I am developing an ALSA driver for the AD1938 codec on uClinux for
Blackfin (I don't believe my problem is specific to that
platform). When I set up the snd_pcm_hardware_t structure with
.formats = SNDRV_PCM_FMTBIT_S32_LE,
I can run both "aplay < /dev/urandom" and an OSS test application
("tone") that sends a sine wave, but the sine wave is "inside out"
(see <http://www.link-comm.com/temp/inside_out.gif> for a screen
shot) because the codec needs unsigned data.
If I set up the snd_pcm_hardware_t structure with
.formats = SNDRV_PCM_FMTBIT_U32_LE,
the OSS test application sends a nice sine wave, but aplay fails with
the following messages:
root:~> aplay < /dev/urandom
ALSA sound/blackfin/ad1836.c:1050: snd_ad1836_playback_open
Playing raw data 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono
snd_pcm_hw_refine()
ACCESS = 00000000ffffffffffffffff -> 0000000000000008
FORMAT = 0000000000000400 -> 0000000000000000
snd_pcm_hw_refine()
ACCESS = 333f8fc000a32c60c0333f8fc -> 333f8fc000a00000008
ALSA lib ALSA sound/blackfin/ad1836.c:1172: snd_ad1836_hw_free
../../../src/pcm/pcm_params.c:2152:(snd_pcm_hw_refine_slave) Slave
PCM not usable
aplay: set_params:882: Broken configuration for this PCM: no
configurations available
I am working my way through the ALSA source, but I have not yet
figured out why aplay won't work with the unsigned codec
configuration. Any suggestions?
Steve
P.S. A more complete log of the console output with both settings
for those commands and most of the info from aadebug can be found at
the following URLs:
<http://www.link-comm.com/temp/SNDRV_PCM_FMTBIT_S32_LE.txt>
<http://www.link-comm.com/temp/SNDRV_PCM_FMTBIT_U32_LE.txt>
---
Steve Strobel
Link Communications, Inc.
1035 Cerise Rd
Billings, MT 59101-7378
(406) 245-5002 ext 102
(406) 245-4889 (fax)
WWW: http://www.link-comm.com
MailTo:steve.strobel@xxxxxxxxxxxxx
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