Hi,
It may not answer exactly your question but if you want to get audio in and out of the TM4C123 Launchpad have a look at the 'Example Programs for TM4C123 and WM8731 using MDK-ARM' resource here* - the code implements I2S emulation on the TM4C123 and full details of the design of a simple audio Boosterpack for the TM4C123 Launchpad are provided. The Boosterpack uses a WM8731 codec - the same one used on the C6713 DSK - and is relatively easily fabricated (it can be hand-soldered). It is not the same as the ill-fated CircuitCo audio Boosterpack for the TM4C123 Launchpad.
*The details are on the companion website for the book 'Digital Signal Processing Using the ARM Cortex M4' published by Wiley.
Donald