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

[René Schmitz]

Hi Linium and List,

Well, I'm not really sure, but I *suspect* be that they intentionally
send the LSB first, to be able to use just the last 16 Bits clocked in
with a 16Bit convertor and everything with 24Bit convertor....
(Internally there is probably a shift register, if you clock in more
data than the width, only the most significant bits would stay in there,
and the least significant bits would fall into the "bit bucket" at the
other side. The actual conversion would be started with some sort of
word clock input...)

Cheers,
  René

Linium wrote:
> 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
> 
> 

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159