the tone detection currently only tracks data, not
the separator. track both instead, for improved
detection reliability.
e.g.
separator tone ≈ 9
data low tone ≈ 18
data high tone ≈ 24
two fir windows produce e.g.
freq data 9 sep 0
then 18, 9
then 24, 9
18, 9
so we take min(data, separator)
that gives 9,9,9,9
now we have the separator cluster
however, if both windows are active during transitions,
you can also capture the higher clusters, which would
allow freq_max to grow
so when you learn e.g.:
freq min = 9
freq max 24
then the learned threshold would be:
(9 + 24) / 2 = 16
and now you know how to separate the tones
fir already suppresses noise so the pulse should
be reliable. so freq/sep only go non-zero when an
actual tone exists
this should now result in being able to sync with
spkmodem encoders with no prior knowledge of the
correct tone frequences. we just use maths.
Signed-off-by: Leah Rowe <leah@libreboot.org>
since we have auto-detection now, we only need to know
that two signals exist, not that they are valid, since
the auto-detection now handles validation and fallback.
Signed-off-by: Leah Rowe <leah@libreboot.org>
a continuation of the previous patch. this waits for
currently one second, before defaulting to the hardcoded
value. otherwise, it tries to use whatever timing it
gets automatically.
this way, the program should now reconfigure its own
timing, without intervention by the user, if the timing
differs from sensible defaults.
this is because spkmodem is implementation-defined;
it's just however coreboot and/or GRUB happen to set
it up, and on the hardware in question.
Signed-off-by: Leah Rowe <leah@libreboot.org>
current logic is hardcoded, as in the original spkmodem-recv.
with this change, small differences are observed and averaged,
then the detection thresholds are adjusted accordingly.
the existing macros serve as a baseline, but real signals
differ. with this change, we therefore account for possible
drift in timings, which can change in real-time; the old
code could possibly get out of sync beccause of that, which
may have resulted in corrupt characters on the screen. this
change therefore should make the output a bit more stable.
the detection window is continually adjusted, so that the
output timings don't drift.
the tolerances are automatically adjusted based on base
timings (see new define in patch)
Signed-off-by: Leah Rowe <leah@libreboot.org>
instead of when it goes above, do it precisely on the
timeout. otherwise, if by sheer chance the signal
pauses and we reset the byte - sure, ok, but it's a
bit tight and we run the risk of advancing another
frame, depending on the timing.
this is a minor edge case, probably rarely ever
triggered in practise.
Signed-off-by: Leah Rowe <leah@libreboot.org>
Leah Rowe