Mouser PSoC6-WiFi-BT L4 : The Video Game

Designing low-power, cloud-connected IoT devices with PSoC® 6 MCU’s and WICED® Wi-Fi/Bluetooth

Summary

In this lesson I’ll finish the video game thread by adding the graphics etc. to play the game.  In addition I’ll fix up the CapSense thread so that it is connected to the game via an RTOS queue.

There are three main things going on in this game.

  1. A state machine for the game screen (Splash, Start, Running, Over)
  2. A 20ms timer that updates the screen while the game is running (moves the Paddle and the Ball)
  3. A GUI queue where the rest of the system – CapSense,  Bluetooth and WiFi – can send Button and Paddle messages.

To implement this project I will:

  1. Setup the project and makefile by copying L3CapSenseTft
  2. Update gamethread.h to define the GUI queue messages
  3. Fix main.c to create the queue
  4. Create SystemGlobal.h to give the rest of the files access to the gui queue
  5. Updating the CapSenseThread to send GUI messages
  6. Update the includes in GameThread.c
  7. Add some #define macros to define game parameters
  8. Add a State Machine for the game & define some paddle movement methods
  9. Make forward declarations for the thread functions
  10. Create some variables to maintain game state
  11. Add display functions for the score and the speed
  12. Add functions to start and end the game
  13. Add helper functions to calculate the top and bottom of the paddle
  14. Add a function to update and draw the paddle
  15. Add a function to update and draw the ball
  16. Add a function for the game timer to call
  17. Update the main game thread

Setup the project and makefile by copying L3CapSenseTft

Use copy/paste to copy the L3CapSenseTft project to a new folder name L4Game.   Change the name of the makefile to be L4Game.mk.

Edit the makefile and change the name of the application.

Create a make target for this project

Update GameThread.h to Define the GUI Messages

All of the threads in the system (CapSense, Bluetooth, and WiFi) will control the paddle and the button by sending messages to an RTOS queue.  In gameThread.h we will add a definition of that message.  The message is just a structure with two values – which GUI element and what value to send.

Fix main.c to Create the Queue

I typically believe that the RTOS primitives should be owned by the main.c.  To do this edit main.c and fix the includes.

Then define the queue variable “paddleQueue” which I should have names “guiQueue” but it is way to late to fix it now — oh well.

Create the queue

Create SystemGlobal.h

Each of the threads in the system need to have access to the paddleQueue.  In order to do that create a file called SystemGlobal.h and extern the variable to give them that access.

Updating the CapSenseThread to send GUI messages

Remember that when we setup the CapSenseThread originally, it just printed out the values.  Let’s fix it so send messages.  So, edit CapSenseThread.c.

  1. Add a message variable (line 8)
  2. Fix the button0 and button 1 to make and send RTOS messages (lines 20/21 and 26/27)
  3. Fix the slider to send the position (lines 33-35)

Update the includes in GameThread.c

Now let’s fix GameThread.c.  Start by editing the includes to add a new file called “SystemGlobal.h” which contains the global variable for the GUI queue.

Add some #define macros in GameThread.c

There are a number of constants which I use in the game.  In this section I use #define macros to define them.

Add a State Machine for the Game & Define Paddle Movement

Open up GameThread.c – all of the game control functions will go there.

There will be four screens in the game.  A splash screen to display Cypress and Mouser, a Ready Player 1 Screen, the actual game screen and a game over screen.

In addition the paddle can move a little bit at a time (increment) or jump directly to the position (absolute)

Fix the gameState statemachine

In the splash screen I need to set the state machine to GS_SPLASH

In the start screen I need to set the state machine to GS_START

Make Forward Declarations for Functions

You should define the functions in advance of using them

Create some variables to maintain game state

The updateScreenTimer is used while the game is running to call the updateScreen every 20ms.  The rest of the variables are self explanatory.

Add Display Functions for the Score & Speed

These two functions print the speed and score at the top of the screen.

Add Function to Start the Game

When the game needs to start you:

  1. Reset the score
  2. Set the paddle position
  3. Move the ball to the middle of the paddle
  4. Set the ball to move to the right and down
  5. Clear the screen, display score and speed
  6. Start the game running

Add Function to End the Game

When the game is over you should:

  1. Move the game state to over
  2. Stop the timer
  3. Display game over
  4. Display press button 0 to start

Add Helper Functions to Calculate Paddle Top & Bottom

There are two places where you need to know the position of the Paddle.  Specifically:

  1. To draw the paddle
  2. To figure out if the ball hit the paddle or not.

These two functions calculate the pixel position of the top and bottom of the paddle based on it current position

Add a Function to Update & Draw the Paddle

While the game is running you need the paddle to move.  There are two methods:

  1. Absolute just moves the current position immediately to the desired position.
  2. Incremental, which moves the paddle a little bit towards the desired position.

Add a function to update and draw the ball

You need a function to:

  1. Move the ball
  2. Figure out if it hit the right/left/top/bottom of the screen and do the right thing.

When the ball hits one of those surfaces it needs to change direction to either plus or minus.

Every time it hits the paddle the score should increase and possibly speed up.

If it misses the paddle the game is over.

Create a Function for the Game Timer

An RTOS timer runs every 20ms.  That timer needs a function to move the paddle and move the ball.

Update the Main Game Thread

The main game thread needs to get messages out of the queue and then do the right thing based on the game state.

Program and Test

Now that it is all done… program and test it.

GameThread.c

Here is the whole thread is here so you can copy/paste it into your file.