ADC voltage conversion

[Tan9890]

Hi..
I'm using ATMEGA32 in my Sound Follower project.
I'm getting a voltage of 0V to 0.7V out of my audio detection circuit..

How should i use these voltages as an input to the ADC? I mean, can the controller convert voltages having decimal points too?

Or do i need to add any new circuit? If possible, i would like to skip that step..because my hardware is completely ready..

Please give me some suggestions..

Thank You.

 

[MikeMl]

Most ADCs built in to ucontrollers are ratiometric to a voltage reference, which is typically the VDD for the chip (0 to 5V); sometimes to a built-in 2.5V voltage reference (0 to 2.5V).

You should amplify your signal so that it almost fills the full dynamic range of your ADC, whatever it says on the chip's data sheet.

 

[crutschow]

What is the form of this voltage from the audio detection circuit, AC or DC? The ATMEGA32 has an A/D converter but it can only handle positive signals from 0V to Vcc, so if the signal is AC you will have to generate a DC offset to convert the signal. Two of the differential inputs have a selectable gain of 10X and 200X.

 

[mneary]

How should i use these voltages as an input to the ADC? I mean, can the controller convert voltages having decimal points too?

The ADC gives a binary number between 0 and full scale.

You can write it as a hexadecimal or decimal number if it is convenient for you but the ADC still only gave you a binary number.

Example: If an 8-bit ADC full scale is 2.55 volts and its input is 2.55 volts, it will give you a result of 11111111. If your input is 0.7 volts the result is 01000110. If you need a human readable "0.70" your software must do it.