An eye diagram visualizes signal integrity by overlaying many periods of a digital signal onto a single time window spanning 1-2 unit intervals (UI). The overlapping traces form a characteristic eye-shaped opening whose height, width, and clarity reveal signal quality metrics such as jitter, noise, and inter-symbol interference (ISI). A wide-open eye indicates clean signal transmission, while a closed or blurred eye signals degradation.
# anyplot.ai
# eye-diagram-basic: Signal Integrity Eye Diagram
# Library: makie 0.22.10 | Julia 1.11.9
# Quality: 90/100 | Created: 2026-06-18
using CairoMakie
using Colors
using Random
Random.seed!(42)
# --- Theme tokens ------------------------------------------------------------
const THEME = get(ENV, "ANYPLOT_THEME", "light")
const PAGE_BG = THEME == "light" ? colorant"#FAF8F1" : colorant"#1A1A17"
const ELEVATED_BG = THEME == "light" ? colorant"#FFFDF6" : colorant"#242420"
const INK = THEME == "light" ? colorant"#1A1A17" : colorant"#F0EFE8"
const INK_SOFT = THEME == "light" ? colorant"#4A4A44" : colorant"#B8B7B0"
const INK_MUTED = THEME == "light" ? colorant"#6B6A63" : colorant"#A8A79F"
# Imprint sequential colormap: brand green → blue (density)
const ANYPLOT_SEQ = cgrad([colorant"#009E73", colorant"#4467A3"])
# --- Simulation parameters --------------------------------------------------
const N_TRACES = 500 # overlaid NRZ bit periods (spec: 200–500)
const SAMPLES_PER_UI = 150 # time samples per unit interval
const JITTER_SIGMA = 0.03 # transition timing jitter (fraction of UI)
const NOISE_SIGMA = 0.05 # additive Gaussian noise amplitude (V)
const N_BINS_T = 300 # histogram bins along time axis
const N_BINS_V = 200 # histogram bins along voltage axis
const V_MIN = -0.30
const V_MAX = 1.30
const T_STEP = 2.0 / N_BINS_T
const V_STEP = (V_MAX - V_MIN) / N_BINS_V
# --- Data: generate NRZ eye diagram traces ----------------------------------
t_base = collect(range(0.0, 2.0, length = 2 * SAMPLES_PER_UI))
n_t = length(t_base)
all_t = Vector{Float64}(undef, N_TRACES * n_t)
all_v = Vector{Float64}(undef, N_TRACES * n_t)
for trace_idx in 1:N_TRACES
offset = (trace_idx - 1) * n_t
# 4 random NRZ bits: [pre-window, bit0, bit1, post-window]
bits = rand(Bool, 4)
# Build waveform: start from bits[1] level
v = fill(Float64(bits[1]), n_t)
# Accumulate bandwidth-limited sigmoid transitions at t = 0, 1, 2 UI
for b in 2:4
if bits[b] != bits[b - 1]
delta = Float64(bits[b]) - Float64(bits[b - 1])
t_trans = Float64(b - 2) + randn() * JITTER_SIGMA
@. v += delta / (1.0 + exp(-25.0 * (t_base - t_trans)))
end
end
# Additive Gaussian noise
v .+= randn(n_t) .* NOISE_SIGMA
all_t[(offset + 1):(offset + n_t)] .= t_base
all_v[(offset + 1):(offset + n_t)] = v
end
# --- 2D density histogram ---------------------------------------------------
t_centers = collect(range(T_STEP / 2, 2.0 - T_STEP / 2, length = N_BINS_T))
v_centers = collect(range(V_MIN + V_STEP / 2, V_MAX - V_STEP / 2, length = N_BINS_V))
density = zeros(Int, N_BINS_T, N_BINS_V)
for i in eachindex(all_t)
ti = clamp(floor(Int, all_t[i] / T_STEP) + 1, 1, N_BINS_T)
vi = clamp(floor(Int, (all_v[i] - V_MIN) / V_STEP) + 1, 1, N_BINS_V)
density[ti, vi] += 1
end
# Log-scale density; empty cells → NaN (renders as background in heatmap)
density_log = [density[i, j] > 0 ? log1p(Float64(density[i, j])) : NaN
for i in 1:N_BINS_T, j in 1:N_BINS_V]
# --- Plot -------------------------------------------------------------------
const TITLE_STR = "eye-diagram-basic · julia · makie · anyplot.ai"
const TITLE_SIZE = max(16, round(Int, 20 * 67 / length(TITLE_STR)))
fig = Figure(
size = (1600, 900),
fontsize = 14,
backgroundcolor = PAGE_BG,
)
ax = Axis(
fig[1, 1];
title = TITLE_STR,
titlesize = TITLE_SIZE,
titlecolor = INK,
xlabel = "Time (UI)",
ylabel = "Voltage (V)",
xlabelsize = 14,
ylabelsize = 14,
xlabelcolor = INK,
ylabelcolor = INK,
xticklabelsize = 12,
yticklabelsize = 12,
xticklabelcolor = INK_SOFT,
yticklabelcolor = INK_SOFT,
xtickcolor = INK_SOFT,
ytickcolor = INK_SOFT,
backgroundcolor = PAGE_BG,
topspinevisible = false,
rightspinevisible = false,
leftspinecolor = INK_SOFT,
bottomspinecolor = INK_SOFT,
xgridcolor = RGBAf(INK.r, INK.g, INK.b, 0.12),
ygridcolor = RGBAf(INK.r, INK.g, INK.b, 0.12),
xminorgridvisible = false,
yminorgridvisible = false,
xticks = [0.0, 0.5, 1.0, 1.5, 2.0],
yticks = [0.0, 0.5, 1.0],
)
hm = heatmap!(ax, t_centers, v_centers, density_log;
colormap = ANYPLOT_SEQ,
nan_color = PAGE_BG,
)
# Eye opening reference lines (spec: "Optionally annotate eye height and eye width")
const ANNOT_COLOR = RGBAf(INK_SOFT.r, INK_SOFT.g, INK_SOFT.b, 0.65)
# Eye height: 20% and 80% voltage boundaries (NRZ: 0–1 V amplitude)
hlines!(ax, [0.20, 0.80];
color = ANNOT_COLOR,
linewidth = 1.5,
linestyle = :dash,
)
# Eye width: center of each eye opening at 0.5 and 1.5 UI
vlines!(ax, [0.5, 1.5];
color = ANNOT_COLOR,
linewidth = 1.5,
linestyle = :dash,
)
text!(ax, 0.52, 0.82; text = "Eye height: 0.60 V", color = INK_MUTED,
fontsize = 10, align = (:left, :bottom))
text!(ax, 1.52, -0.24; text = "Eye width", color = INK_MUTED,
fontsize = 10, align = (:left, :bottom))
Colorbar(fig[1, 2], hm;
label = "Trace Density (log scale)",
labelsize = 12,
ticklabelsize = 10,
labelcolor = INK,
ticklabelcolor = INK_SOFT,
tickcolor = INK_SOFT,
width = 18,
)
xlims!(ax, 0.0, 2.0)
ylims!(ax, V_MIN, V_MAX)
colsize!(fig.layout, 1, Relative(0.90))
# --- Save -------------------------------------------------------------------
save("plot-$(THEME).png", fig; px_per_unit = 2)
Part of Signal Integrity Eye Diagram on anyplot.ai.