NEM ERIS 16 6 Conclusions and de Kn 16 Gl Possible NTO ko A A ev eid AA A AA A A EMI Ces MINIM has 16 62 CONDUTOS ET uum 16 7 PRPS NC ft T HC 17 8 User mandi PEN NA PA PN NN PA NA AA RA PA 17 1 Introduction 1 1 0verall design The idea of this project is to design an Aircraft combat game The user can control an aircraft by using joy stick The aircraft is flying in a two dimension vertical scrolling space There will be enemies coming from top side of the space The player must avoid them or destroy them by using the auto firing cannon on the aircraft These objects will be displayed on a VGA monitor controlled by FPGA board Also the 7 segment display is used to display some game related values such as level and speed of the aircraft The design consists of a general purpose CPU Microblaze on the FPGA board and a graphic accelerator In this project AXI bus is used The CPU decides the content to be displayed while the graphic accelerator draws the content on the screen The final game outlook as shown in Figure 5 Memory Block 1 Stores instructions score and status etc 4 Monitor MicroBlaze Graphic VGA Joystick CPU ACC Controller Software Contigurable Registe
9. ake software design easier we put the foreground display background generation and score live display in to an individual VGA ACC module It is composed by VHDL which is called by the user logic module generated by Create or Import Peripheral function in XPS The module provided 10 software configurable registers which can be accessed by software and change the display contents in hardware The Block diagram can be seen in Figure 3 software configurable registers BIN BCD CORE BACKGROUND BIN BCD LIVE Figure 3 VGA accelerator VHDL block diagram 4 2 1 software configurable registers To access the hardware of VGA accelerator we need to use the software configurable registers Each of them is a 32 bit register and the value defined in software can be seen in the hardware So hardware core can use these values to change the position of various objects or update the score and live on the display The way how these registers communicate with the software is predefined in the user logic template so we could easily pass the value from the resisters to our top module inputs Register list is in list 1 Enemy position4 x y Reg4 24 16 Reg4 8 0 Bullet position x y Reg5 24 16 Reg5 8 0 Reg6 25 16 Reg6 9 0 List 1 software configurable registers and corrseponding VGA moudle input 4 2 2 Background module The background module only handles the background objects in our case is the flying cloud and the ba
10. ckground color We put the cloud figure in the LUT in VHDL and when the Hcount and Vcount counting to the correct point the cloud is ouput through VGA line to the monitor pixel by pixel To control the movement of the cloud we defined a counter to count the current vertical place of the cloud And at each refreshing the counter added by one and the cloud can move down one line Because the refreshing rate is 60fps so in this way the background cloud moving smoothly We also need to design the sky space where the plane can fly in blue and the gray surroundings 4 2 3 Foreground module The foreground generator takes care of the airplane and enemies which positions are loaded from software accessible registers So the location of both plane and enemies can be calculated by our software In our hardware we only designed four enemy position inputs It means that in one screen only maximum 4 enemies can be shown That is because we need to control the position of each enemy in real time to allow the movement speed controlling in software part In this way the input enemy position should be a limit number However when one enemy is shot another one will emerge soon So when the game starts due to the various place and speed of showing up enemy you can hardly think this number limitation is a problem 4 2 4 BIN BCD module Two BIN BCD modules control the scores or lives to be display on the display the binary value should be converted to BCD value
11. er 5 5 Other effects Vibration of the joy stick when the vibration function is turned on each time shot on an enemy the joy stick will vibrate for a short time Each time the aircraft crashes there will be a long time vibration As the joy stick is connected to the GPIO on the board to vibrate is just discrete write certain value to the specific pin on GPIO 1 for vibrate O for not vibrate e Aircraft boost when pressing the upper button on the joy stick the player s aircraft can have a faster moving speed as speed is changed from 5 pixels LT to 10 pixels LT This is controlled in main function e Aircraft shooting boost when the lower button is pressed the bullet speed will change from 15 pixels LT to 30 pixels LT This is controlled in main function 6 Conclusions and discussions In the project the game was built successfully and the game play logic was good but not perfect During gaming the enemies came into the screen randomly It felt like there were more than 4 enemies at a time in the screen because of the speed There were still some small bugs that sometimes the bullet couldn t hit on the enemy We think the reason is that the bullet flew 15 pixels LT or 20 pixels LT while the height of the enemy is 32 pixels When the speed of the enemy is fast enough the bullet won t hit on it 6 1 Possible improvements e First of all the graphic can be improved by introducing BRAM into the system which can store mo
12. f our circuits and Figure 7 is the inside view of the joystick Figure 7 Inside the joystick We added a vibration module to make the game more realistic It is just a small motor with a tiny heat sink as the vibration module When the input signal is high it will power on by the internal battery and generate the vibration effect in your hand which is so cool The picture is shown in Figure 8 Figure 8 Vibration module inside the handle The P mod connectors are designed for connecting external hardware components In Nexys 3 board four groups of P mod connectors are provided as demonstrated in figure 9 We used Pmod A for our Joystick input JA1 JA4 are for four directions of the Joystick JA7 is for vibration output JA8 and JA9 are two buttons input on the handle It could be configured in the XPS hardware platform and can also be connected to the interrupt module The whole system is illustrated in figure 10 The controller has four directions which could control the movement of the plane There is a small screw on the left which is designed to adjust the frequency of the interrupt frequency The green button is used to switch the vibration module which can reduce the noise when debugging our program The top button on the handle is used to control the movement speed of the plane and the button placing at finger could control the bullet speed The Joystick is connected to the Nexys 3 board by our customized 12 pin connector 10
13. pe 14 Collision of enemy and player s aircraft is detected as Figure 14 In the figure the green frame indicates the boundary of the aircraft s original point When the original point is inside the green frame enemy and the aircraft is considered crash with each other So the if case is designed like List 4 In the list x pos and y pos are the position of player s aircraft enemy1_x and enemy1_y are the position of the enemy if y pos x pos enemy1 x 32 enemy1 y amp amp y pos 32 enemy1 x x posrenemy1 y amp amp x pos enemy1 xt32 amp amp x pos enemy1 x 32 amp amp y pos enemy1 y 20 amp amp y_pos lt enemy1_y 20 enemy1_y 0 live 1 List 4 if case for collision detection of enemy and aircraft Figure 14 enemy and aircraft collision detection The collision of bullet and enemy is easier as bullet flies fast the collision can be detect using only the square of enemy and the rectangular of bullet 5 4 Live score and level In the game player will have 5 lives Lives will decrease when aircraft crash on enemy When live becomes zero the scores gained will decrease continuously to zero while live increase back to five 15 The counting of score is related with level In level 1 every shot on enemy will add 1 to score with each increase of level the scores gained at each shot increases by one Level will go up when score reaches 50 150 250 and the game speed will be fast
14. re complex pictures But the problem of smooth scrolling needs to be solved e More enemies could be added not only in quantity but also in type even bosses could be introduced e We ve think about adding sound module but as the time is limited we didn t work it out 6 2 Contributions During the project Tan Siyu is mainly in charge of the hardware design including the VHDL coding the built up of the joystick as well as hardware test On the other hand Miao Yun is focusing on the software coding and the graphic for the objects 16 7 References 1 Digilent Nexys 3 manuals and drivers http www digilentinc com Products Detail cfm NavPath 2 400 897 amp Prod NEXYS3 2 Project 2012 TowerDefence http cs Ith se english course eda385 design of embedded systems advanced course archive projects 2012 8 User manual To play the game plug in the USB connector to the board connect the joy stick to the Pmod connector according to the direction indicated on the connector of the joy stick In the screen the green aircraft flying upward is the player s aircraft while all enemies are flying downwards Player s aircraft will shoot bullet automatically bullet can eliminate enemy while player s aircraft will crash on the enemies Every enemy killed will add some bonus to the final score at level 1 the bonus is 1 Level 2 leads to 2 bonus etc When score reaches 50 150 250 the level increase Player will have 5 lives at beginning
15. rs Memory Block 2 Stores position of Stores objects shape foreground objects LT Figure 1 Hardware block diagram 1 2 Changes from project proposal As the game is a mini one and for simplifies the design BRAMs are not used All objects are stored in the VGA accelerator using distribute memory Instead of PLB bus the game is implemented using AXI bus The C program is not interrupted every frame it is looping with a delay and in the following of this report LT stands for loop time indicate the time for one loop of the while statement in C program The program is only interrupted by the direction control from joy stick 2 Equipment In this project the following equipment was used e Digilent Nexys 3 Spartan 6 FPGA Board e Digilent PmodA Joy stick e VGA monitor e PC computer running Xilinx EDK v 14 2 To run the system the following equipment was need e Digilent Nexys 3 Spartan 6 FPGA Board Digilent Adept to program the board Digilent PmodA Joy stick e VGA monitor 3 Specifications The system was able do the following e Output graphics to a VGA monitor with a resolution of 640x480 pixels 0 60Hz e Update the player s position by moving the joy stick e Update the game with enemy aircrafts at different times Detect collisions between the player s aircraft and enemy aircrafts And in a similar way detect collisions between the bullet shot by the player and enemy aircraft 4 Hardware
16. ue read till 0 then again enable display enemy again 5 2 2 Initialize and move player s aircraft The player s aircraft is initialized in the middle bottom position The movement of the aircraft is implemented by an interrupt Every movement on the joy stick will trigger the interrupt With the different signals of direction the aircraft is moved certain pixels according to integer speed The bullet is shot from the head of aircraft the speed of bullet is determined to be either 15 pixels LT or 30 pixels LT according to the state of button on the joy stick Then display bullet is called When the player s aircraft is crash on the enemy the aircraft will blink to indicate dead Function blink is called to implement blink To make the aircraft disappear is to write zeros to slave registers which controls the display of player s aircraft Whole blink duration last for 80 clock cycles and blink twice 5 3 Collision detection The collision of bullet shot on enemy and player s aircraft crash on enemy are handled by two if case in main function As all objects are considered as squares while upper left corner is original point collision detection can be easily done by comparing the position of objects But for better detection enemy is considered as shown in Figure 12 and player s aircraft is the same as enemy but upsidedown Figure 13 lt 16 a Figure 12 Enemy shape for collision detection Figure 13 Player s aircraft sha
17. y showing up in time and some if cases in main to handle random position and speed The random we carried out is pseudo random which base on three set of arrays where stored the random number generated in Matlab in advance For x position 300 random numbers are stored in rand pos in range from 1 to 288 This is because the width of the game window is 320 while the width of enemy is 32 and upper left corner is regarded as original point For random speed of enemy 100 random number are stored in rand speed in range from 1 to 3 The speed value determines how many pixels the enemy moves in one loop time For random delay before next show up of the enemy 200 random number are stored in rand wait in range from 1 to 500 The wait time determines the clock cycles before next show up The if case as show in List 3 first decide which enemy to be activate and take number one by one from both rand pos and rand speed with the help of a counter Then send the value to display enemy function to display if enemy1_y 1 pos_cnt pos_cnt lt pos_length pos_cnt 1 0 speed_cnt speed_cnt lt speed_length speed_cnt 1 0 13 enemy1 x rand pos pos cnt speed1 rand speed speed cnt j List 3 if case for enemy set up After the enemy flies out of the screen or be eliminated it should show up after the delay This is handled by function enemy showup the function first read a value from rand wait and count down from the val
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