Figure 1: Tetris Gaming Device v2 Breadboard Prototype
For the past month, I’ve been working on the second version of my Tetris Gaming Device. This first picture shows you almost everything I’ve included in this version except for the two 8×8 RGB LED matrices.
One major difference between this one and the first version I made last September is that I’ve replaced the 74HC595 shift registers with LED driver ICs. The problem with using 74HC595 shift registers to drive the led matrix is that they can’t supply enough current though each channel. An example would be when you having text scrolling across the screen, and you can clearly see the dimming in columns that have more LED lit up than the others. To solve this problem, I decided to replace the two column (anode) driving shift registers with a single MIC5891 source driver from Micrel, and the six row (cathode) shift registers with three STP16DP05 constant current LED sink drivers from STMicroelectronics. After making these changes, the brightness of each LED won’t change at all no matter how many of them light up in each column. Absolutely fantastic!
Figure 2: Tetris Gaming Device v2 PCB, ordered from Advanced Circuits (4pcb.com)
I’ve also added several other components to the system. First of all, I’ve added an accelerometer breakout board to provide a motion controlled gaming experience. The IC on this breakout board is the MMA8452Q from Freescale. It talks to the ATmega328 over I2c at 800Hz and provides 3-axis acceleration with either 12-bit or 8-bit resolution. Next, I’ve added a vibration motor to provide extra physical feedback to the player. In the current Arduino sketch, I’ve decided to let it vibrate whenever a line is cleared for about half a second. Last but not least, I’ve added a second LED bargraph to make the pcb look more symmetric. The two bargraphs are individually controlled by the 328 and can be used for any kind and status indication.
Figure 3: Populated PCB with LED Matrices removed, everything hand soldered
This is my first time designing a PCB, and I inevitably made a couple mistakes in the PCB layout. The first major issue is that the eagle part I used for the LED Matrix is from one of SeeedStudio’s PCB, and its dimension is short by 1mm on each side. As a result I had to bend the pins on the two matrices in opposite directions to make them fit together. In future PCB designs, I’ll definitely check the dimensions for any part from non-major manufactures. Second, I placed the female programming headers way too close to the bottom edge of the board. I actually wanted the headers to be flush with the bottom edge, but, for reasons unknown, I just didn’t bother to check the actual dimension of the headers.
Figure 4: The PCB in its final form running Tetris!
I’ve already designed an enclosure for this PCB in solidworks, and it will be 3D printed tomorrow. Since I have a midterm this Wednesday, I don’t know if I’ll have time to make a video of me playing it right after the enclosure is done. However, I’ll definitely be on this week’s Show and Tell at 7pm on Wednesday, so be sure to check out that video or watch it live!