MattairTech MT-DB-U4, User Manual

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MT-DB-U4 User Guide
Pin Descriptions
Pin Description
Gnd Digital ground
5V, Vbus 5V output from USB Vbus. Vbus pin is tied to 5V pin. These pins are
connected to the Vbus and UVcc pins of the microcontroller.
Vcc Voltage input pin. Use solder jumper J1 to connect this pin to 5V (default
setting) when using USB power. In this case, Vcc is an output. Leave J1
unconnected to supply power from an external source to the Vcc pin. This
pin is connected to the Vcc and AVcc pins on the microcontroller, as well
as the ISP header and reset pullup. See Power Configuration Section.
3.3V 3.3V output from the microcontrollers internal 3.3V regulator. This pin is
connected to Ucap on the microcontroller.
Avcc Voltage input to the analog section of the microcontroller. This pin is
connected to Vcc through a 10uH inductor and 100nF capacitor and
provides power to the microcontroller analog section (Avcc pin).
Aref Voltage input. This is the reference voltage used by the ADC in the
microcontroller.
DO NOT
connect if using an internal reference.
Agnd Analog ground
RST Connects to reset pin of microcontroller as well as the reset button. A 10K
pullup resistor and 100nF capacitor are connected to this pin.
E2 / B (Boot) This pin is connected to the HWB jumper. The jumper is connected to
ground through a 240 ohm resistor. The pin is sampled after all reset
sources, including power­up. If the pin is low (HWB jumper installed), then
the bootloader is run. If the pin is high (HWB jumper removed), then the
user application is run. This pin functions as a normal GPIO pin at all other
times. The 240 ohm resistor provides short­circuit protection in case the
pin is used as an output and the jumper is installed.
D7 / L (LED) The green status LED is connected to this pin. The LED is connected to
ground through a 240 ohm resistor. Drive the pin high to turn on the LED.
It can be disconnected by cutting the solder jumper trace (Rev B only).
xtal1 This pin is connected to the on­board 16MHz crystal. If using an external
clock, connect it to this pin, connect the solder jumper (Rev B only), and
configure the microcontroller fuses to use an external clock. This is also
useful for HV programming or recovery from incorrectly set fuses.
xtal2 This pin is connected to the on­board 16MHz crystal. This pin is useful
along with xtal1 to connect an external crystal. Board revision B has a
solder jumper to connect this to the external header pin.
E6, F0, F1, F4, F5, F6,
F7 These are generally used as analog pins. Analog ground plane runs under
these pins. Consult datasheet for functionality.
All other pins Consult datasheet for functionality.
December 30, 2015 9 http://www.mattairtech.com/