8

AVR32918

32159A-AVR-01/11

6 Miscellaneous I/O

6.1 Mechanical button

The board is equipped with one mechanical button. Because the button is used to

enter bootloader mode it has a pull-up mounted, this means it is not necessary to use

the pull-up in the UC3 to detect the status of the button.

6.2 LEDs

The Atmel UC3-A3 XPLAINED has four yellow LEDs which are connected to the

Atmel AT32UC3A3256 and all of them are active low.

One dual LED is mounted near the USB connector. It has one green LED which is

used to indicate power and one red LED that can be used for other purposes. The

green LED will be active when power is applied to the board but it can be disabled by

software from the AT32UC3A3256 device if needed. The red LED is active low and

the green LED is active high.

6.3 Analog I/O

A RC filter and a NTC temperature sensor are connected to ADC0 and ADC1

respectively. These analog sensors are used as input to the ADC but it is also

possible to disconnect them by cutting the cut-straps on the bottom side of the board.

The RC filter (1. order low-pass) has an approximate 3dB cut-off frequency of 159Hz.

The input to the RC filter is one of the UC3 GPIO pins that can be configured to

output a PWM signal to the RC filter. This can be used to generate a DC voltage on

the output of the RC filter which can be measured on the ADC. As this is a 1. order

filter, the ripple on the DC voltage is proportional to the input frequency. A higher

input frequency will give lower ripple on the output.

6.4 Touch

The UC3-A3 XPLAINED kit has one QTouch button and one QTouch slider; both are

connected to GPIO pins on the AT32UC3A3256.

Table 6-1. UC3 touch connections.

Touch sensor

onboard reference

QTouch method pin name

UC3 GPIO pin

CH1

SNSK1

98

CH1

SNS1

99

CH2

SNSK2

100

CH2

SNS2

101

CH3

SNSK3

102

CH3

SNS3

103

CH4

SNSK4

104

CH4

SNS4

105