Hobby Servo SCOMP Peripheral

FPGA Peripheral and Assembly Driver

A memory-mapped servo pulse generator for the SCOMP soft CPU on a DE10-Standard, plus the assembly program that drives it.

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Concept diagram: a binary angle on the switches, 1011010 for 90 degrees, goes into the servo peripheral, which turns the servo horn to that angle — fig.01 · photograph

kind: project
course: ECE 2031, Georgia Tech
category: embedded
period: Aug 2023 - Dec 2023
status: completed
role: Project manager and lead assembly author
team: 5 members

head -n 20 README

A hobby-servo peripheral in VHDL for SCOMP, a 16-bit soft processor on a Terasic DE10-Standard, and the assembly program that drives it. The final project of a nine-lab digital design sequence.

The peripheral is a pulse generator mapped into SCOMP's I/O space. A write latches a command; the hardware masks the angle, clamps it at 180 degrees and turns it into a servo pulse between 0.5 and 2.5 ms, refreshed on a 20 ms frame from a 10 kHz tick with a counter that steps by nine. The command is 10 bits: two for an advanced mode, seven for the angle, and a last bit that switches application. I was the project manager and led the assembly side; the team was split into VHDL, assembly and management, with a schedule to track progress. Besides the angle controller, the peripheral supports switching modes without a reset, implemented as a small state machine on the lowest command bit.

grep -n highlights

01Project manager and lead assembly author on a five-person team.
02Built a servo pulse-generator peripheral mapped into SCOMP's I/O space, clamping the angle in hardware and generating 0.5 to 2.5 ms pulses on a 20 ms frame.
03Led the assembly side: a test program that passes switch values straight to the peripheral, and the mode-switching flow on the lowest command bit.
04Defined the 10-bit command format and the mode-switching flow.
05Worked up to the project through a nine-lab sequence, including adding SUB and JPOS instructions to the SCOMP CPU in VHDL.

ls ./media

Table of the 10-bit command: two bits for the advanced mode, seven bits of pulse angle, and a last bit that switches application — fig.02The 10-bit command: two mode bits, seven bits of angle, and the application-switch bit.

Flowchart of switching applications: write 1 to enter the advanced mode, 0 to confirm, use the top two bits, write 0 to leave — fig.03How a program switches modes without a reset, driven by the lowest command bit.