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Author Topic: Lazarus oscilloscope - FPC firmware + Lazarus GUI  (Read 5944 times)


ccrause

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Re: Lazarus oscilloscope - FPC firmware + Lazarus GUI
« Reply #16 on: March 25, 2023, 06:09:37 pm »
A new version of the LazScope project has been released.  A few bug fixes and an 8 bit mode was added.

Attached an example trace of a middle C note played on a laptop and captured over the headphone jack.

Thaddy

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Re: Lazarus oscilloscope - FPC firmware + Lazarus GUI
« Reply #17 on: March 25, 2023, 06:19:53 pm »
Nyquist?
https://en.wikipedia.org/wiki/Nyquist_frequency

The graph overshoots so the sampling is not correct. Not good for your ears. Just like my Marshall 130 watt clone is not good to my ears: London City, just from 1966 1969, made in Amsterdam. The latter is less painful than sampling overshoots and more mellow, but too loud.

Anything recorded like that can be thrown away.

What it shows is ear problems and a bad mixer (human, not table)
And even if it is called "concert pitch" it is waaaaay to high. (My Piano tuned at 402, which is low, but more natural)
« Last Edit: March 25, 2023, 06:44:20 pm by Thaddy »
I actually get compliments for being rude... (well, Dutch, but that is the same)

Fred vS

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Re: Lazarus oscilloscope - FPC firmware + Lazarus GUI
« Reply #18 on: March 25, 2023, 07:42:47 pm »
A new version of the LazScope project has been released.  A few bug fixes and an 8 bit mode was added.

Attached an example trace of a middle C note played on a laptop and captured over the headphone jack.

Hello Ccrase.

Out-of-the-box, brilliant, nice and fast.

Big wow + congrats.

Fre;D
I use Lazarus 2.2.0 32/64 and FPC 3.2.2 32/64 on Debian 11 64 bit, Windows 10, Windows 7 32/64, Windows XP 32,  FreeBSD 64.
Widgetset: fpGUI, MSEgui, Win32, GTK2, Qt.

https://github.com/fredvs
https://gitlab.com/fredvs
https://codeberg.org/fredvs

ccrause

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Re: Lazarus oscilloscope - FPC firmware + Lazarus GUI
« Reply #19 on: March 25, 2023, 07:57:05 pm »
Nyquist?
https://en.wikipedia.org/wiki/Nyquist_frequency
The sample frequency is about 63 kHz, so should be fine for capturing a 261 Hz sine wave.

Quote
The graph overshoots so the sampling is not correct. Not good for your ears. Just like my Marshall 130 watt clone is not good to my ears: London City, just from 1966 1969, made in Amsterdam. The latter is less painful than sampling overshoots and more mellow, but too loud.

Anything recorded like that can be thrown away.
This is a "pure" sine wave sample file, played via my laptop sound chip and sampled with a simple wire via blocking capacitor and DC offset resistor divider connected to a headphone jack.  Most of the noise in the plot is probably due to either low quality onboard amplifier or ambient electromagnetic interference picked up by the unshielded probe wire.  Note that even a Rigol DS1102E oscilloscope with a proper shielded probe shows significant noise for this, so the problem is probably somewhere between the sound chip and the location of the probe.

 

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