The idea behind making our family units come alive is making them play the programming we want when we want. Then when an observer walks by and sees the mother playing programming appropriate for her but different from her children, whose programming is appropriate for them, they will get the picture that the bigger t.v. showing adult programming must be an adult unit. And the smaller t.v.'s showing children's programming must be children units. Hey, this must be some sort of family!! Bad-a-bing! our artistic idea birthed through technological means.
Back to the technology. Our basic idea is to bypass the buttons on the DVD players with transistors that are controlled by a microcontroller supplied through our instructor, called LogoChip. The microcontroller is capable of storing a program that we can specify and executing it upon a specified trigger, which is conveniently controlled through a button-type switch. I'll go more in-depth later, but for now the important concept is that we want to program our chip to tell the DVD player to power on, play, hard stop (reset to the beginning of the DVD), and fast-forward through chapters as fitting to the programming Joey edits.
To begin the fun, we took apart the DVD player. (We are using two CyberHome DVD players. They are cheap, simple, and using two identical players should means we only have to do this process once.)
Since the parts of interest are the buttons on the front of the player, we then remove the plastic face to reveal the circuit board. As you see, the buttons on the front of the player are plastic pieces that in turn push on button-style switches on the circuit board.
Flipping the circuit board over, we find what we are looking for, the electrical contacts to which we will solder lead wires which will be connected to our transistors. (Yes, I know these pictures are post-solder, but you'll just have to use your imagination.)
Next, to know which contacts to which to solder, we look closely at the front of the circuit board.
Here we find a pin-out legend for the group of wires running from the circuit board to the rest of the DVD player. The pin-out legend reads:
(1.) PWR +5V (2.) GND (3.) INFRARED (4.) LED (5.) GPIO 0 (6.) GPIO 1 (7.) GPIO 2 (8.) GPIO 3 (9.) GPIO 4
With this knowledge, we turn the circuit board over and trace the metal inlay paths to see which contacts of the switches do what. We see that the button-style switches have four contacts, but we know that they are actually two contacts, connected vertically inside the switch. We also see that the eject, forward, and rewind switches have a common connection. Likewise with play, stop, and on/off, though it is NOT the same shared connection as the former three. Another observation is the right sides of the switches are connected to the right sides of the switches either above or below them. (looking at the board through my picture) Considering all this, we can draw the second diagram below, and with deductive reasoning, we can draw the third, giving us the specific contacts we need to solder into.
One thing I forgot to mention is we ran a voltage test to further investigate what was going on when the switches were open and closed. The bottom three switches showed a voltage of 2V open, and 0V closed. Makes sense. This is how we reasoned that the left side of the bottom switches were the same contact as Pin (1.), with the exception of a couple resistors. The interesting finding was the top three switches showed opposite results: 0V open, 2V closed. This caused us problems later when we tried to interface the DVD players with the LogoChip.
You may ask why go through this mapping out of the circuit board and deductive reasoning; why not simply assign one terminal of each transistor for each terminal of each switch? Two answers: 1. we got lost in the fun of figuring out how they worked, and 2. if we did that, we would have to solder 8 wires onto the circuit board for the 4 switches we're going to use. We like being efficient, and we like only soldering the deduced 5 wires instead of 8. When it came to soldering onto the board, the solder didn't want to adhere to the contacts. We had to really heat them up first. Also, the pictures here are pretty close to life size. It wasn't easy. We then soldered our wires onto the contacts of the board and proceeded to interface them with the LogoChip.
