The 0x0604 wire "level" is a gain-step index 0..N-1, not a 0-100
percent. G HUB reads the step count N from getSidetoneLevelSettings
(function 2) and scales: level = (N-1)*pct/100. Solaar wrote the raw
percent, which only matches when N == 101 — so V2 headsets reporting a
smaller N (G522: N=10) got out-of-range step writes the firmware
silently ACK'd without applying.
Read func 2 at build time, take reply byte 2 as N (default 101 when
the call is absent — V1 — or the reply is unusable). The validator now
maps the 0-100 UI percent to/from the wire step index and clamps
writes to N-1. V1 devices (e.g. PRO X 2) keep N=101, which makes the
scaling an exact identity — their wire traffic is unchanged. The raw
func-2 reply is still logged at debug level for a future G HUB
setpoint correlation.
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