* EPIRB RX: add receiver-overload indicator on channel bar
Tint the channel-power bar red when the front-end overloads (ADC near
full scale). EPIRB demodulation relies on the constant-envelope carrier
and the +/-1.1 rad biphase phase jumps; ADC clipping distorts both, so a
visible cue to reduce RF-amp/LNA/VGA gain is useful.
Implemented in the shared ui::Channel widget via an opt-in
set_overload_threshold(): when the last ChannelStatistics max_db reaches
the threshold the bar is drawn red instead of blue. Default threshold is
above the 0 dBFS ceiling, so all existing users are unaffected. The
EPIRB view enables it at -3 dBFS.
Done in the widget (main firmware) rather than the EPIRB app because the
epirb_rx external app is already at the 32 KB flash limit; the app only
pays for a single setter call.
* EPIRB RX: widen AFC capture range to +/-5 kHz
The AFC estimate was only applied after carrier lock, so carrier
acquisition ran on raw phase deltas and could only tolerate offsets of
a few hundred Hz before the 0.6/0.7/1.6 rad detection thresholds (on
the 12-sample accumulator) broke down.
Track the carrier offset continuously in the IDLE state with a
first-order loop (AFC_TRACK_ALPHA), so the de-biased accumulator
self-centers for any offset within the discriminator Nyquist (~24 kHz)
*before* the thresholds run. ALPHA = 0.005 pulls a +/-5 kHz offset
under the 0.6 rad lock threshold in ~11 ms, well inside the 160 ms
preamble / 80 ms stability window. The IDLE rise-detect threshold is
also made symmetric (fabsf) now that the bias is removed.
Also add the missing <cstdint> include to test_convert.cpp so the
application_test suite compiles under the current toolchain.
Verified: baseband_epirb_rx.elf builds (flash 53%, RAM 12%) and
baseband_test passes.
Arne Luehrs
jLynx
furrtek