Pinball: The Eagle Schematic

In the last bunch of posts I have talked about the main systems of the pinball machine electronics package.  Now it is time to assemble all of those pieces into a complete system on an Eagle schematic which you can find in the “eagle” directory on the github site.

I use the multipage capability of Eagle to partition the schematic into 7 pages.

1. Main Page
2. LEDs
3. Switches
4. Accelerometer
5. Power
6. Motors
7. Test Points

The main page contains the

1. PSoCBLE module:  Notice that I used every single pin except for VRef.  Also notice that I overloaded SWD-Clock and SWD-IO pins by attaching capsense buttons to those pins.  This means that I will never be able to debug and use Capsense at the same time.
2. USB Connector:  When I was trying to figure out how to make the board less expensive my son suggested that everybody has a USB charger, so why don’t you just power the pinball machine with that?  I thought that this was a great idea as it eliminates a $5+ wall wart.
3. Two buzzers.  These are super simple low cost 12mm through hole buzzers which are used by the MusicPlayer component.
4. Two capsense buttons multiplexed to the SWDCLK and SWDIO pins of the chip.  Notice that they have a 560Ohm series resistor
5. The reset button for the system which just pulls down the XRES when you press the button.  It also has the 10K pullup resistor which pulls up XRES when the button is not being pressed
6. Pull-up resistors for the 5V I2C bus.
7. A 5-Pin programming plug for the MiniProg-3 connected to SWDIO and SWDCLK and the Power/Ground
8. A plug for the I2C LCD to connect to the I2C Bus

Page two of the schematic contains two connectors for the LEDs which I talked about in detail in the Matrix LED Posts .  It also contains the current limiting resistors.  In order to save money in the BOM I am not going to actually put connectors into the 100mil center holes, but will let the kids learn to solder by attaching the wires directly into the holes with solder.

Page three of the schematic contains the switch matrix connectors and diodes.

I thought that it would be a really cool idea to have an accelerometer on the board to provide a tilt functionality.  This actually turned out to be a serious PITA because I couldn’t find a cheap accelerometer that was 5v.  So, in addition to the accelerometer I have to provide a level translator for the I2C bus (PCA9306) and a level translator for the Accelerometer interrupt line (the mostfet and pull-up resistors).  I also have to provide a 3.3v power supply (next page of the schematic)

The 3.3v accelerometer requires a 3.3v power supply, so on this page I use an REG317 to create 3.3v from the VBUS power supply.

In order to drive the two brushed DC motors I use a TB6621 motor driver chip that contains two H-Bridges.

Finally I like to have test points on the board to measure stuff while I am assembling the board.

In the next post Ill talk about the creation of the layout for the printed circuit board.

You can find all of the source code and files at the IOTEXPERT site on github.