Is it possible to interface a ADSP-218x Serial Port to an I2S device like a DAC?
Yes. The ADSP-218x Serial Ports are standard serial ports and do not support I2S mode. In I2S mode, there is a pin called LR Clock that tells whether the word being transmitted currently is a Left Channel Data or Right Channel Data. The ADSP-218x Serial Ports do not support such a mode. One alternative is to use the 218x Serial Port in standard mode, but use a flag pin to generate LR clock under software control. This means that the software will toggle the flag depending on which channel is being transmitted. However such an approach requires the user to take care of any timing issues as the frequency of the Serial Port increases. In this approach, the user cannot use autobuffering to send data out of the SPORT, but have to use the core driven mode.
