Audio-Widget not working and MCLK => 24.576MHz?

[dspv...@gmail.com]

Hello everybody,

I am new to this group. First of all, thank you for your great work so far!

I am currently building an audio-widget clone with some other hardware around it. I made my own PCB layout. So far the AVR32 does show the DFU interface when I set it to programming mode, programming the widget binary via dfu-programmer on Ubuntu seems to work. At least no error messages. ;-)

But I have two question because I can not get it running yet:

1) Once the audio-widget is installed it does not show up in the USB devices list after rebooting the the AVR32 but I can still set it back to programming mode.

Now I recognized that I forgot to connect the AD_MCLK on pin 13. Can it be that the USB Audio task is only started when a clock signal is detected on this pin and since I do not drive this pin yet the device does not show up in the USB list?

2) If I have to drive the AD_MCLK can it be changed to 24.576MHz? The schematic states that it is a 12.288MHz clock, but in my application I have only 24.576MHz available. Thus, it would be nice if I can directly feed this clock to AD_MCLK instead of adding a frequency divider. If it is possible, what do I have to change in the audio-widget software? Hopefully it is an easy hack...

Raphael

[Ing. Ondřej Lutera]

Hi Raphael,

1) I thik yes. My dac with widget is detected when some clock is on mclk input. I think some toggle should be enough for usb enumeration. I was same problem when I did my dac a few years ago :)

2) I guess Jaroslav did some tweaks to the firmware to support mclk 24.576 / 22.5792 . But I am not sure if it is integrated to the stable fw.

Best,

Ondrej

Dne 25. 2. 2018 21:30 napsal uživatel <dspv...@gmail.com>:

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[Børge Strand-Bergesen]

Hi, 

The presence of MCLK is essential. Without it the DMA-like output mechanisms don't start properly. The same goes for the clock cross coupling of IO pins. 

As for clock division I have re-purposed PA03 as a clock division sensor. Unmounted, internal software pull-up will make it read as '1'. That's the case with old Audio Widgets with hardware /2 clock division. In my newest hardware I use no division, and a resistor to ground is connected to PA03. The sensing pull-up is only applied briefly, and does not consume power over time. I suggest you add the same resistor to your hardware. Then the latest audio-widget-experimental code will divide by a further factor 2 inside the MCU. 

Likewise, PA04 is used to differentiate between common-anode and common-cathode LEDs. 

I haven't yet come around to publishing the new schematic, so here it is in the attachment. 

Cheers,

Børge

[dspv...@gmail.com]

Hi,

many thanks. I'll try this this weekend. Unfortunately I used PA03 for something else, but should be possible to shift it, either my function or the sensing.

Raphael

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[Børge Strand-Bergesen]

Ok. What are you making?

Best,

Børge

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[dspv...@gmail.com]

I am building a plate amp with DSP and UAC2 support.

[dspv...@gmail.com]

Good morning,

just another question: I noticed that there are several tasks started. Assuming the MCLK (12.288MHz or 24.576MHz) is not supplied yet, do the other tasks except the UAC1/2 task run or are they waiting for MCLK, too?
Reason: I would like to send some configuration via I2C before MCLK is started.

R.

[Børge Strand-Bergesen]

You’ll have to try it in the code. There is a simple task with live indication over UART which should always run. With it in place you can experiment with starting the others. 

Børge