Multi-File Comparison

This tutorial shows how to load and compare signals from multiple waveform files in NovyWave. We’ll use test files from the NovyWave repository, but you can follow along with any waveform files.

Step 1: Load Multiple Files

1. Click Load Files
2. Navigate to the test_files/ directory
3. Check the boxes next to simple.vcd and simple_reload_test.vcd
4. Click Load

Both files now appear in the Files & Scopes panel.

You can also load files one at a time — click Load Files, select a file, load it, then repeat for the next file.

Step 2: Understand File Disambiguation

If files have the same name from different directories, NovyWave adds path prefixes:

tests/pass/design.vcd  →  pass/design.vcd
tests/fail/design.vcd  →  fail/design.vcd

Hover over a signal name in the Selected Variables panel to see its full path, scope, and signal type.

Step 3: Select Signals from Multiple Files

From the First File

1. Expand simple.vcd > simple_tb > s
2. Click the checkbox next to s
3. In the Variables panel, click A and B

From the Second File

1. Expand simple_reload_test.vcd > simple_tb > s
2. Click the checkbox next to s
3. In the Variables panel, click A and B

Step 4: View Combined Signals

The Selected Variables panel shows signals from both files together on the same timeline.

Step 5: Time Alignment

Both files start at time 0, so they align automatically.

Press R to see the full combined timeline. The view extends to cover the longest file.

If your files have different durations, signals from the shorter file show N/A outside their time range.

Step 6: Compare Signals

Visual Comparison

Look for differences in waveform patterns. Mismatches stand out when signals are adjacent.

Cursor-Based Comparison

1. Press R to see the full timeline
2. Click on an area that looks different
3. Use Q/E to fine-tune cursor position
4. Compare values in the Value column

Jump to Differences

Use Shift+Q and Shift+E to jump between transitions. If the files differ, one signal will transition while the other doesn’t.

Practical Tips

• Press Z to recenter the green zoom line around time 0
• Press R to fit the whole combined range
• Compare related signals in the same format to reduce visual noise
• Add clock signals from both files to verify time alignment
• Compare output signals first — trace backward from differences to find the root cause

Common Use Cases

Regression Testing

Compare known-good waveforms against current results:

test_pass.fst      # Reference
test_current.fst   # Under test

Mixed Language

Combine Verilog and VHDL simulation outputs:

verilog_top.vcd    # Verilog wrapper
vhdl_core.ghw      # VHDL implementation

Removing Files

• Click X on individual files in the Files & Scopes panel
• Or click Remove All to clear everything

Persistence

NovyWave automatically saves your multi-file setup — loaded files, selected signals, and view settings persist across sessions.