AVR32924

32156A-AVR-01/11

6 Miscellaneous I/O

6.1 Mechanical button switch

The board is equipped with one mechanical button switch. The button is shared with

LED0, and onboard protection circuitry is added to avoid a short when driving the port

high at the same time as pushing the button, which will short it to ground. To be able

to use both button and LED, time multiplexing has to be used.

To be able to detect a button press, the firmware has to periodically set the I/O pin to

input with pull-up and check if it is low. When done fast enough, the human eye will

not see any change on the LED.

6.2 LEDs

The Atmel UC3-L0 Xplained has three LEDs mounted onboard that are connected to

the Atmel AT32UC3L064. These include two standard yellow LEDs and one RGB

LED. The two yellow LEDs are active low, while the RGB LED is active high.

LED0 is shared with the mechanical button. When turning this LED on, set the I/O pin

to output low. When turning the LED off, set the I/O pin as input with pull-up. When

the LED is turned on, the protection circuitry added to the button will make the LED

shine brighter when the button is pressed. When the LED is off, any button press will

light up the LED.

One additional dual LED is mounted near the USB connector. This is the power and

status LED, which is connected to the board controller. This LED will be green when

power is applied, and will toggle between green and orange when communication

over USB is ongoing.

6.3 Analog I/O

A RC filter and an NTC are connected to ADC0 and ADC4 respectively. These analog

references can be used as input to the ADC. Both analog references can be

disconnected by cutting the cut-straps on the bottom side of the board.

The RC filter (1

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

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-L0 Xplained kit has one Atmel QTouch button and one Atmel QMatrix slider

implemented onboard. The button and the slider are connected to the built-in CAT

module in the AT32UC3L064.

The QMatrix slider can be reconfigured to be used as four separate buttons instead of

as a slider.