Difference between revisions of "F21: Juvenile Jumpers"

PCB Top View

LED MATRIX

A 64x64 RGB LED Matrix is used as a display. The LED matrix panel has 4096 RGB LEDs. Each LED can be controlled independently. LED Matrix uses only 13 digital GPIOs to fully control each LED. This 64x64 LED matrix has six 64-bit shift registers for R1, G1, B1 R2, G2, B2 where each color of the LED is controlled by one bit of the shift register. The LED matrix displays three main colors like RED, BLUE, GREEN. By combing these three colors we can make different colors like YELLOW, CYAN, PINK, WHITE, Magenta.

Start Screen

RGB LED Matrix

Dual Axis Joystick

This project uses the joystick to control the movements of the jumper. This project uses x-axis values to move the jumper to the left and right sides. A switch on the joystick is used to start the game by pressing the switch. The joystick provides the analog output, therefore the joystick is connected to ADC pins of the SJTwo board. It is operated on a 5V power supply.

Dual Axis Joystick

MP3 Decoder

MP3 Decoder

Hardware Interface

Software Design

This game has two levels. Following is the overview of a game play.

Game Overview

1. Level_1:

• In the first level, the jumper needs to jump on the tiles. Some tiles have an additional spring and if the jumper lands on the spring, the jumper will jump much higher than it generally would on landing on the standard tiles.
• With each jump to the next level the score gets incremented by 10 and appropriate music is played
• After jumping on the next level the background screen and the jumper are shifted down to the bottom most position
• The jumper again starts to jump from this position
• If while coming down, the jumper is not able to find a tile to land on the game is finished
• If the score is more than 150 then the second level will begin.

2. Level_2:

• This level adds some difficulty to the game. This level move adds enemies to the game.
• Jumper has a gun functionality. By using a gun jumper can kill the enemy.
• If the jumper collides with the enemy game will be over.
• Rest all stays like Level 1

There is a total of five tasks involved in this game in order to ensure full functionality.

Task Hierarchy

1. Start and stop task:

• This task displays the game's start screen. To start the game player need to press the onboard switch on the joystick.
• After the game is finished, if the player presses the button again, the game would start again. This is also handled by this task.

2. Background task:

• This task creates background tiles for the jumper to jump on.
• It keeps on refreshing the led_matrix frame buffer with background data buffer.

3. Game logic task:

• When the game starts this task detects the jumper's initial position and starts jumping up.
• Jumper will start going down after reaching a certain height.
• It checks for the collision with tiles. If a collision is not detected then the jumper will keep going down.
• If a collision is detected then it shifts the background screen and jumpers down.
• It will update the score and check the level.
• If the score is more than 150, it will start level 2 of the game.

4 LED Matrix task:

• This task keeps displaying frame data every 1ms.
• This is a high-priority task.

5 Enemy tasks:

• This task creates enemies at a random position.
• It moves enemies from column 0 to 63

6 Gun Task:

• This task keeps on monitoring the joystick data for Y-axis
• If this task detects a y-axis value greater than 4000, a gun will be shot.

Implementation

LED Driver

A 64*64 led matrix is used for this project. The led matrix is divided into two halves of 32*64 each. It has 3 R,G,B pins and 3 64-bits registers (shift registers) for each upper and lower halves. The address lines provided are 5. This means that at a time same row from the upper half and the lower half will be selected. So in order to display a particular row appropriate row should be selected and appropriate data needs to be fed to the RGB shift registers of both top and bottom halves. LED matrix is initialized by configuring the required pins as output. The led matrix has 3 more pins enable which are essential to display a pixel on the matrix. The clk pin that should used as a clk to the shift registers to shift the data out, the latch pin is used to latch the data from the shift registers onto the matrix's buffer, the output enable pin that is used to display the latched data on the selected row.

• Before feeding matrix data disable Output Enable (OE) GPIO
• Set bits on A, B, C, D GPIO pins to select the particular row.
• Loop through the pixels (columns) in the selected row and set the pixel color on R, G, B GPIO pins
• To mask that particular pixel set zero on R, G, B GPIO pins
• Set and Reset the clock for pushing the R, G, B bits for each column
• Issue latch to mark the row's completion
• Set OE
• Small delay
• Reset latch before going to next row

MP3 Decoder

• mp3 music changes according to the state of the game.
• To get the game state sound flags are checked.
• Music is placed in the file so need to find the respective file.
• Open the mp3 file.
• Read the contents of the file.

Code snippet for MP3:

void mp3_play_sound(int num) { mp3__send_command(PLAY_FILE_WITH_FOLDER, 0x01, num); }

void mp3_play_jump_up_sound() {
  mp3_play_sound(2);
  vTaskDelay(50);
}

Joystick

• Initialized the ADC Peripheral
• Set the appropriate pin functionality using the IOCON registers.
• Set the ADC pin functionality as input.
• Select ADC channels to read.
• Enable burst mode for a fast conversion.

Code snippet for Joystick:

void initialize_joystick() {
  enable_joystick(GPIO__PORT_0, 25, GPIO__PORT_1, 30, GPIO__PORT_1, 31);
  button_press = p1;
}

Testing & Technical Challenges

PCB Design

We struggled to get the dimensions of the power supply module to design the PCB as the exact module was not available in the library. We have selected the pin dimensions for the power supply module by referencing other pin headers and using a general approximation to make it work satisfactorily. Because of this, the PCB went through a lot of internal revisions. While testing hardware on the PCB for the first time we faced a problem related to ribbon cable. To solve this problem we just replace the ribbon cable but we spent too much time realizing the problem.

LED Matrix

1. Collision detection with tiles not working after the 32nd column. This is due to the variable was not typed cast to uint64_t.

2. The random number generator generates the same pattern and hence the tiles. Seeding just once with xTaskGetTickCount() did not generate randomness.

3. Led buffer overwrite due to collision leaves background screen in an inconsistent state. To resolve this issue keep refreshing the background screen in a task.

Conclusion

We successfully designed the Juvenile Jumper game using the RGB LED Matrix and the SJ2 board. Implementing this project from scratch gave us more practical exposure in developing real-time embedded applications. This project helped us to better understand all the FreeRTOS APIs and their functioning. We learned about PCB design and various driver implementation.

Project Video

• Juvenile Jumpers - video

Project Source Code

• Gitlab link

References

Acknowledgement

We would like to sincerely thank Professor Preetpal Kang for designing such a fantastic course and for his continuous guidance and support throughout the implementation of this project. Further, we would like to thank the ISA team for their advice.

References Used

• FreeRTOS APIs
• Sparkfun Eagle Software Tutorial
• LED matrix Driver Guide
• MP3 Decoder Datasheet