DAC & SPDIF joined

I’m currently working on my own DAC board for Pi with volumio, I already got working WM8804 and PCM5122 working simultaneously and outputting SPDIF and analog signal the same time. WM8804 is working as i2S master and master clock generator, PCM5122 is I2S slave. It works using driver from HIFI Berry Digi. My next steps will be adding an I2C control for PCM5122 to better set conversion modes and possible use of another chips like PCM1796 and PCM1794, and tray out additional PLL chip between WM8804 and DAC to additionally clean master-clock. I’m electronic engineer and assembler programmer, but lack any experience with Linux, I like to implement volume control to DAC from Volumio, but not want to use driver from HIFIBerryDAC+ (PCM5122), because it works with Pi as I2S master. If I can get any help how to get volume control data from Volumio to I2C address I will be very interested in such information.
dac1.JPG

Charly,
I have some other homebrew I2S equipment, so I wanted to hook up something to my new Pi 2. I am interested in the WM8804. Did you connect I2C to the Pi and tell Volumio that it was a Digi?

Jake

You need to setup WM8804 for I2s control (2 wire) and address 0x76/0x77 (pin 5=high), connect I2s to GPIO pins 2,3 (don’t forget pullup resistors), and I2S according to header pinout (you must have 22-33R resistors in I2S wires to prevent ringing). It works with Hifiberry Digi driver. WM8804 must have 27mhz crystal connected and it will work as i2s master and generate Master clock on pin 16. You can use I2S an generated MCLK to drive additional DAC, but keep all wires very short and make a good ground plane or it will not work. Masterclock will be 256fs if fs<96khz and 128fs if higher. I tested another version with added PLL for MCLK cleanup, and liked its sound very much, but I need to test both configurations on real PCB, to objective tell if there is a difference, because additional jitter might be brought in by long connections.

Charly,
Thanks for your input - it did help in the design and debugging.
You can see my project in a new thread https://volumio.org/forum/homebrew-digi-t3170.html

Jake