The square was the mock's only ideal step, which is the one shape a real producer
does not put on the wire. It is now the truncated Fourier series of the step --
`--square-harmonics N` odd harmonics, default 30 -- so each edge overshoots by the
Gibbs constant (about 9% of the 2 V swing, y = +/-1.179) and then rings, and
`--square-harmonics 0` is the ideal +/-1 step as before.
Odd harmonics only, so the series keeps the ideal wave's edge instants and its
polarity: the level-0 trigger, the glitch's inverted pulse and the buffer search
land where they did. Re-run in pairs (`--square-harmonics 0` against the default),
search, condition legs 0/1, trigrenum, disarm, trig trace, measures and events all
read exactly what they read before, with only `t0` moving. The reading that moved
is the noise probe's group-delay leg, whose `want` is the analytic `tau*ln2` of a
step: a band-limited edge reads `delay=0.002770 ratio=1.255`, the same figure on
every run. That recipe now asks for the ideal step, so its documented number stays
exact; probe-readings says why.
The series is vectorised: as a per-sample Python sum it cost ~15 sin() calls a
sample, which at the fast mock's 1.3 MS/s made the producer the bottleneck and
halved the rate the app saw (the noise probe's span-dependent counts read 22
against 48). Vectorised it adds ~0.5 ms to a 2000-sample packet, so the fast mock
runs at about nine tenths of its declared pace and those counts read within a few
percent.
Martino Ferrari
afd2a6cdc1