F19: Tower Defense in Space
Contents
- 1 Grading Criteria
- 2 Tower Defense...In Space!
- 3 Abstract
- 4 Introduction and Objectives
- 5 Team Members
- 6 Schedule
- 7 Bill of Materials
- 8 Game Design
- 9 Hardware Design - Electrical
- 10 Hardware Design (Mechanical)
- 11 Hardware Integration
- 12 Software Design
- 13 System Testing and Validation
- 14 Technical Challenges
- 15 Conclusion
Grading Criteria
- How well is Software & Hardware Design described?
- How well can this report be used to reproduce this project?
- Code Quality
- Overall Report Quality:
- Software Block Diagrams
- Hardware Block Diagrams
- Schematic Quality
- Quality of technical challenges and solutions adopted.
Tower Defense...In Space!
Background of the game
Abstract
This project involves creating and developing a video game where output is displayed on a LED matrix. Development of the relevant hardware/software components and modules was divided among 4 team members. Each team member lead or significantly contributed to the development of multiple components. The project was focused on not only technical skills, but team building as well, and working with others towards a common goal.
(Will revise this later CCH) This project provides us hands-on experience using freeRTOS in a real application. Our objective is to apply what we have learned in class and develop a game using our SJtwo Board. In this project, we need to use both cooperative scheduling and preemptive scheduling technique to make this game run efficiently. We create tasks for displaying the game objects on LED matrix, moving enemies, shooting enemies, and managing game stages. We also need to synchronize and sequentialize each task by setting the task priorities carefully and using binary semaphore.
Introduction and Objectives
Like most traditional tower defense games, the player needs to defend the homeland from the invasion of aliens. The player can place different kinds of towers strategically that attack the invading aliens from entering into our homeland by shooting the enemies. If any enemy spaceship reaches the end of the path, then the player loses. If there are no more spaceships remaining in a wave, the player can build a stronger tower that has a longer attack range and can shoot a more powerful death-ray against the spaceships in the next wave. The player wins the game after surviving 5 waves of attack.
This game can be separated into 4 different modules:
- Game: SJtwo Board - handles the game logic. (For example: detect and shoot nearby enemies, switch between intermission phase and combat phase)
- Display: Adafruit 64x64 LED matrix - displays the animation of the game.
- Gamepad Controller: The input of this game. The gamepad controller consists of a joystick and two buttons. The player can use the joystick to move the cursor and decide where to place the towers. After that, the user needs to press the black button to select and confirm the location of the towers. If the player knows that he will lose the game in the middle of the game, the player can press the red button to restart the game.
- Sound: MP3 Decoder and speaker. Players can enjoy cool music during the game.
Team Members
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TEAM MEMBERS & RESPONSIBILITIES | ||||
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Team Members |
Administrative Roles |
Technical Roles | ||
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Team Lead |
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Git Repo Manager |
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Wiki Report Manager |
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Bill of Materials Manager |
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Schedule
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TEAM MEETING DATES & DELIVERABLES | ||||
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Week# |
Date Assigned |
Deliverables |
Status | |
| 1 | 10/15/19 |
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| 2 | 10/22/19 |
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| 3 | 10/29/19 |
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| 4 | 11/5/19 |
Kelvin
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| 5 | 11/12/19 |
Kelvin
Polin
Ryan
Zach
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| 6 | 11/19/19 |
Kelvin
Polin
Ryan
Zach
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| 7 | 11/26/19 |
Kelvin
Polin
Ryan
Zach
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| 8 | 12/3/19 |
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| 9 | 12/10/19 |
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Bill of Materials
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Top Level | ||||
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PART NAME |
PART MODEL & SOURCE |
QUANTITY |
COST PER UNIT (USD) | |
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| 64x64 RGB LED Matrix* | Adafruit | 1 | $104.07 | |
| 5V 4A PSU | - | 1 | FREE | |
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Breakout Board PCB** | ||||
|---|---|---|---|---|
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Item # |
PART NAME |
PART SOURCE |
QUANTITY |
COST PER UNIT (USD) |
| 1 | IC REG LINEAR LD1117S33CTR | DIGIKEY | 5 | $0.351 |
| 2 | MHS16N-ND 16POS CONN 2.54MM | DIGIKEY | 2 | $2.60 |
| 3 | CAP CER 0.1UF 25V X7R 1206 | DIGIKEY | 5 | $0.221 |
| 4 | CAP CER 10UF 16V X5R 1206 | DIGIKEY | 5 | $0.202 |
| 5 | RES SMD 470 OHM 1% 1/4W 1206 | DIGIKEY | 10 | $0.0267 |
| 6 | PTC RESET FUSE 24V 500MA 1206 | DIGIKEY | 10 | $0.1588 |
| 7 | CONN SOCKET 40POS 0.1 TIN PCB | DIGIKEY | 2 | $5.03 |
| 8 | Manufacturing x 5 boards * | JLCPCB | 1 | $29.81 |
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Gamepad PCB** | ||||
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Item # |
PART NAME |
PART SOURCE |
QUANTITY |
COST PER UNIT (USD) |
| 1 | Analog 2-axis Thumb Joystick w/ select button | Amazon | 1 | $7.67 |
| 2 | SAM8205-ND 10POS 1.27MM | DIGIKEY | 5 | $3.38 |
| 3 | LED GREEN 1206 SMD | DIGIKEY | 5 | $0.24 |
| 4 | LED RED 1206 SMD | DIGIKEY | 5 | $0.257 |
| 5 | RES 1K OHM 1% 1/2W 1206 SMD | DIGIKEY | 5 | 0.0358 |
| 6 | CAP CER 0.1UF 50V X7R 1206 | DIGIKEY | 5 | $0.088 |
| 7 | 12x12x7.3mm Tactile Push Button w/ cap (pack of 25) | Amazon | 1 | $7.89 |
| 8 | Manufacturing x 5 boards * | JLCPCB | 1 | $14.21 |
* Shipping and tax included in value shown in the cost per unit column
** Only parts that were purchased are displayed.
Game Design
Gameplay is split into 2 stages:
Intermission:
Player sets up tower locations
Combat phase:
Player watches round unfold
During the Intermission stage:
The player places towers strategically around the enemy path.
The number of towers is fixed per round
Towers can only be placed in marked areas that do not lie on a path
(OPTIONAL) towers upgradeable
Maybe have 2 types of towers (different dmg and range) if code is written to scale
During the Combat stage:
Enemies will enter the gameplay area at one end of the path and attempt to reach the other end
Towers will automatically engage enemies when they come within range
Shoot until the enemy is either dead or out of range
Tower proximity is 8 directions (top, bot, left, right, top-right, top-left, bot-left, bot-right) and 1 unit (not necessarily 1 pixel) away
Enemies that reach the end alive will result in a life taken from the player. If the players lives run out the player loses and the game ends
The round is over when the player loses or a set number of enemies have been defeated.
There will be a dashboard on the LED matrix that displays basic UI information
Number of lives left (total across all rounds)
Number of enemies alive/total in current round
Time until combat phase
Current round number
Number of towers left that you can place
Rules and Objectives
There are 5 waves (rounds) total. In each round, enemies in various amounts, groupings, and health levels (armor) pass through the path. If any enemies reach the end of the path, then the user loses. After each round, the user will be able to place more towers which are stronger and can shoot farther. Each round will have waves of enemies that are more difficult to stop. The user needs to carefully place their towers such that it will have a maximum number of opportunities to shoot at the enemies. The trick is that the user will need to preserve early level towers, otherwise they will not have enough room to place the high level towers in the optimal location.
How To Play
Hardware Design - Electrical
Overview
At a high level hardware integration requirements fell into two categories:
1. Reduce risk of unreliable cable connections and eliminate possibility of damage to components through unexpected disconnections, power surges, etc.
2. Provide a more fluid physical interface for the user to interact with the game via hardware
To accomplish these goals, two boards were designed: a breakout board and a gamepad controller. The breakout board serves as a connection hub between all system hardware components; power, the RGB matrix, the SJTWO board, etc. while the joystick provides a cleaner package to present the user with the games inputs. The diagram below shows the relationship between the main subsystems:
All board designs were done using EAGLE and manufactured by JLCPCB. Both boards were only two layers and used passive components for the most part.
Breakout Board Design
The breakout board design requirement was to interface all external hardware components with the embedded system (SJTWO). The hardware connections are:
1. The 64x64 RGB Matrix
2. Output power to the RGB Matrix
3. User game controller (see next section)
4. Input power supply (5V)
5. The SJTWO embedded system
Known Breakout PCB Issues
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Known Issues | ||||
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Summary |
Description |
Version |
Status | |
| 5V should not be routed to game controller. | 3.3V should be routed to the game controller instead of 5V since the ADC pins are not 5V tolerant. | 0.1 | Resolved Rev 0.2 | |
| Wrong silkscreen/not enough room near power input. | Power input silkscreen too small, part too big for 3.3V LED to fit | 0.1 | Resolved Rev 0.2 | |
| Linear regulator not needed. | The schematic for the SJTWO board labels the input voltage pin as VIN RAW, which is different than the label on the
optional input port. They are both the same, so this input feeds directly into the on-board 3.3V regulator. Essentially we're driving the regulator with the same voltage it outputs which just won't work well. |
0.1, 0.2 | UNRESOLVED | |
Gamepad Hardware Design
The gamepad board design requirement was to provide a more packaged interface for the user to interact with the game.
Hardware Design (Mechanical)
Only a few mechanical components were needed for this project. Namely simple brackets for mounting electrical hardware to the RGB matrix and displaying the matrix itself. All CAD designs were done using Onshape, a free CAD tool that can be used entirely through your web browser.
For displaying the RGB matrix, two brackets were 3D printed to prop it up. Their STL files can be found under our source repository.
Hardware Integration
RGB LED MATRIX
The LED matrix that we use is 64 pixels by 64 pixels and is controlled through a 12-pin header consisting of the following pins:
- Five Mux pins (A,B,C,D,E) for Row Selection
- In order to select a specific row of the LED matrix, we need to control the output level of each mux pin. Since the LED matrix light up two rows of LEDs at one time, we can only select 1 out of 32 rows.
- Two sets of RGB pins (R1,G1,B1,R2,G2,B2) for Color Selection
- Since we are driving two rows of LED matrix at once, we need 2 sets of RGB pins. One set is used to control the color pixels of the upper half of the display and the other set for the bottom half of the display.
- Output Enable Pin (OE)
- Output Enable (OE) pin is used to turn on or off the LEDs of the current row.
- Latch Pin (LAT)
- Latch pin is used to prevent the data being shifted into the shift registers and tells the shift register when it is time to switch to newly entered data.
- Clock Pin (CLK)
- triggers a shift on the shift registers
All these pins are required to display a specific color on a specific pixel of the LED matrix display.
Apparently, it is impossible to driver all 4096 LEDs all at one time and thus, we can only drive two rows of LEDs at a time (one row on the upper half of the display and another row on the lower half of the display). By refreshing the LED matrix two rows at a time in a fast frequency, we can display all the game objects with animation on the LED matrix.
Joysticker controller
The joystick that we use is the product from Adafruit, the Analog 2-axis Thumb Joystick. This 2-axis Thumb Joystick provides the following pins:
- two ADC pin
- In order to control the tower location, we need to control the Joysticker, since the direction has four: Up, Down, Left, Right, we use the Y and X-axis to implement this function.
- Three GPIO pin
- In order for selecting for the tool we need two GPIO pin for button and 1 GPIO pin for controlling the LED on the JOY STICKER controller
MP3 Decoder
The MP3 decoder that we use is Sparkfun’s vs1053 shield MP3 decoder which is the board based on the vs1053b chip.
Software Design
RGB LED Matrix
All the LED Matrix data are stored in a buffer with its size equal to 32 by 64. Each element in this buffer store the color of two pixels, one pixel from the upper half of the display and one pixel from the lower half of the display.
In order to display the gaming objects in animation, we need to refresh the display by displaying the color pixels on each row one by one very fast. Below is a simple flowchart that describes the process of refreshing the display.
- Loop through each row of the LED display
- Select Row (By controlling the output level of 5 mux pins, we can select one row at a time)
- Disable the LED Display output (Turn off the LEDs of the current row of the display)
- Unlatch the Data
- Clock in Data for each column(Store the color of each pixel inside display_matrix buffer)
- Latch the Data
- Enable the LED Display output (Display the color of each pixel of the current row)
- Delay for a 100us (Increase the light intensity of the LEDs by delay a short amount of time)
- Disable the LED Display output (Turn off the LEDs of the current row of the display)
void refreshDisplay(void) {
for (uint8_t row = 0; row < LEDMATRIX_HALF_HEIGHT; row++) {
select_row(row);
led_matrix__disable_output(); // gpio__set(OE);
led_matrix__unlatch_data(); // gpio__set(LAT);
led_matrix__clock_in_data(row);
led_matrix__latch_data(); // gpio__reset(LAT);
led_matrix__enable_output(); // gpio__reset(OE);
delay__us(100); // Change Brightness
led_matrix__disable_output();
}
}void led_matrix__clock_in_data(uint8_t row) {
for (uint8_t col = 0; col < LEDMATRIX_WIDTH; col++) {
LPC_GPIO1->PIN &= ~(0x1 << R1.pin_number | 0x1 << G1.pin_number | 0x1 << B1.pin_number);
LPC_GPIO2->PIN &= ~(0x1 << R2.pin_number | 0x1 << G2.pin_number | 0x1 << B2.pin_number);
LPC_GPIO1->PIN |= ((((display_matrix[row][col] >> 0) & 0x1) << R1.pin_number) |
(((display_matrix[row][col] >> 1) & 0x1) << G1.pin_number) |
(((display_matrix[row][col] >> 2) & 0x1) << B1.pin_number));
LPC_GPIO2->PIN |= ((((display_matrix[row][col] >> 4) & 0x1) << R2.pin_number) |
(((display_matrix[row][col] >> 5) & 0x1) << G2.pin_number) |
(((display_matrix[row][col] >> 6) & 0x1) << B2.pin_number));
gpio__set(CLK);
gpio__reset(CLK);
}
}
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JOY STICKER
The JOY_STICKER is using the task to pool the ADC channel data to get the direction from the Joysticker.
- Loop through each time to poll the enum type data to get direction
- Receiving the data from two ADC channel(5=x, 4=y)
- Comparing which one has higher absolute data
- If (X > Y == YES) ,then we go to the loop to compare It's closer to Right or Left
- If (X > Y == YES && Right > LEFT == YES), then the status is Right
- If (X > Y == YES && Right > LEFT == NO), then the status is Left
- If (X > Y == NO) ,then we go to the loop to compare It's closer to Up or Down
- If (X > Y == NO && Up > Down == YES), then the status is Up
- If (X > Y == NO && Up > Down == NO), then the status is Down
System Flow Charts
System Testing and Validation
Technical Challenges
LED Matrix Flickering Issue
Issue: While we are developing the game, we notice that some color pixels are turned on when they are supposed to be off.
Investigation/Solution:
- See Known Breakout PCB Issues as a possible cause. It's possible the SJTWO board is getting inconsistent power.
- Refreshing the matrix should not be handled by an interrupt and not a task. The task should only push new display data and not have direct control of the matrix. Keeping the refresh interrupt driven would keep the refresh rate more consistent by removing the process being context switched out mid update.
MP3 Decoder - SJtwo Board SPI Selection
Issue:
- The mp3 decoder1053b's document is a kind of confusing for the mode when 1032b have several modes
- It's hard to know the configuration is successful or not.
Solution:
- Doing the survey on the GitHub is really important. For example, using the sin wave and hello binary example to test how the Initialization and HZ parameter would save a lot of time.
- Besides, we also have to be careful to check the SJBoard's SPI because of the SD card reader is using for reading SDcard. Hence, I would recommend using other
SPI0, SPI1 instead of using SPI2.
Conclusion
Conculsion please.
Video Demonstration
Source Code
Advice for Future Students
Source Control
Unless everyone in your group is comfortable using source control, don't use it. It will likely end up costing you time in the long run.
Test your LED Matrix and make sure it is not defective
The first 64x64 LED Matrix that we got from Sparkfun suffers from a serious flickering issue. After spending for a week trying to debug what causes the flickering issue, we still have no idea whether it is a hardware issue or software issue. Later, we borrow another LED matrix from a student of our class and test our code. With the other student's LED matrix (we use our own power supply and ribbon cables), there is no flickering issue at all. Therefore, we conclude that our LED matrix is defective.
