2013/11/13 Miguel Angel Ochoa Rodriguez maochoa@tecnipyme.com
- In event of failure to implement GPIO , I noticed that the photos of
The first prototype boards last is eliminated auxiliary bus had on top
The Bus on top is a 44 pin header, 30pins are RGB/TTL, 8 are GPIO, 2 are
I2C, 2 are RX/Tx, and the last 2 are 5VDC and >GND.
Are you sure in the last EOMA68 A20 Boards have this conector?¿?
In the news Photos of working examples in april and may dont see this conector http://rhombus-tech.net/allwinner_a10/news/
In the case of A20 plate actually incorporates an auxiliary bus 44pins.
It would be possible to extend or modify the bus to enter the i2s??
Extending the spec to include i2s or s/p diff requires the SoC to provide either. Or additional hardware needs to be added to the already cramped EOMA card. Regardles of the SoC used AllWinner Axx, Freescale iMX.x,
If I'm right in the project OLINUXINO implemented several lines of cpu to the same pin expansion connectors with a choice of system function pin
https://github.com/OLIMEX/OLINUXINO
2013/11/13 luke.leighton luke.leighton@gmail.com:
Modifying the specification at this point in the EOMA68 seems unlikely,
not a chance. audio was one of the first things that was eliminated from putting out over the 68 pins due to there being no clear common audio standard. it is left to implementors to decide what ICs to place on the I/O board, USB audio being the most sensible and self-contained option.
For us this would be the second option since we have found that using converters usb light generated synchronization delays in the video / audio. that must be corrected through the player (XBMC - MPlayer).
Both PulseAudio has audio delay options for syncing multiple outputs like network linked pulse audio devices (Like Logitech SqueezeBox, Sonos, etc). I believe ALSA (drivers) also has(have) delay parameters. Obviously because expecting every sound source, eg. Mplayer, FireFox, Audacity, VLC, etc., to sync them selfs is unthinkable.
By contrast, in the tests we've done with CPU integrated SPDIF not
have these delays. (Important in case of decoding DTS or DOLBY
S/P Diff does not support DTS-HD/Dolby true HD. Max 192Mhz/24Bit is not enough bandwith. And a lot of HW only accepts i2s should be capable but only if all component support such a high bitrate. I think in i2s no min max bandwith is specified HDMI audio does support DTS-HD/Dolby true HD.
The only usefull/low cost standard available left is USB.
Most audiophiles prefer USB because, among the above, it lets you do DAC outside the digital LF and HF noise environment a computer is.
Yes A/V sync is a b*tch but nothing new. Usually the regular PCI/SoC audio drivers already contain the correct timings because the position of all components is sort of fixed. Even in windows. With USB the infrastucture tends to be a bit more differential, controllers, hubs, same audio chips used in different config and pcb layouts.
And thus requires a bit more tinkering.
Good luck!
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