Hi Rob, My board uses the Cirrus CS4340 DAC. I guess what I'd like to know is would I need to come up with a driver which will take the data from a system file (such as /dev/dsp) and feed it to the DAC or is there some sort of generic implementation out there which I can tweak? Is OSS such a generic implementation?

Thanks, Umar

On Monday, July 1, 2002, at 03:46 PM, Umar Qureshey wrote:

I am working on a custom EP7212-based board running on Linux 2.4.18. I would like to know what the "big picture" is of running mp3s on my ARM-based board. From what I have gathered, I'd need to output mad's raw PCS streams to a device in the /dev directory which would be linked to the DAC. Is this correct? How would I create this link?

Getting application PCM samples to your DAC is the business of the operating system's audio driver; the details depend on which driver you plan to use. If you use OSS, the interface is usually through /dev/dsp or /dev/sound/dsp. Actually the name is unimportant; what matters are the device major/minor numbers. Under Linux, /dev/dsp should be a character device with major number 14 and minor number 3; it can be created with `mknod' if it doesn't already exist. The device numbers link the node to the audio driver in the kernel, which then passes your PCM samples to your sound hardware.

Also, is there any special hardware initialization that needs to be done to preset the board for decoding? If someone can outline the general sequence before I delve into the details, that'll be very useful. Thank you!

I'm not familiar with the EP7212 in particular, so I'm not sure I can answer this question. However, if the board is running Linux, I imagine most of the details are handled for you by the OS.

-- Rob Leslie rob@mars.org