[alsa-devel] full duplex AD1848 (was SC-6000 driver)

Rene Herman rene.herman at gmail.com
Fri Sep 7 14:00:59 CEST 2007

On 09/07/2007 10:34 AM, Krzysztof Helt wrote:

> According to a datasheet, the AD1848K (which was a popular version of
> AD1848) is full-duplex (can work in single-dma mode or with two dma
> channels).

Yes, I see...

> The AD1848 in my SC-6000 is not the K version (at least it is not marked
> on the chip) but I saw a photo on the net with SC-6000 and AD1848K (it
> had no YMF-262 chip but a different one).
> I am looking for the AD1848 datasheet  for the pre-K version (or list of 
> differences between K and earlier versions).

Can also only find the K datasheet. Not sure what's up with that -- the 
existing ad1848 driver is simplex only.

> Also, I would like to know how you put your SG card into full-duplex
> mode.

That may be the easiest test yes. Try setting bit 2 of mss_config (| 4). 
This seems to be the generic way to enable duplex on mss/wss and it works 
here. The capture channel is fixed for a fiven playback channel:

P = 0 ==> C = 1
P = 1 ==> C = 0
P = 3 ==> C = 0

By the way -- I'm running into a bug somewhere in cs4231_lib where sometimes 
the playback IRQ stops firing when you start a capture. Stopping both the 
capture and playback and then re-starting the playback works, after which 
things may or may not hang again at re-starting the capture.

Could also be a hardware bug I guess -- will need to test further again 
(sigh). But just in case you'd also run into this, don't give up on 
ful-duplex if it only sometimes doesn't work right, as there might very well 
be a bug lurking in cs4231_lib.

(bug cannot be in my own code, as that's just setup and nowhere to be found 
anymore when things are running).


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