ADC

The ADC available gives a sampling rate of 2Msps.
We are trying to achieve this. Minimum seems to be 500ksps.

Max sampling rate  = 0.25 * operating frequency.
To get 2msps, we need 16Mhz clock, with no current limitation (CURRLIMIT = OFF).

Other important parameters  we need to see are,

Reference voltage : 1v to (Vcc-0.6)
Input range : -0.1v to Vcc+0.1v

Conversion range for differential mode(Vinp - Vinn)* : (-Vref) to (Vref)
------"------------"-----------  Single-ended-unsigned Vinp : -delV to Vref-delV
Fixed offset voltage(delV) : 190 LSB  / 0.05*Vref

*Vinp and Vinn are positive and negative inputs to the ADC.

Sampling time : 0.25 to 5us.


xmega128a3u has 2 ADC modules, connected to port A and Port B.
The ADC modules are differential by nature.

Types of input sources -
1. Differential input(without gain) :  When using in this mode, All input pins act as positive           input and pins 0 to 3 act as negative input(applicable to both portA and portB ADC)
The ADC must be in signed mode in this setting.

 2. Differential input with gain: Skip for now

3. Single-ended input :  can be done in both signed and unsigned mode.
-ve input is shorted to internal gnd in signed mode.
In unsigned mode, the voltage at -ve input is Vref*0.45

Fig 28-10 of Xmega AU manual

Thats it for now.