Finally, there are news!
As you may remember, some 3.15 kernel (
https://git.goldelico.com/?p=letux-kernel.git;a=shortlog;h=refs/heads/omap-audio-3.15) is working on the PandaES (omap4) and there is headset audio if it is sent to the "Media LP" channel or to the "twl6040-legacy" channel. The legacy channel circumvents the AESS DSP completely (works also without firmware) while the first makes use of it.
With modern kernels where I have adapted firmware loading and fixed several bugs, I never could make the headset audio work with "Media LP"on the PandaES. Why PandaES and not the Pyra? Because I can leave it permanently connected to LAN and power and it has a headset jack like the Pyra and a single handsfree speaker can be connected. So I gave up for quite a while (everyone has more promising projects than this one).
In the meantime I tried to analyse the AE DSP (which is not a TMS320 or any other well known architecture) and could at least verify that it is doing something.
Recently, I started over to have a look and there was a first observation. Playing to "Media LP" reports that the MP3 is sent to the hardware - but at half speed, compared to the wall-clock. So I started to work on this, found that the AE Event Generator (which defines the rate samples are processed in the DSP) is running at half speed and with some help by one of the omap kernel maintainers, we could fix this by a modification to the device tree. But still there is no sound for the "Media LP" channel. Only with the 3.15 kernel (which does not need this modification).
Comparing code and even flashing new µSD cards, rebuilding firmware etc. from scratch didn't help.
At some point I digged out the omap5 evaluation board, booted and connect a headset. And to my very very big surprise, there was sound on the headset with the "Media LP" channel. With the dusty µSD that was still installed.
It turned out that it had an letux-6.13-rc5 kernel from January 2025. Likely, I simply did not recognize that it can work or did not even test audio with it.
So I flashed two new µSDs card with a rebuilt kernel, Debian 11.11 user-space. And installed the two U-Boot versions for PandaES and for the omap5 evaluation board. And I rebuilt the firmware on both boards. After connecting a headset to the headset jack, both boards play audio on the legacy channel. But the PandaES still plays silence on the "Media LP" channel while the omap5 eval board plays something!
After doing more and more checks, it is now obvious that the AESS basically works on omap5, including the Pyra. It is just the omap4 kernel variant broken which I had been using for testing...
But work even for the omap5 is still not finished to merge the code anywhere:
1) firmware build can not be done for kernels letux-6.16 or later on Debian 11.11 (some gcc version issue)
2) if the "Media LP" channel is used at least once, the "twl6040-legacy" channel gets broken (using "Legacy" once or several times before "Media LP" is no problem)
3) none of the other channels works
4) uninstalling the aess driver as kernel module may hickup the kernel
5) proper power management for the DSP is not working and disabled
6) I have not yet managed to set up the alsamixer to get sound on the handsfree speakers of the Pyra
7) there are no power-consumption tests
8) no tests if re-encoding mp3 e.g. with different sample rate works
I'll try to tidy up this a little bit over the next weeks and do more tests and then it may become possible for others to help with work to fix the final bugs.