[sdiy] Mismatch in word length with I2S (16/24 bits), it won't work ?

[Jay Schwichtenberg]

Steve,

No they are different.

I2S is a 'bus' designed to pass converter data around. It consists of a word
clock, bit or data clock and data. There is usually a 256x, 384X or 512X
master clock used to provide internal clocking to the converter too. I don't
know if that is part of the I2S spec. You might want to grab something like
the Crystal CS4390 or some other data sheet and take a look at it. What most
people don't know is there is a spec (connector & drivers/receivers) for
running the I2S signals in parallel between seperate devices. We usually use
SPDIF or AES/EBU or light pipe because it is different.

I2C is used to pass non-syncronous data aound between chips (converters are
syncronous and the timing is verty critial). My experence is that it's
mainly used to program chips vs pass data between chips. I think that come
converters have both I2S and I2C. I2S for the converter data and I2C to
program the features of the chip. Some instrumenation converters also use
the I2C interface for data.

Jay
  -----Original Message-----
  From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Steve Allen
  Sent: Thursday, February 12, 2004 8:13 PM
  To: Jay Schwichtenberg; diy
  Subject: RE: [sdiy] Mismatch in word length with I2S (16/24 bits), it
won't work ?




  Jay Schwichtenberg <jays at aracnet.com> wrote:
    Linium,

    I'm not experienced with the BB chips. But! I have experience with some
    Crystal and AKM chips. A lot of their chips have programmable options
for
    the type of interface. Most new chips will include I2S

    Is this the same as Phillips I2C Bus....?



    MSB or LSB first or
    both. Some have other interfaces also, but I2S is the standard. There is
no
    2 starting bits either. Data is clocked with respect to the bit clock
and
    word clock with 1 bit per clock.

    I looked at the data sheet for the TDA part. It's obsoleted on Philips
WEB
    site and the data sheet is pretty mininal. If you're looking at 16 bits
    because of cost don't. 24 bit DACs aren't that expensive. I would blow
the
    16 bit parts off and look at 24 bit multi-bit parts. There are a number
of
    cheap DACs out there that are targeted for multi-media. Multi-bit ones
are
    much more tolerant of clock jitter. Biggest problem with new parts is
you
    may not find it in a DIP package.

    If you're stuck with the TDA or PCM you might try contacting the
manufacture
    and see what they say about clocking it with 24 bit data.

    Jay


    > -----Original Message-----
    > From: owner-synth-diy at dropmix.xs4all.nl
    > [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Linium
    > Sent: Thursday, February 12, 2004 9:13 AM
    > To: diy
    > Subject: [sdiy] Mismatch in word length with I2S (16/24 bits), it
won't
    > work ?
    >
    >
    > Hello,
    >
    > I was reading the specs of the DIR1703, and discovered that this
    > puppy will
    > produce I2S digital out only in 24bit word.
    >
    > I intended at first to use the DAC TDA1543 but the specs say it
    > accepts 16bits
    > I2S input.
    >
    > Well, i am not very aware of the I2S format, but really i think
    > it won't work.
    > The I2S word is composed of 2 start bits for nothing, then the
    > signal is a LSB
    > then a MSB.
    >
    > I am afraid that if a 24bits signal is received, the last byte will be
    > ignored, and it is the most meaningfull...
    >
    > Does some have an idea about this ?
    >
    > Well, i have a DAC PCM56U offered by! TI as a replacement, but i
    > will be happy
    > to know if I2S is notoriously available as 16 and 24 word length.
    >
    > Linium
    >





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