Am Donnerstag, 14. Oktober 2010, 17:28:19 schrieb Alex Lee: > On Thu, 2010-10-14 at 13:58 +0200, Julian Scheel wrote: > > One more question on the feedback: In your project you fo 10.14 for Full > > Speed devices (which mine is - the AT91SAM7A3 can't do High Speed) and > > 12.13 for highspeed. Why do you distinguish that way? Is your device > > initialised in High Speed mode whenever it's connected to a Linux host? > > I started off with the assumption that with UAC1 in FS, the specs says > 10.14. However, I'm running the widget in HS (but still UAC1), so > according to USB2.0 spec, the ISO feedback should be in 16.16 format. > Later I found out that Linux uses 12.13 (for whatever reasons), so I > changed the HS format to 12.13, leaving the FS format at 10.14. Ah ok, I see... Linux uses 12.13 in any case though? (Without the new patch of course) > My project uses the AT32UC3A3, which can operate it both HS and FS. So > it can enumerate to be either a HS or a FS device depending on the PC/ > USB Hub's capabilities. So the firmware has to cater to both cases. We > are also doing compatibility testing with Vista and Win7 (WinXP does not > support rate feedback). So we need to test HS and FS as well. OSX can > accept either 10.14 or 16.16 format, depending on whether the firmware > sends it 3 bytes or 4 bytes in the feedback pipe, so it will work with > FS or HS. Ok, being compatible with al OSes seems to be a non-trivial task... > We are also developing a version of the firmware for UAC2. So we will > have to figure out what format to use for UAC2 as well - most likely > 16.16. However, for Linux, we will need to wait for Clemens' patch to > reach the distributions. btw, there are other bugs in the alsa UAC2 > driver that Daniel has fixed, but the patches are not in the 2.6.35 > kernel - probably in 2.6.36 or 2.6.37. So currently we have workarounds > in the widget firmware for UAC2. Good to know. So far I only do UAC1, but for 192kHz I will have to switch to UAC2... May I come back to you with some questions about UAC2 then? > There are other incompatibilities as well. For example, my current UAC1 > firmware has workable mute controls when running in Windows. But in > Linux, alsamixer cannot interpret the mute/volume controls. The UAC2 > controls are interpreted correctly by alsamixer, though. Odd... I only have one control so far, a PCM mute control... That one seems to work well in Linux. > I looked at your scope traces. DATA seems to be valid at the falling > edges of SCLK. According to i2S specs, they are supposed to be valid at > the rising edges. The relationship between LRCK and DATA looks OK (ie > one SCLK delay from the LRCK edge), though. Ok, fixed both issues. Uploaded a new capture: http://jusst.de/files/i2s_plot2.png This seems to be ok for what I can say... Do you agree? > Do you get any analog output at all from the DAC? Any noise at all? Actually the module has a constant DC voltage of between 1.2 V on R+, 1.4 V on L+ outputs and between 2.2 V on R- and 2.6V on L- output.... Which actually is really odd as the I/V stage has DC block capacitors in it... This is the schematic of the DAC module: http://www.twistedpearaudio.com/docs/digital/cod_schematic.pdf Regards, Julian _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
