I've looked at the wave forms in audacity, and tried to manually figure
out if it made any sense. I think at one point I got a 'S.P.K.' which
now having located and read the code that actually generates the tones.
Is consistent with it's startup sequence of trying to say 'SPEAKER'.
However spkmodem-recv still just prints illegible symbols.
On 6/12/21 11:59 pm, Peter Stuge wrote:
Keith Emery wrote:
When I enable spkmodem in the coreboot config, I get output from the PC
speaker. But spkmodem-recv interprets the tones as consistent gibberish.
The output is consistent with a mismatch in the baud rates, but there
appears no apparent way to select anything different in the
spkmodem-recv software.
spkmodem uses a fixed baudrate, IIRC 1200.
Did you look at a recording in a spectrum analyzer software? Maybe
that would help identify modulation timing issues.
Because coreboot isn't being loaded from the SPI chip one instruction at
a time. It's using the CPU cache as ram and executing from there... derp.
More sleep, more coffee. Those are basically the same thing, right!
If the CPU is running coreboot as fast as possible while receiving
those instructions from a relatively slow SPI bus. Is it possible
that I've somehow overclocked the SPI bus, leading to a mismatch in
the baud rates?
SPI isn't involved in tone timing, I think only the (emulated) legacy
timer is used for that.
//Peter
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