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TAS5756M: some questions about Hybridflow coefficients

Prodigy 190 points

Replies: 12

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Part Number: TAS5756M


I'm working on a Linux driver for TAS5756M device. And not everything is clear about it and I'm looking for some explanations especially around PBE configuration. The idea is to be able to configure all settings available from PPC2. I read TAS5756/TAS5754 datasheets + hybridflow document and I made a lot of tests from PPC2 to get some values and registers addresses for each settings.

But some area still no clear for me. Due to the lack of complete registers map for hybridflow.

So, for PBE configuration, I can see that when I set HPF value, it changes 25 coefficients at once. All of them look like biquads settings. At least one is expected to configure the high pass filter related to this feature.

But, "effect intensity" changes also the 5th to 10th coefficients from previous 25 coefficients list. So HPF and Effect intensity are changing (partially) same registers. It is strange.

Then I reversed coef of those 5 biquads to understand which kind of filters are set by this property. The result seems incorrect. 5 EQ filters around 1000 Hz, it is very high for a "high pass filter" around 50-300 Hz (value for HPF on PPC2). So I don't understand the meaning of those registers or of those filters. I'm not able to recompute myself these settings which is annoying. Maybe I misunderstood the purpose of these registers.

Can you provide to me some highlights to be able to finish this driver? Do you have somewhere a complete registers map for this device? It can simplify a lot...

I don't have also (for DBE block) the complete logic behind upper and lower mixing threshold. Apparently change high or low values are affecting two coefficients at the same time for both. So if you have some explanations about the logic there, I'm interested in.

To finish, I have two TAS5756M in stereo 2.1 setup. One is executing HF4 for mono application in low frequencies (for bass) and another one is executing HF6  for stereo in high / middle frequencies. Stereo device is routed in BTL mode and the mono device in PBTL mode. Do we have to do in software specifically to support correctly BTL / PBTL modes? Because, if I apply HF3 for both devices, the sound is by default in a (very) higher level than using HF4/HF6 setup. Of course, registers 0x3D and 0x3E are identical in both cases. I have to increase the gain to 24 dB to get same volume output than HF3 with 0 dB gain. So Maybe I missed something in the config to have the expected behavior.

Thank you in advance.