For our schematics, we originally started working with the L298N Dual H-Bridge/Full Bridge Motor Driver. As soon as we started trying to implement the H Bridge, we ran into a couple of issues. We discovered that we were using the L298N which was a 5V logic driven chip when we were only supplying 3.3V logic from the A3BU. To solve this issue, we switched to a different motor driver, the L293D. This driver was able to be driven using the 3.3V logic supplied by the A3BU. In order to do this, we were able to use inputs 1 and 2 to select the direction of the left motor and inputs 3 and 4 to select the direction of the right motor. This allowed us to have the motors run in a way that would allow the robot to turn left, right, forward, and backward.
As for the other schematic, we used the MAX232CPE USART Chip from our previous lab. This chip allows us to control the speed of our motors to allow our robot to run at different speeds. Our work for this chip wasn’t nearly as involved as the L293D because of the fact that we had already assembled it and had it working from a previous lab.
After we had the h-bridge working, we assembled all of our components into the chassis and had a working robot. We used an external battery to drive the motors to prevent us from ruining the board by having an over current issue. We used a 12V lipo (lithium polymer) battery in order to do this. We also used a portable battery pack with a 5V 3A output to power the A3BU and the Raspberry Pi.