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Thanks for the datasheet Gordon!

Ha! I think I got it. surprise surprise... the lower significant 8 bits are always 0... so, reading the datasheet - it is indeed padding. There is a table in page 39 with the modes of the wm8731. I'll look to the alsa driver to check if the mode is being correctly set (it seems ok indeed), and check the samples match what is in the datasheet - which should.

- Rafael

On 2/5/24 08:59, Rafael Diniz wrote:

This makes things even more strange of how data is packed. I'm getting samples, for example , 236775168, which is way more than 2^24. May be the data is shifted 8 bits to MSB? I'm dividing the samples by 2^31 - 1, the end of scale of 32 bits.

- Rafael

On 2/4/24 21:07, Gordon Gibby wrote:

Those are 24 bit a to D ?converters. ?They have 80 to 90 DB dynamic ranges from the spec sheet. They are 30 or 40 or 50 DB more than we need!

Some people are selling systems with only eight bit eight bit ADC and that sounds pretty crappy but these are astonishingly good

On Feb 4, 2024, at 16:03, Dave, N1AI <n1ai@...> wrote:

?On Sun, Feb 4, 2024 at 03:48 PM, Gordon Gibby wrote:

??? Dave, to give an accurate answer will take a little bit of study,
??? but remember these things work in an environment of positive
??? supply voltages, without any negative supply voltage. So it’s
??? likely that they only measure positive voltages. There are no
??? negative voltages. And it’s also likely that the analog to
??? digital converter is CD quality, with far more bits than our
??? communications grade channel can support with a normal
??? transceiver. So wasting 3DB worth of dynamic range may be
??? negligible. I think I remember comments to that subject much
??? earlier, when I get the chance I’ll go back and look at it, busy
??? trying to make measurements to protect our new EOC from noise
??? generators… Head is spinning with numbers

Thanks, Gordon, for the insights.? They are a good start!

--
Regards,
Dave, N1AI