Amplifier input select, pre-amp and tone control

I've integrated the board into my Raspberry Pi amplifier and adjusted the code to work with the tone control board.

As you can see in the video it is working nicely! Bass treble and volume work properly and respond very quickly. I did not implement a balance control as I don't see any value in that. I've never used that in the past.

The app is still a bit hacked together as the sliders are not working properly :-/ But with some extra work it can probably be fixed rather easily.

I've started writing the software to control the board in Python. The goal is to control the board using a Raspberry Pi.

To control the board over I2C I started using the smbus2 module. It is popular for the Raspberry Pi and has good documentation.

When I started writing the software I did not notice that the TDA7439 does not support reading out its registers. So I was trying to read out the registers to see if it was working and everything just returned 1. But as the device does not support read out this is quite normal.
So then I removed all the software I wrote for read out and started testing writing to the device.

The software I've written seems to be working, but I still need to test all the functionality. For now I've only tested the input selection and the volume control. The other functions are all similar so I assume they will be working fine.

https://gitlab.com/piamplifier/python-tda7439

So today I finally got around soldering the board.
A first power-up shows that the 9 V and 3.3 V LDOs are working as expected. It also shows that I made a stupid mistake...

I added R23 in the schematic and populated it thinking that if the gate of the transistor is pulled to 3.3 V, the regulators would be disabled by default. Of course that cannot work as you cannot generate 3.3 V if you disable the regulator (duh!).
So instead either R1 has to be populated to enable all regulators by default, or an external pull-up from another 3.3 V supply needs to keep the gate high to disable the regulators.

So now that the board is soldered and the regulators are ok, I can fire up my Raspberry Pi and see if the I2C is working. Fingers crossed!

Today the board and the component arrived. The boards were produced at Aisler.

The components are one giant bag! I better start sorting them out.

The schematic and PCB design are finished. You can find everything on my GitLab page.

Currently the PCBs are in production at Aisler. They should arrive somewhere next week.
Let's hope I did not make too much mistakes!