Ezra Thomas' Pet on a Chip Reimplements a 1970s Robot Design on an FPGA — with Dramatic Improvements
Ditching discrete 7400-series logic chips for a custom SoC built on an FPGA, this robot outperforms its inspiration on every level.
Computer engineering student Ezra Thomas has blended old technology with new in the "Pet on a Chip" project — an effort to recreate a robot pet described in a 1979 book on a field-programmable gate array (FPGA).
"A few years back in high school I worked on building the robot described in the 1979 book 'How to Build Your Own Working Robot Pet' by Frank DaCosta," Thomas explains. "The robot was controlled by an 8085 (an 8-bit microprocessor), and required a ton of 74xx series logic chips to interface to the various control and sensor systems on the robot."
"For my senior design project in college, I wanted to create a new robot where all of the control logic would be integrated onto a single chip, and so Pet on a Chip was born."
The idea: To take the core design from DaCosta's book and reimplement it on an FPGA, instead of using discrete logic chips. Building on Thomas' earlier TinySoC project to create a simple FPGA-implemented system-on-chip, the result is a device which is considerably smaller, lighter, more efficient — and even more maneuverable.
"The robot’s FPGA contains the following modules," Thomas explains: "A custom 8-bit CPU with on-chip memory; A simple text mode VGA graphics controller; Twin closed loop motor speed controllers; A servo controller; An interface to a sonar module; A UART; Counter/Timers; GPIO [General Purpose Input/Output]."
Based on a custom eight-bit RISC architecture and running at 16MHz, the resulting robotics-centric SoC resides on a custom circuit board designed to be housed on a smaller version of the Robot Pet's chassis — constructed cheaply from three plywood plates.
"Pet on a Chip avoids obstacles more reliably than the original pet, it weighs almost 12 times less, and requires almost 13 times less power," Thomas concludes of the project's efficacy. "Additionally it is significantly more maneuverable with a turning radius of zero, and has a sonar range of over seven times the original."
The full project write-up is available on Thomas' blog, with source code and design files available on GitHub under the permissive MIT License.
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