Encode audio in S/PDIF format

[AnalogSteph]

https://www.ti.com/lit/ds/symlink/pcm3052a.pdf

Neat! The converters aren't anything special, obviously, but everything up to the mic input is taken care of, you can even filter the mic bias voltage to your heart's content. (I would be tempted to add a bit more C than the 10 µF they suggest, depending on what you can afford.) Input noise seems quite good by electret mic standards. Use twisted-pair wiring to hook up the capsule.

The evaluation module is NLA but here is its manual:

https://www.ti.com/lit/ug/sleu079/sleu079.pdf

Control software is still downloadable as well, though no doubt ancient.

 

[Pavel_47]

Thanks.
UDA1355H seems obsolete.
PCM3052 features S/PDIF at output only. I need in both directions.
There is another interesting IC, that features S/PDIF in both directions: PCM9211.
But before comparing S/PDIF-based solutions, I wonder if S/PDIF is the only audio transmission interface that has a single line ?
Other popular interface is I2S, but it is the 3-signal bus: Serial Data (SD), Serial Clock (SCK), and Word Select (WS).

 

[sarumbear]

PCM3052 features S/PDIF at output only. I need in both directions.

You asked: “I wonder if there is a single device that accepts mic audio as input and outputs S/PDIF stream?” Besides, what will the SPDIF input be used for, you mention microphone as input but no analogue device for output.

There is another interesting IC, that features S/PDIF in both directions: PCM9211.
But before comparing S/PDIF-based solutions, I wonder if S/PDIF is the only audio transmission interface that has a single line ?
Other popular interface is I2S, but it is the 3-signal bus: Serial Data (SD), Serial Clock (SCK), and Word Select (WS).

You went from I’m looking for an IC to how should I design. SPDIF is device to device communication standard, I2S is an inter device communication method. You may want to first write down the specifications of your device then think on a design.

 

[Pavel_47]

You asked: “I wonder if there is a single device that accepts mic audio as input and outputs S/PDIF stream?” Besides, what will the SPDIF input be used for, you mention microphone as input but no analogue device for output.

I was unclear in the first post, sorry. The objectif is full duplex over some custom channel, i.e. something like this:
(1) MIC (digital or analog) ->MIC AFE (if analog) ->CODEC-> line driver -------- channel ---------> (2) line receiver->CODEC->DAC ->AMP->Speaker
(1) Speaker <- AMP <- DAC<- CODEC <- line reciever <----------- channel ------------ (2) line driver <- CODEC <- MIC AFE (if analog) <- MIC (digital or analog)
(1) device 1, (2): device 2.
As for the generic term CODEC, it can be either a device that outputs S/PDIF or a serializer/deserializer device that receives I2S as input and provides a serialized single line stream (for the serializer ) or a deserialized single line stream in a 3-signal I2S bus (for the deserializer) ... e.g. MAX9205/MAX9206.
In the case of S/PDIF, the candidats are PCM3052A, PCM2903CDB, PCM9211, LMV1012, pair (DIT4096, DIR9001), ADAU1452, D2-6 Family Audio SOC (from Renesas).
According to my research so far, the most cost-optimal solution seems to be using the pair (DIT4096, DIR9001).

 

[sarumbear]

I was unclear in the first post, sorry. The objectif is full duplex over some custom channel, i.e. something like this:
(1) MIC (digital or analog) ->MIC AFE (if analog) ->CODEC-> line driver -------- channel ---------> (2) line receiver->CODEC->DAC ->AMP->Speaker
(1) Speaker <- AMP <- DAC<- CODEC <- line reciever <----------- channel ------------ (2) line driver <- CODEC <- MIC AFE (if analog) <- MIC (digital or analog)
(1) device 1, (2): device 2.
As for the generic term CODEC, it can be either a device that outputs S/PDIF or a serializer/deserializer device that receives I2S as input and provides a serialized single line stream (for the serializer ) or a deserialized single line stream in a 3-signal I2S bus (for the deserializer) ... e.g. MAX9205/MAX9206.
In the case of S/PDIF, the candidats are PCM3052A, PCM2903CDB, PCM9211, LMV1012, pair (DIT4096, DIR9001), ADAU1452, D2-6 Family Audio SOC (from Renesas).
According to my research so far, the most cost-optimal solution seems to be using the pair (DIT4096, DIR9001).

So you are building an intercom that connects over a digital line? How far apart the devices can be?

 

[Pavel_47]

Yes. The distance is not specified. It is variable, say 2 ... 30 m.

 

[MaxwellsEq]

Do you need to use a standard like S/PDIF? There are probably many easy to to implement proprietary solutions.

 

[sarumbear]

Yes. The distance is not specified. It is variable, say 2 ... 30 m.

Then neither SPDIF nor I2S can work for you.

As I said earlier, write the specifications of the device then research every item’s specs.

 

[DonH56]

For 30 m you need AES3, not S/PDIF. But this whole thread seems to be a rambling "define as you go" sort of thing. As @sarumbear has said, it would be wise to define and present all the specs and the use cases, then look at the device(s) needed for the application. You may want to try the DIY section; this area is generally for commercial products (consumers, not designers or manufacturers).

 

[Pavel_47]

Then neither SPDIF nor I2S can work for you.
As I said earlier, write the specifications of the device then research every item’s specs.

I2S won't work, that's for sure, because I2S is a bus. To be used in my app I2S must be serialized.
But why SPDIF will not work. After all, it's a one-wire signal.

 

[voodooless]

But why SPDIF will not work. After all, it's a one-wire signal.

Because it’s rated up to 10m of cable length. As others pointed out, beyond that you’ll need AES. You may put together some LVDS type of transmission over CAT5 cable with the same protocol.

Why not go the wireless route? Two Bluetooth transceivers should do it, although 30m may be a stretch.

 

[Pavel_47]

it would be wise to define and present all the specs and the use cases, then look at the device(s) needed for the application.

Well, I assume that at the beginning I wasn't clear, but concerning to spec I presented them before:
(1) MIC (digital or analog) ->MIC AFE (if analog) ->CODEC-> line driver -------- channel ---------> (2) line receiver->CODEC->DAC ->AMP->Speaker
(1) Speaker <- AMP <- DAC<- CODEC <- line reciever <----------- channel ------------ (2) line driver <- CODEC <- MIC AFE (if analog) <- MIC (digital or analog)
(1) device 1, (2): device 2
Probably one more detail: the channel is not cable, nor twisted pair, but light.

 

[MCH]

I2S won't work, that's for sure, because I2S is a bus. To be used in my app I2S must be serialized.
But why SPDIF will not work. After all, it's a one-wire signal.

I am certainly not an expert, but the spdif transceivers i know, including some of the ones you mention, use separate pins for input and output. If you want full duplex with a single spdif wire, you will need some sort of mux or relay system to change from output to input, that works simultaneously on both ends. I don't know if that's easy to achieve or not. If the distance is 20 meters, how do you plan to do it? just honestly curious.

 

[voodooless]

Probably one more detail: the channel is not cable, nor twisted pair, but light.

Toslink also only goes upto 10m reliable (official spec is only 5m). You may go for some real glass fiber solution. That would work over longer distances. Toslink over SFP or similar. You’ll get two directions for free

 

[Pavel_47]

Toslink also only goes upto 10m reliable (official spec is only 5m).

Light does not necessarily mean optical cable.

 

[Pavel_47]

Why not go the wireless route? Two Bluetooth transceivers should do it, although 30m may be a stretch.

In this app using all wireless stuff is impossible.

 

[voodooless]

It keeps on getting more vague instead of more concrete…

Light does not necessarily mean optical cable.

So what does it mean?

 

[Pavel_47]

So what does it mean?

This means that the light is not transmitted through the cable.

 

[voodooless]

.. so clearly you left out some more details ..

 

[Pavel_47]

.. so clearly you left out some more details ..

The details of light transmission seem outside the scope of this forum.
Regarding the topic of this forum, it seems that I found a good formula: find a solution as efficient as possible (means the least components and the least expensive) which does 2 things: (1) convert mic signal to 1-wire digital stream (2) convert 1-wire digital stream to analog audio signal