I'm looking for a simple solution to convert microphone audio to S/PDIF stream.
Does TI have products in its portfolio to achieve this functionality?
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For the simplest solution, the PCM2903CDB is likely your option. However, another solution is amplifying the microphone signal with a LMV1012, and then sending into a PCM9211 to obtain S/PDIF out. The total of buying both LMV1012 and PCM9211 will be around $3 if you buy both in low amount.
Hope this helped!
In my original post, I wasn't specific enough in describing the requirements: I need S/PDIF both ways (input and output).
Therefore, the PCM9211, being quite powerful, does not correspond perfectly to my application. It has S/PDIF input only (12 inputs!), but not output.
MPO0 - pin 15
MPO1 - pin 16
"The S/PDIF-encoded signal generated by the DIT module is available through the MPO0 and MPO1 pins. The MPO selection registers (Register 78h/MPOxSEL[3:0]) can be set to '1101' to determine the DIT output through one of these two pins."
After going through the IC diagram, am I correct in considering that the transmit-path (between mic and S/PDIF output) is the red line and the receive-path (between S/PDIF and speaker) is the blue line. The DOUT output (from the blue path) will go to a DAC?
May I know what exactly you want your final signal chain to be? For example: MIC -> AMP -> SPEAKER
The red line you drew is correct, but the blue line path takes in S/PDIF and output serial data, which cannot drive a speaker unless you use a DAC.
For the red line, I mentioned that the DOUT is supposed to power the DAC.
The signal chain (simplified) is duplex:
(1) MIC (digital or analog) ->MIC AFE ->S/PDIF Tx-> line driver -------- channel ---------> (2) S/PDIF Rx ->DAC ->AMP->Speaker
(1) Speaker <-AMP<-DAC<-S/PDIF Rx <----------- channel --------------- (2) line driver <- S/PDIF Tx <- MIC AFE <- MIC (digital or analog)
(1) : device 1
(2) : device 2
Thanks. Both blue and red paths you drew make sense. For the blue path, you will still need a DAC to convert the serial data to an analog signal that will drive a speaker at the end ( DOUT -> DAC -> AMP -> SPEAKER ).
The TAS2505 is an example of a digital amplifier you could use.
Hope this helped!
Before taking a solution, I would like to clarify one more point: whether S/PDIF is better than PCM for audio transmission. I'm no audio expert, but from what I've seen, S/PDIF is sort of a superset of PCM, isn't it? If the both are the same in terms of transmission fidelity, perhaps the PCM solution will be simple (or cheaper) to make.
Most TI chips support I2S and SPI encoding, which are PCM solutions. I think using I2S is the simpler and cheaper solution.
The TLV320AIC1x is a low-cost mono voice codec with a MICIN, so you don't have to amplify the signal before the DAC like in the previous solution.
Unfortunately I2S doesn't match my application, because I2S is bus: Continuous Serial Clock (SCK), Word Select (WS), Serial Data (SD). Does exist IC that feature PCM at output, not I2S ? Otherwise S/PDIF appears to be ONLY standard for audio transmitting featuring SINGLE line.