TAS5805M: Volume control though Linux driver

Damien Miliche

Part Number: TAS5805M
Other Parts Discussed in Thread: TAS5825M

Hi,

I found out about the Linux driver for the TAS5805M shared in this post

However, I don't understand how it should be used; my knowledge of the audio architecture in Linux is quite limited.

Actually, I would like to use the TAS5805M as an external amplifier for an already existing, but limited sound card, having its own Linux driver.

What would be the best way to integrate it to a Linux system as volume controller?

Thanks in advance for your help.

Damien

over 4 years ago

0 Caro Walter over 4 years ago

TI__Mastermind 19782 points

Hello Damien,

Attached is the linux code for the TAS5805M, which should also be in the thread answered by Andy.

Additionally, attached is a how to implement for the TAS5825M, but it applies to the TAS5805M since they both have the same start up sequence.

TAS5825M Linux Driver and Startup Procedure.pdf 6866.Linux Driver for TAS5805M.zip

All the best,
Carolina

0 Damien Miliche over 4 years ago in reply to Caro Walter

Prodigy 50 points

Hi Carolina,

thanks for your reply, but this does not help me: I am able to compile and to load the driver, that initializes the TAS5805M through i2c.

What I don't know is how to interact with it to control the volume from my Linux system.

In other words, how can I reach the tas5805m_set_volume driver function? Does it create any sysfs interface?

How to make alsamixer know about it?

Thanks.

Kind regards,

Damien

0 Caro Walter over 4 years ago in reply to Damien Miliche

TI__Mastermind 19782 points

Hello Damien,

I am not very familiar with Linux, however do these threads answer your question:

https://e2e.ti.com/support/audio/f/6/p/808350/2991564?tisearch=e2e-sitesearch&keymatch=linux%2525252520tas5805m#2991564

https://e2e.ti.com/support/audio/f/6/t/724132?tisearch=e2e-sitesearch&keymatch=linux%252520tas5805m

In the threads, Andy suggests that PPC3 application is the easiest way for end system integration.
This can be done by:

1. Selecting desired settings in register map/tuning and processing.

2. End system integration tab -> Dump current state into a header file

Additionally, the I2C monitor at the bottom of the GUI can be used to log all I2C transactions.
For example: Changing digital volume to 0x20:

w 58 00 00
w 58 7f 00
w 58 00 00
w 58 4c 20

All the best,
Carolina

0 Damien Miliche over 4 years ago in reply to Caro Walter

Prodigy 50 points

Hi Carolina,

thank you for your answer.

Unfortunately, those threads do not help neither: I have been able to generate an initial registers configuration through PPC3, and it is properly loaded by the Linux driver through i2c.

The only missing part is how to manage the volume control at runtime using that driver.

Kind regards,

Damien

0 Caro Walter over 4 years ago in reply to Damien Miliche

TI__Mastermind 19782 points

Hey Damien,

Is it possible to manage the volume control the same way that they Linux driver loads the register configuration?

So with the example I showed above, the register output would be:

w 58 00 00
w 58 7f 00
w 58 00 00
w 58 4c 20

{0x00, 0x00},
{0x7f, 0x00},
{0x00, 0x00},
{0x4c, 0x20}

All the best,
Carolina

0 Damien Miliche over 4 years ago in reply to Caro Walter

Prodigy 50 points

Hi Carolina,

that is indeed what the proposed driver is supposed to do via the tas5805m_set_volume function.

But again, all the problem is to now how to call that function from the Linux audio system, using the ALSA framework.

Kind regards,

Damien

0 Caro Walter over 4 years ago in reply to Damien Miliche

TI__Mastermind 19782 points

Hello Damien,

We do not do software support, but hopefully you will find these journals helpful:

https://www.linuxjournal.com/article/6735

https://www.kernel.org/doc/html/v4.17/sound/kernel-api/writing-an-alsa-driver.html

All the best,
Carolina

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TAS5805M: Volume control though Linux driver