How to hold the I2S bus active when stopped

Frost_dk

Hi all.
I´m fiddling with my DAC (not a HAT), and im having a bit of trouble getting it to work as the dac will give a small tick in the speakers every 1/2 second because there is no active I2S signal. Does anyone know if it is possible to hold the I2S active when the music is stopped? If so, how?

Thanks in advance

Rune Frost
Denmark

TommyBoy

hej rune frost
kik her, måske det er samme problem ? hvilken type DAC BOARD har du ?

#3534

Frost_dk

Hi Tommy.
Thanks for the link, But it is not the same problem

. I dont have any unwanted noise or pops when the music plays. it is ONLY when the music is not playing. I believe that it is because the dac is "searching" for a i2s signal, but the Rpi stops the I2S bus, when not playing.
My question is, if it is possible to hold the I2S bus active even if the music is stopped?

Kind regards,
Rune

TommyBoy

I dont think my I2S signals ever stop, it is a DMA process thing, so it should run constantly once configured,
but I will be happy to double check tonight, (RPI3 and 0.4 beta)
your dac should not click with I2C start stop, so that is why I ask about what DAC board,
maybe its design is bad, like the link I posted, so maybe same fix, will also help for your problem.

Frost_dk

Hi again Tommy.
Thanks for your reply.
Hmm.. the dac makes the same "click" when there is no I2S signal present (when the connector is not connected at all), thats why i thought it stops the I2S flow.. My setup is a bit unusual, as my dac i really an old cd player where i have disconnected "løbeværket", and uses I2S from the rpi3

Kind regards,
Rune

TommyBoy

ha ha really smart, I got the same ida, since many of the good old DAC chips in CD players uses I2S format,
ok about the click. the older DAC types are designed to run with I2S constantly,
when it start or stop you get a click,
that is why all CD players with the older type DAC, got a mute transistor,
if you look after the opamps, you find this mute circuit,
connect a wire from GPIO RPI3 to handle the mute, and you kill the clicks.

all the new hi res DAC chips got auto detect and mute internally, so they handle this for you.
the best solution is offcourse to ask the software designers behind runeaudio to constantly clock I2S.

TommyBoy

A question : the DAC in a CD, uses only 16 bit format, right ?
rune output 16-24-32 bits, then what happens ?

what is the DAC chip called in the CD player board, you are using ?
some of them got AutoMute feature, simply enable it, it could be be default turned off,
one example CS4390 see pin 11 it should be low for automute active

TommyBoy

just double checked.. YES my rune 0.4 on RPI3 also turn off I2S when not playing..
so the mute system must work,
FEATURE SUGGEST : a GPIO pin go HI or LOW when not playing, so a muting system can be made on own hardware platforms.

hondagx35

Hi,

all arm based devices i know are stopping the I2S clocks when you stop playing a track and start it again when you start playing.

Frank

Frost_dk

Hi Frank.
Thank you for your reply.
Im sorry to hear that it is normal that it closes, but i was kind of expecting this

...
Thank you for your time

Kind regards,
Rune

TommyBoy

yo rune, what DAC chip in your CD audio project ??
check it out, and see it is normally possible to find schematics of the whole audio circuit,
look for the mute stuff