15-SEP-2019 Matthew J. Wolf Email: matthew.wolf at speciosus.net

I use a PIC 16F628A microprocessor to control Twisted Pear Audio DACs
that use ESS Sabre sigma delta DAC chips. 

Twisted Pear Audio: http://www.twistedpearaudio.com

I have built three of the controllers for used with Twisted Pear Audio's:
Buffalo 32 (ES9018)
Buffalo II (ES9018)
Buffalo IIIse PRO (ES9038) 

The firmware version number does not match the hardware version.

The firmware is written in assembly language.

The controller interfaces with the Cirrus Logic CS8416 that is on a
Twisted Pear Audio i2s mux. The controller also provides control of  
the bypass line of a ASRC. 

The controller contains a i2s input switch. The switch is used to switch
between a USB i2s interface and the CS8416. The CS8416 is AES3 and S/PDIF
receiver with i2s output.

The input to the CS8416 is done via a Maxim MAX4619 multiplexer.

The controller provides uses momentary pull-up buttons: power, ASRC bypass,
input selection.  

The AC line power state of the DAC is controller via solid state relay.  

There are four leds. One led is used for the power state. There are two leds
to display the selected input. The four inputs of the CS8416 are displayed 
by a dual color led.  When the raw i2s, USB i2s, a blue led is lit. 
The fourth led is used for the ASRC bypass state.  

The functions of the controller can be accessed via RS232. The microprocessor's
UART is enabled. See the schematic diagram for the serial commands.    

The power state, selected input, and ASRC bypass state are saved to the 
microprocessor's eeprom memory. This items are restored when the