how to impliment 4*1 multiplex in ADAU1701?

Hello vishnu_riosh,

Here is a project that does what you asked for.

It uses a brute force direct method of translating the 5.23 input from a GPIO and weighting each bit and adding them together to produce a 28.0 number that counts from 0-3.

This program works on the mini eval board.

I also have another idea that I will post in a few minutes.

There are always many ways to do things.

Dave T

Well, my other idea was to use a 2-dimentional table but it takes a 28.0 input and then outputs a 5.23 number so you would have to convert the GPIO going into the table and then convert the output back to a 28.0 number so that would negate the instructions savings of a 2-dimentional table. It would be great if it had the integer/float button that are on other tables. That would be a good suggestion.

So for now the above solution will work for you.

Dave T

Hello vishnu_riosh,

I do not think you can directly connect a microphone to the ADC of ADAU1701, reading the datasheet, these are line inputs.

I think first you have to preamp the microphone signal for example with an SSM2167.
Then maybe Dave has a better solution.

hi Deve Thib, Thanks for your reply. now i will try the above solution. As per attachment we connected microphone to ADAU1701. But, output side we are getting small sound. How can we improve volume? is there any programming method is there to improve volume?

Hello Vishnu_riosh,

piero is correct that the best way is to amplify the microphone signal before bringing it into the ADC. With this part there is some control of the input full-scale voltage but it will not give you enough gain. Look at table 13 in the datasheet where it shows the full scale voltage for different input resistors. So you can get a little more gain but performance will start to suffer so an external preamp is the best way to go.

Dave T

Hi Dave Thib,

Thanks for your reply. By using an external preamplifier the issue is resolved. We took long time for resolving this issue. Once again thanks!

Hi Dave Thib,

While speaking through microphone we are facing a feedback problem. How to control this microphone feedback with speakers? Please help to resolve the problem.

Hello Vishnu_riosh,

What is your application?

How many inputs and how many outputs?

How far away from the speaker is the microphone?

Is the distance fixed?

Is there some sort of two-way communication with a remote person? If so then does it have to be full-duplex or can it be half duplex?

Dave T

Hi Dave Thib,

Thanks for your continues help. Please find the following details

1. Application: Simple Voice Processing
2. 1 Input (Microphone) and 3 Outputs (1 Speaker, 2 Transducers)
3. Yes, Distance fixed (10 Inches)
4. One way communication, Simplex

Regards,
Vishnu