ADAU1452 SPDIF Input issue
Hi,
I've built a custom PCB with ADAU1452 and everything is working quite well except for the SPDIF input.
I think I've configured everything the way it should be, but no audio can be heard. My current setup is as follows:
1. Serial Port 1 (input) is used to receive data from an ADC (works just fine)
2. Serial Port 1 (output) is used to transmitt data to a DAC (work just fin)
3. SPIDF In/Out interfaces are complete copy of ADAU1452 eval board.
I've already verified that ASRC 0 by routing Serial Audio to and from it.
See attached images for configuration.
P.S I'm using Sigma studio 3.11, Build 1, Rev 1356
Audio Signal Processors
adau1452
spdif
SigmaDSP Audio Processors
Any suggestions?
Hello Shiaw,
Can you provide details on your SigmaStudio signal flow? Since you are using ASRC0 to read data from the SPDIF RX, are you reading from ASRC channels 0/1 in Sigmastudio? Looking at your "Core Control" screenshot I see a Panic Flag bit set, and ASRC0 error.
Attached are 2 SPDIF TX-RX audio loopback projects which you can run on the ADUA1452-MINIZ board to test both the SPDIF transmitter and receiver, which might help you isolate your problem on your board since you say both circuits were copied from the eval board schematics. The two projects are configured with the following audio path (48 kHz fs):
1. AD1838 ADC0 (stereo audio ch 0/1) --> DSP Core --> SPDIF TX --> SPDIF RX --> ASRC0 --> DSP Core --> AD1938 DAC0 (stereo output ch 0/1)
2. Generate tone sources on DSP Core --> SPDIF TX --> SPDIF RX --> ASRC0 --> DSP Core --> AD1938 DAC0 (stereo output ch 0/1) (48 kHz fs)
If I remove and reinsert the optical cable either on the SPDIF output or input connectors on the ADAU1452 eval board, the audio will automatically relocks on the SPDIF input just fine.
-JT
Hi JohnTo,
I've actually figured it out (kinda), so here it goes:
1. I've outputted audio on wrong s/pdif channel (from my computer), duh! Somehow both of them were called
Digital Audio (S/PDIF), however, one of them was an Internal ATAPI Jack, while the other one was actual
Optical Output.
2. When the issue above (more like a user error) was fixed, another one appeared, still no audio, but ADAU
complained about "Lock bit detection". So I armed myself with a scope and started to scope around the PLR135/T8
optical module, working my way towards the DSP. It looked like the optical module was operational and was
indeed feeding data to ADAU.
I've put my headphones on and began to scope (again) around the module, particulary around the coupling cap
between the output of the optical module and dsp input. Suddenly the audio appeared once the probe head
touched the side of cap and disappeared when probe was removed.
So a shunt element was needed between the output of the optical module and ground. This somehow contradicts
the schematic of the evaluation board which says that a pull-up of 10k is needed (for veeeery short distances it may be sufficient), optical module datasheet tells you even less.
So I de-soldered the pull-up and installed the shunt (about 100 Ohms).The audio path worked just fine.
I'm guessing that output from the optical module has some serious overshoot issues, so it's
a good idea to reserve a space for a shunt/series termination resistors if distance is large.
I can't really verify this, because my scope bw is pretty limited, but this seems like the only reasonable explanation.
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