AnsweredAssumed Answered

ADV7842 I2S silent

Question asked by JustinH on Mar 19, 2013
Latest reply on May 28, 2013 by GuenterL

Hello Analog friends,

 

I am using an adv7842 in a design, and have verified, using an HDMI test source, that I am able to successfully receive HDMI audio (48 kHz, 2-channel, uncompressed) and successfully route it out I2S to an adau1701.

 

Now I am trying to use an HDMI camera, and despite reading several promising values from the chip, it doesn't seem to be producing any audio output to the adau1701. Here are some interesting registers (imho):

 

HDMI 0x04: 0x23 (TMDS PLL and audio DPLL locked)

HDMI 0x18: 0x71 (L_PCM or IEC 61937 compressed audio sample packet received)

IO 0x65: 0x8e (Layout-1 aka 2-channel, audio not muted, CS data valid)

HDMI 0x07: 0xa7 (Stereo audio)

HDMI 0x5b-0x5f: 0x22 0x55 0x10 0x16 0xc0 (CTS=140624, N=5824)

HDMI 0x51-0x52: 0x4a 0x2c (TMDS freq = 148.34375 MHz)

HDMI 0x36: 0x04 (linear PCM samples)

HDMI 0x39: 0x02 (48 kHz)

HDMI 0x3a: 0x02 (16-bit samples)

IO 0x88: 0x00 (no checksum errors occurred)

IO 0x60: 0x07 (receiving audio infoframes)

 

I do have EDID data loaded into the internal RAM that reports that the chip supports 32 kHz, 44.1 kHz, and 48 kHz audio rates. I also observed the same behavior (no audio) with no EDID data loaded into the chip, so I suspect this is not EDID-related.

 

I have also tried setting all the mute flags to zero (no behavior change, as it is not muted). I have also tried changing DIS_I2S_ZERO_COMPR (per http://ez.analog.com/message/53594), but this also has no effect (since it's not compressed audio, seemingly).

 

I am really at a loss as to what to check next. Can you help me think about what I might be missing?

Outcomes