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Toggle switch controlled multiplexer

Question asked by RPWG on Dec 26, 2012
Latest reply on Jan 7, 2013 by BrettG

Hello all,

 

I am using the ADAU1701 in a custom circuit (active speaker). The two ADC inputs are configured as a 'balanced' analog input (internally subtracted) and I have one AES/EBU receiver feeding an ASRC which then connects to SDIN0 of the DSP for digital audio.

 

There are two toggle switches on the back of the speaker enclosure: Select analog/digital input and select digital audio channel (left/right). Here is what my Sigma Studio schematic looks like for the input selection:

 

sigmastudio.jpg

The toogle switches connect to two GPIOs (configured 'GPIO input debounce'). My intention is to control the two multiplexers SlewMux1 and SlewMux2 with these GPIOs. The two LUTs are configured as shown in the table editor. Will they output the correct index values ( '0' and '1' in 5.23 format) when driven 'HIGH' (3.3V) / 'LOW' (GND) by the toggle switches? I read somewhere that 'zero' selects the lowest index and that the highest index is selected if the input index exceeds the highest index in the table? How does the DSP interpret a logic HIGH or LOW level on the GPIOs in 28.0 format?

 

Is there a better way to achieve the multiplexer control?

 

Regards,

Roman

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