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Revert F3/F4 auto-channel NACK (misread probe) #3

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Merged
VU3ESV merged 1 commit into from
May 23, 2026
Merged

Revert F3/F4 auto-channel NACK (misread probe) #3

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30 changes: 20 additions & 10 deletions CLAUDE.md
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Expand Up @@ -108,16 +108,26 @@ The VM also cycles `'1'`–`'5'` to retrieve scope/spectrum sample buffers
into bytes 40..63 of the response. v1 ignores those modes; the on-meter
LCD is the only display.

**Firmware quirk — per-channel verbs in auto-channel mode:** `range_step`
(F3) and `alarm_toggle` (F4) are per-channel settings. When the meter is
in auto-channel mode (IN byte 4 == 0), the firmware silently ignores
these presses — there is no single "current channel" to mutate. The hub
intercepts these in `lpmeter.VerbAvailableInState` and NACKs with a
reason instead of writing a guaranteed-no-op OUT report; clients should
prompt the user to `channel_step` to a manual channel (CH1–4) first.
Confirmed empirically on 2026-05-09 by sending each verb 5× in auto-ch
mode and observing no change to offsets 6 / 7. `mode_step`, `channel_step`,
`peak_toggle`, `setup`, `freeze` all work in auto-ch.
**Per-channel verbs in auto-channel mode (NOT a firmware quirk —
correcting an earlier misdiagnosis):** `range_step` (F3) and
`alarm_toggle` (F4) are per-channel settings. Each of CH1..CH4
remembers its own range and alarm-enabled state. In auto-channel
mode, F3/F4 on the meter's front panel mutate the **auto-locked
channel's** setting — i.e. whichever channel auto-detection
currently has the signal locked to.

An earlier probe (2026-05-09) sent 6 `range_step` writes in auto-
channel and saw the *displayed* range stay at 2.5K, which was read
as "F3 is a no-op in auto-channel mode" and a server-side NACK
was added. That observation was misleading: each press DID step
the auto-locked channel's range, but auto-channel kept re-locking
to a different channel between presses, and the displayed range
is always whichever channel is currently locked. Confirmed wrong
on the bench 2026-05-16 by VU2CPL — pressing F3 on the meter in
pwr/swr + auto-channel does visibly cycle the range.

The NACK has been removed; `VerbAvailableInState` is kept as a
hook in case a real per-state firmware quirk surfaces later.

### IN-report decode

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52 changes: 26 additions & 26 deletions internal/lpmeter/decode.go
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Expand Up @@ -59,19 +59,23 @@ const (
OffsetTopMode = 3 // 0=Power/SWR, 1=Waveform, 2=Spectrum, 3=Setup
OffsetChannel = 4 // 0=Auto, 1..4=CH1..CH4
OffsetChannelAuto = 5 // when channel==0 (Auto), the physical channel auto is locked to (1..4)
// OffsetRange: byte 6, 0..10 = 5W..10KW, 11 = Auto. Per-channel; the
// F3 (Range) press is a no-op when byte 4 == 0 (auto-channel), same
// gating as the alarm byte at offset 7 — see VerbAvailableInState.
OffsetRange = 6
// OffsetRange: byte 6, 0..10 = 5W..10KW, 11 = Auto. Per-channel —
// each of CH1..CH4 carries its own range setting, so in auto-
// channel mode the displayed range is whichever channel auto-
// detection has currently locked to. F3 (Range) on the meter's
// front panel cycles the auto-locked channel's range; the
// displayed value may appear unstable simply because auto-
// channel keeps re-locking between presses. (An earlier
// investigation misread this as "F3 is no-op in auto-channel".)
OffsetRange = 6
// OffsetAlarm: byte 7 is an alarm-DISABLED flag (inverted polarity).
// 0x00 = alarm armed on the LCD, 0x01 = alarm off. The DataLogger
// VB6 source labelled it "Alarm State" without specifying polarity;
// confirmed inverted on 2026-05-08 by toggling F4 in CH1 manual mode
// (F4 has no effect on Ch-Auto on this firmware) while logging
// DEBUG. The decoder negates the byte before populating
// confirmed inverted on 2026-05-08 by toggling F4 in CH1 manual
// mode. The decoder negates the byte before populating
// AlarmEnabled, so the JSON/UI layer keeps a positive
// "alarm_enabled" semantic.
OffsetAlarm = 7
OffsetAlarm = 7
OffsetPeakAvg = 8 // 0=peak_hold, 1=average, 2=tune
OffsetAlarmSet = 9 // alarm setpoint index (encoding TBD)
OffsetPeakPwrHi = 23 // 16-bit BE × 0.2 W — *live* envelope peak this poll cycle
Expand Down Expand Up @@ -280,26 +284,22 @@ var KnownVerbs = map[string]bool{
// in the given state, or a reason string explaining why it will be
// silently ignored.
//
// LP-500/700 firmware quirk: F3 (Range) and F4 (Alarm) are per-channel
// settings. When the meter is in auto-channel mode (IN byte 4 == 0,
// snap.AutoChannel == true), the firmware ignores both presses — there
// is no single "current channel" to mutate. Confirmed empirically on
// 2026-05-09 by sending range_step / alarm_toggle 5× each in auto-ch
// mode and observing no change in offsets 6 / 7. The F4 case was
// already noted at decode.go OffsetAlarm; F3 has the same gating.
// Currently no verbs are gated. An earlier version of this function
// NACKed range_step / alarm_toggle in auto-channel mode based on a
// probe that observed "range doesn't change after 6 presses" — but
// that observation was actually the auto-channel detector re-locking
// to a different channel between presses (each channel has its own
// range, so the displayed range is whichever channel auto-locked to
// at that moment). On the meter's physical front panel, F3 in
// pwr/swr + auto-channel does cycle the auto-locked channel's range,
// and the firmware accepts the verb. Confirmed on the bench
// 2026-05-16 by VU2CPL.
//
// snap may be nil (no telemetry observed yet on this connection), in
// which case we let the verb through and let the firmware decide.
// Kept as a hook in case a future quirk requires per-state gating.
// snap may be nil (no telemetry observed yet on this connection).
func VerbAvailableInState(verb string, snap *Snapshot) string {
if snap == nil {
return ""
}
switch verb {
case "range_step", "alarm_toggle":
if snap.AutoChannel {
return verb + " is ignored by firmware while in auto-channel mode; channel_step to a manual channel (CH1–4) first"
}
}
_ = snap
_ = verb
return ""
}

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49 changes: 20 additions & 29 deletions internal/lpmeter/decode_test.go
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Expand Up @@ -248,36 +248,27 @@ func TestPollReportShape(t *testing.T) {
}

func TestVerbAvailableInState(t *testing.T) {
tests := []struct {
name string
verb string
snap *Snapshot
wantBlock bool
// All verbs are currently always allowed; the function is kept as
// a future hook in case a real firmware quirk surfaces. (An earlier
// version gated range_step / alarm_toggle in auto-channel based on
// a misread probe; corrected on 2026-05-16 — see decode.go doc.)
cases := []struct {
verb string
snap *Snapshot
}{
{"nil snap lets anything through", "range_step", nil, false},
{"range_step OK in manual channel", "range_step",
&Snapshot{AutoChannel: false, Channel: 2}, false},
{"range_step blocked in auto-channel", "range_step",
&Snapshot{AutoChannel: true, Channel: 1}, true},
{"alarm_toggle blocked in auto-channel", "alarm_toggle",
&Snapshot{AutoChannel: true, Channel: 1}, true},
{"alarm_toggle OK in manual channel", "alarm_toggle",
&Snapshot{AutoChannel: false, Channel: 3}, false},
{"channel_step always allowed", "channel_step",
&Snapshot{AutoChannel: true, Channel: 1}, false},
{"mode_step always allowed", "mode_step",
&Snapshot{AutoChannel: true, Channel: 1}, false},
{"peak_toggle always allowed (works in auto-ch)", "peak_toggle",
&Snapshot{AutoChannel: true, Channel: 1}, false},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got := VerbAvailableInState(tt.verb, tt.snap)
if tt.wantBlock && got == "" {
t.Errorf("expected block reason, got empty")
}
if !tt.wantBlock && got != "" {
t.Errorf("expected no block, got %q", got)
{"range_step", nil},
{"range_step", &Snapshot{AutoChannel: true, Channel: 1}},
{"range_step", &Snapshot{AutoChannel: false, Channel: 2}},
{"alarm_toggle", &Snapshot{AutoChannel: true, Channel: 1}},
{"alarm_toggle", &Snapshot{AutoChannel: false, Channel: 3}},
{"channel_step", &Snapshot{AutoChannel: true, Channel: 1}},
{"mode_step", &Snapshot{AutoChannel: true, Channel: 1}},
{"peak_toggle", &Snapshot{AutoChannel: true, Channel: 1}},
}
for _, tt := range cases {
t.Run(tt.verb, func(t *testing.T) {
if got := VerbAvailableInState(tt.verb, tt.snap); got != "" {
t.Errorf("VerbAvailableInState(%q, %+v) = %q, want \"\"", tt.verb, tt.snap, got)
}
})
}
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