Q: operation 1: mp3 play from LINE_IN to LINE_OUT
A. This configuration seems to be meaningless. Actually, LINE_IN is the analog input of ADC that digitizes an input analog audio signal and sends resulting conversion data to host through the I2S digital interface for processing. LINE_OUT is the analog output of DAC that takes a digital audio data from host through the I2S interface and converts them to analog form. Of course, the configuration where an analog signal from LINE_IN is converted to digital data that then are sent through I2S to host that loops them back to I2S then to DAC that plays an anlog signal back through LINE_OUT is possible, but seems to be meaningless. Another way to do that is to pass digital data internally from ADC to DAC through the Digital Audio Processing (DAP) block. For more information, please refer to the SGTL5000 documentation, available on the Freescale web site:
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=SGTL5000&nodeId=01435959C0&fpsp=1&tab...
Q. operation 2: voice from MIC to Headphone
A. This configuration is possible only as described above (i.e. digital data loopback through host or internally through DAP). The only available direct analog path from SGTL5000 inputs to outputs is LINE_IN to Headphone OUT.
Q. Can I use LINE_IN and MIC as the same time?
A. No. Only one analog input is available at a time.
Q. Is ALSA driver is enough?
A. Not all of the SGTL5000 functions may be available through the ALSA driver. A custom software may be required for some cases.
Regards,
