Atmel Xplained Evaluation Board AT32UC3L0-XPLD AT32UC3L0-XPLD Scheda Tecnica
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AT32UC3L0-XPLD
Atmel AVR32924: UC3-L0 XPLAINED Hardware User’s Guide [APPLICATION NOTE]
32156C
−AVR−06/2013
11
5.
Miscellaneous I/O
5.1
Mechanical Switch
The board is equipped with one mechanical 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.
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.
low. When done fast enough, the human eye will not see any change on the LED.
5.2
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.
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.
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.
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.
5.3
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.
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
st
order low-pass) has an approximate 3dB cut-off frequency of 160Hz. 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 1st 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.
voltage on the output of the RC filter, which can be measured on the ADC. As this is a 1st 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.