ADC chip  to one of the GPIO

Can I add a ADC chip  to one of the GPIO pins of the ADAU1701 to get more analog inputs on the ADAU1701 ?

I want to add more analog inputs to the ADAU1701 to control pots and switches would this work ?

Thanks in advance

  • Hello Hopeton,

    The ADAU1701 contains a 4-channel auxiliary 8-bit ADC which you can connect up to external control pots for volume and tone control.  Refer to page 45 in the datasheet.

    The EVAL-ADAU1701MINIZ board contains a potentiometer connected to AUX_ADC3.  Here is an example for a simple volume control using that input.   For more info on using ADC and GPIO inputs, see AN-951

    -JT

  • I forgot to mention the example project above uses the Single Slew External Volume Cell controlled by ADC3 input.  See: Single Slew External Volume [Analog Devices Wiki]

    -JT

  • Thanks , I was meaning in addition to the 4 ADC that is built in the ADAU1701, use an external ADC  on one of the digital input pins to receive signal from  ADC so I can have 4 more ADC i.e.

  • Hello Hopeton,

    Thank you for the clarification.   Looking at the datasheet, it would not be possible to implement such an interface with just regular GPIO functionality.

    Considering the MPx serial port pins, it might be possible to use the I2S serial ports to interface to the MAX1110, as long as you are not already using the serial port to interface to a host processor.   Looking at the serial port timing on page 16 in the Maxim datasheet, it looks like it can implement a 16-bit pulsed DSP serial mode interface.  The ADAU1701 supports pulse serial mode and you can also set up a data word size of 16-bits, and invert the frame sync pulse to be active low by switching the LRCLK polarity bit in the serial port registers.

    However, it seems data transactions do not begin to transmit ADC data until it receives a control byte from the ADAU1701.  This would be very tricky (if not impossible to synchronize) from the SigmaStudio sample-by-sample processing signal flow, so I would say interfacing to such a device to the ADAU1701 cannot be done without some sort of interface logic or host microcontroller to transmit data to the ADAU1701 as I2S ADC data.

    -JT