DE10-Lite Digital Oscilloscope

A real-time digital oscilloscope implemented on the DE10-Lite development board using a RISC-V soft processor and external AD7705 16-bit ADC.

Overview

This project implements a functional oscilloscope that:

• Samples analog signals (0-3.3V) via an external AD7705 sigma-delta ADC
• Displays real-time waveforms on a VGA monitor (320×240, 8-bit color)
• Provides user controls for gain, sample rate, pause, and freeze functions
• Shows live measurements on both VGA display and 7-segment displays
• Added a BNC connector so you can hook up actual oscilloscope probes, and a potentiometer for testing.

Demo

Hardware Setup

*DE10-Lite board connected to AD7705 ADC module with BNC connectors and potentiometer for testing*

Waveform Display

Gain 1x, 150 Hz	Gain 4x, 150 Hz	Gain 1x, 350 Hz

Signal Acquisition

• ADC: AD7705 16-bit sigma-delta converter
• Interface: Bit-banged SPI Mode 3 (CPOL=1, CPHA=1)
• Sample Rate: Adjustable 50-500 Hz
• Gain: Selectable 1×, 2×, 4×, 8×
• Voltage Range: 0-3.3V (unipolar mode)

Display

• VGA Output: 320×240 pixels, RGB332 color encoding
• Waveform: Orange trace with sweep-style update
• Grid: Dashed grid lines
• Info Display: Current voltage, min/max, gain, sample rate
• 7-Segment: Real-time voltage and gain readout

Controls

Switch/Button	What it does
Button	Pause/Resume
SW0	Freeze the screen
SW2	Gain = 2×
SW3	Gain = 4×
SW4	Gain = 8×
SW8	Slower sample rate (-50 Hz)
SW9	Faster sample rate (+50 Hz)

Hardware

• DTEK-V RISC-V: Terasic DE10-Lite with DTEK-V RISC-V soft processor
• ADC: AD7705 adc board
• Display: VGA monitor
• Power: 3.3V power for the ADC
• potentiometer: Potentiometer (optional, for testing voltage changes)
• BNC: BNC to screw terminal adapter (optional, for oscilloscope probes)

Wiring

DE10-Lite GPIO    AD7705
─────────────────────────
GPIO[0]    ───►   CS (Chip Select)
GPIO[1]    ───►   SCLK (SPI Clock)
GPIO[2]    ───►   DIN (MOSI)
GPIO[3]    ◄───   DOUT (MISO)
GPIO[4]    ◄───   DRDY (Data Ready)
GPIO[5]    ───►   RESET
3.3V       ───►   VCC, REF+
GND        ───►   GND, REF-

Project Structure

src/
├── main.c                       # Main loop
├── ad7705_driver.c/.h           # ADC communication
├── spi_driver.c/.h              # SPI bit-banging
├── vga_driver.c/.h              # Drawing stuff on screen
├── vga_text.c                   # Text/font rendering
├── timer.c/.h                   # Timer for consistent sampling
├── hardware.c/.h                # Switches, LEDs, 7-segment
├── delay.c/.h                   # Delay functions
├── performance_counter.S        # Performance counter assembly 
├── performance_counter.h        # Performance counter header 
├── performance_counter_prints.c # Print counters function 
├── boot.S                       # Startup code
├── dtekv-lib.c/.h               # DTEK-V library
├── dtekv-script.lds             # Linker script
└── Makefile                     # Build file (modified for -O0/-O3)

How to Build and Run

Prerequisites

• RISC-V toolchain (riscv32-unknown-elf-gcc)
• MCB32tools

Compile

cd src
make

Run

jtagd --user-start
dtekv-run main.bin

If it doesn't start, try:

killall jtagd
jtagd --user-start
dtekv-run main.bin

Clean

make clean

Advanced Project - Performance Analysis

This project includes a performance analysis component using DTEK-V hardware performance counters.

Compile with Different Optimizations

# No optimization
make build-O0

# Heavy optimization
make build-O3

This creates main-O0.bin or main-O3.bin

Run Performance Test

dtekv-run main-O0.bin   # or main-O3.bin

Wait for 500 samples (~3-4 seconds), and counter values will be printed to the terminal.

You can change the number of samples by editing PERF_TEST_SAMPLES in main.c.

Some Technical Notes

SPI

Since DTEK-V doesn't have hardware SPI, we had to bit-bang it ourselves. It runs at about 1 MHz and uses Mode 3 (clock idles high, sample on rising edge). The ADC does self-calibration when it starts up and whenever you change the gain.

VGA

The frame buffer sits at 0x08000000. We use Bresenham's algorithm for drawing lines and a column-erase approach so the display doesn't flicker when updating.

Calibration

There's a calibration factor (around 1.535) in the ADC driver to account for the voltage divider and component tolerances. If your readings are off, you might need to tweak this value in ad7705_driver.c. The voltage reading includes a calibration factor (1.535×) to compensate for:

• Input voltage divider effects
• ADC reference voltage tolerance
• Component variations

Course Information

Developed for IS1200 HT25 Datorteknik at KTH Royal Institute of Technology.

License

This project is under a proprietary license.

• COPYING for license information.
• LICENSE

Authors

• Sana Monhaseri

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DE10-Lite Oscilloscope - IS1200 Project 2025 - TcomK