SRC Pairs on ADAU1442/5
Is there a requirement to use the SRC's in order on the ADAU1442 or 1445? When using SRC pair 0 in and out, I get data just fine. When using ASRC pair1 while pair0 is unused the data stops. Pair 1 starts working when I give ASRC pair0 an input, even if it's unused and has no data going into it.
Is this normal?
When I see the work "pair" I assume stereo, is that right? Does it have some other meaning relating to a pair (x2) of ASRC stereo channels?
Audio Signal Processors
src
adau1442
adau1445
rate
SigmaDSP Audio Processors
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Hi,
Sorry for the delay. For the past few days, I tried to duplicate this issue, but I can't seem to see what you're seeing. In my tests I did the following:
Attach two different audio inputs to two different serial ports.
Route the two different serial port inputs to two different ASRCs (the audio is routed in stereo pairs, as you mentioned... that is to say, the left and right channels from each input are routed together and cannot be seperated).
Set the ASRC output rate for each ASRC in use to DSP rate.
Probe the ASRC outputs in the core using a readback cell in SigmaStudio.
I tried the following tests and the audio always passed through, with no dropouts:
Test 1: ASRC0 gets Serial Input 0; ASRC1 gets Serial Input 1.
Test 2: ASRC0 gets no data, no rate; ASRC1 gets Serial Input 1.
Test 3: ASRC0 gets Serial Input 0; ASRC1 no data, no rate.
Test 4: ASRC0 gets Serial Input 1; ASRC1 gets Serial Input 0.
Test 5: ASRC0 gets no data, no rate; ASRC1 gets Serial Input 0; ASRC2 gets Serial Input 1.
That seemed like the full range of applicable test cases and they all worked out fine. Could you please post your project file or register settings for confirmation?
NOTE: There is a caveat when using the ADAU1445. Please see this section of the datasheet (Rev. C, page 55):
In the case of the ADAU1445, each output from the stereo ASRCs can have a separate data output; however, all outputs from Stereo ASRC[3:0] must be synchronous to each other, and all outputs from Stereo ASRC[7:4] must be synchronous to each other.
The first group of ASRCs (Stereo ASRC[3:0]) takes its output rate from the setting on the Stereo ASRC 0 output. The output rate for Stereo ASRC[3:1] is automatically set to this rate, ignoring the settings for the Stereo ASCR[3:1] outputs. The second group of ASRCs (Stereo ASRC[7:4]) takes its output rate from the setting on the Stereo ASRC 4 output. The output rate for Stereo ASRC[7:5] is automatically set to this rate, ignoring the settings for the Stereo ASRC[7:5] outputs.
So, as you can see, if you set the ASRC0 to "no rate", the ADAU1445's ASRC1, ASRC2, and ASRC3 pairs will effectively be muted.
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Thank you,
EZ Admin
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