Gentle(wo)men,
in the quickStartOMAPL1x_rCSL package the McASPEcho_dspL138 project is included.
Unfortunately because of a bug the project is only restrictedly useful.
Looking into the dspmm.c module you find the audio loop-back in the processing of TX Non-Error Interrupt:
mcaspRegs->XBUF11 = (Uint32) mcaspRegs->RBUF12;
It’s working fine, as long as you don’t try to change the amplitude of the output signal, e.g.
temp = (Uint32) mcaspRegs->RBUF12;
mcaspRegs->XBUF11 = (temp>>1);
you get a full crap.
I guess the bug is the same what I have once found in the Low-Level Audio Application package, namely a McASP data format off-by-one-bit error:
http://software-dl.ti.com/dsps/dsps_public_sw/c6000/web/c6747_audio_edma_app/latest/index_FDS.html,
After my bug report the issue was immediately corrected, and I hope the quickStartOMAPL1x_rCSL developmentteam will do the same.
Kindly
GenPol