Re: sox?


Stuart Longland VK4MSL
 

On 26/11/16 11:46, ab9ca@... wrote:
I see the TX LED light for the DB15 connector. I see an approx square
wave (maybe with some pulse width modulation) on pin 12 of the 40 pin
header. Also see signals on pins 40 and 35. But I see nothing on the
output side of the AIC3204. Looks like the needed info is going in but
the AIC3240 is dead and nothing is coming out. There is 3.3v on pin 6 of
the AIC3204. Am I reading all this correctly?
If it's completely dead, you'd not be able to set mixer controls as the
'AIC3204 would not be responding to the I²C commands. If you can set
the mixer without errors, then *something* is alive. It could be just
bad mixer settings.

On the 40 pin header, you should see one pin toggling at the same rate
as your audio sample rate, that'll be the word clock, then a second one
will be 16 or 32 times this frequency, that'll be the bit clock. The
actual audio data is on two separate lines synchronised to these, one
for transmit, the other for receive.

Format is PCM, sent most significant bit first I believe.

As for the mixer, this CODEC chip is a complex beast, and it took me
quite a while to figure out the mixer in them the first time I
encountered one. The set-up script though provides a very good starting
point, as does TI's documentation.

http://www.ti.com/general/docs/datasheetdiagram.tsp?genericPartNumber=TLV320AIC3204&diagramId=SLOS602C

That functional diagram might help explain what all those knobs and
dials in `alsamixer` do. The inputs to the UDRC from the radio are
IN_1L and IN1_R… and the output is on the line output (LO) amplifier.
The headphone amplifier is not used.

There's some resistors you can select for the input from IN* to the left
and right ADCs as well as common-mode resistors to ground, which help
set the gain. You get the choice of 10k, 20k, 40k or off if I recall
correctly. I think the set-up script for the UDRC sets those to 10k and
CM to 10k, giving a 0dB gain.
--
Stuart Longland (aka Redhatter, VK4MSL)

I haven't lost my mind...
...it's backed up on a tape somewhere.

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