Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK Data Sheet

 897

SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

In the same way, a minimal Sample and Hold Time is necessary for the TSADCC to guarantee the best converted
final value between selection of two channels. This time depends on the input impedance of the analog input, but
also on the output impedance of the driver providing the signal to the analog input, as there is no input buffer
amplifier.

The Sample and Hold time has to be programmed through the bitfields SHTIM in the 

. 

The field SHTIM defines the number of ADC Clock cycles for an analog input, while the field TSSHTIM defines the
number of ADC Clock cycles for a Touch Screen input.

These both fields can define a Sample and Hold time between 1 and 16 ADC Clock cycles.

The field TSSHTIM defines also the time the power switches of the Touch Screen are closed when the TSADCC
performs a conversion for the Touch Screen.

A resistive touch screen is based on two resistive films, each one being fitted with a pair of electrodes, placed at
the top and bottom on one film, and on the right and left on the other. Between the two, there is a layer that acts as
an insulator, but also enables contact when you press the screen. This is illustrated in 

The TSADC controller has the ability to perform without external components:

• Position Measurement

• Pressure Measurement

• Pen Detection

Touch Screen Position Measurement

X

M

X

P

Y

M

Y

P

X

P

X

M

Y

P

VDD

GND

Volt

Horizontal Position Detection

Y

P

Y

M

X

P

VDD

GND

Volt

Vertical Position Detection

Pen 

Contact