The ‘RST’ pin can be used to restart the Fio. This pin is pulled high by a
10kΩ resistor on the board, and is active-low, so it must be connected to
ground to initiate a reset. The Fio will remain off until the reset line is pulled
back to high.
I/O Pins
Many of the Fio’s I/O pins are multi-talented. Every pin can be used as a
digital input or output, for blinking LEDs or reading button presses. These
pins are referenced in the Arduino IDE via an integer value between 0 and
23. (The A0-A10 pins can be referenced digitally via either their analog pin
number or digital pin number).
Eleven pins feature analog to digital converters (ADCs) and can be used as
analog inputs. These are useful for reading potentiometers or other analog
devices using the
analogRead([pin]) function.
There are six pins with pulse width modulation (PWM) functionality, which
allows for a form of analog output using the
analogWrite([pin], [value]) function. These pins are indicated on-board
with a faint white circle around the pin.
There are also hardware UART (serial), I C, and SPI pins available. These
can be used to interface with digital devices like serial LCDs, IMUs, and
other serial sensors.
The Fio v3 has five external interrupts, which allow you to instantly trigger a
function when a pin goes either high or low (or both). If you attach an
interrupt to an interrupt-enabled pin, you’ll need to know the specific
interrupt that pin triggers: pin 3 maps to interrupt 0, pin 2 is interrupt 1, pin 0
is interrupt 2, pin 1 is interrupt 3, and pin 7 is interrupt 4.
On-Board LEDs
There are a variety of LEDs on the Fio, the simplest of which is the red
power indicator. Two LEDs towards the bottom – labeled RX and TX – help
indicate when data is transferring to and from the Fio through USB. A blue
LED represents USB data coming into (‘RX’) the the Pro Micro, and a
yellow LED indicates USB data going out (‘TX’).
There are three LEDs tied to the XBee interface in particular: stat, RSSI,
and associate. The red LED labeled ‘ON’ is connected to the XBee’s pin 13
– DIO9 – which is, by default, set to indicate the XBee module’s ON/OFF
status. An ‘RSSI’ LED connects to XBee pin 6 (PWM0) which defaults to
indicate RSSI (received signal strength) – a brighter LED means a stronger
received signal. Lastly, the ‘ASO’ LED connects to XBee pin 15, which will
blink if the module is associated.
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