[beagleboard] McBSP2 signal access?

Is there any way to get hold on the McBSP2 signals on the beagleboard.
They now go from ball to ball on the board as I2S tracks.
I would like to use an external stereo audio DAC such as TI PCM1792A.
Why is the audio sample rate on OMAP3530 limited to 48 kHz.
I would need 192 kHz. Any idea about how to get it?

McBSP2 is not accessible from the Beagle for external use. You can use McBSP3 which is accessible from the expansion connector. You can find this information in the System Reference Manual.

http://beagleboard.org/static/BBSRM_latest.pdf

The only way I know to explain why the McBSP is limited to 48MHz is because that is as fast as it runs.

Gerald

2009/11/14 Seppo Nikkilä <seppo.nikkila@innovativeideas.fi>

Thanks for your advice Gerald,

OK, I try to manage with McBSP3 even if it much less sophisticated than McBSP2…

Do you think that in the future revisions of Beagle it would be possible to connect McBSP2 signals to the TPS65950 with 33R resistors and have pins for a 4-wire flat cable on the OMAP3530 side of the resistors? This would give an easy access to McBSP2 which is the only port having the 5 KB buffer for audio. There already is a 33R resistor on the MCBSP_CLKS, would it be possible to have a pin (or plated-through pad) for it on the OMAP3530 side as well.

Yes, the McBPS design is limited to 48 MHz but this should be plenty for my 192 kSample/s stereo audio stream. The bit rate is 192,000 x 2 x (24 + 8) = 12.288 MHz, only about one quarter of the McBSP maximum. Yet TI SPRUF98D (October 2009) tells in 20.2.4.3.1 on page 2988 that the “(Supported frequencies are 8, 11.025, 12, 16, 22.05, 24, 32, 44.1 and 48 KHz).” The standard sampling rates of 96, and 192 kHz are not mentioned. Is this just because of the TPS65950?

I don’t need video in my application so can I use the DPLL3 and DPLL4 freely to generate 49.152, 12.288 and .192 MHz clocks for my PCM1792A which will be the master device?

Thank you in advance for your valuable help!

There are no plans to make the McBSP2 externally accessible on future revisions of the board.

Gerald

2009/11/15 Seppo Nikkilä <seppo.nikkila@innovativeideas.fi>