Any Crystal Semiconductor CS4231-based devices supported by this driver are programmed in AD1848-compatibility mode. This driver does not include support for advanced CS4231 features; in particular, simultaneous play/record.
Some devices can detect that the IRQ is "in use" by another device in the system. If this occurs, the driver prints an error message like the following, and you must change the IRQ setting of either the audio device or the conflicting device.
sbpro: MWSS_AD184x IRQ 7 is 'in use.'
Some devices are not able to detect such a conflict. The driver will try to use the card, but that will likely result in the system hanging when the card is first used. Thus, it is important to check that the IRQ that does not conflict with another device.
Although the sbpro driver supports A-law encoding on AD1848 and compatible devices, audiotool does not and produces an error message if you select A-law encoding. Use audioplay(1) to play A-law encoded audio files, or use audioconvert(1) to convert the A-law sample into a format that audiotool will accept, such as 16-bit linear. User-written applications can select A-law format using the sbpro driver on AD1848 and compatible devices.
Some system units have the headphone jack wired with its Left and Right channels reversed, so you hear Left output in your right ear and vice versa. The line-out jack at the back of the unit works as expected.
The quality of sound is better when using an external microphone and speakers, not the ones built into the keyboard.