User Manual

P A G E 16
F u s i o n f o r S T M 3 2 v 8 M a n u a l
C O N N E C T I V I T Y
INPUT / OUTPUT section
In general, I/O pins of any MCU are internally grouped as PORTs. Such pin grouping
scheme is kept throughout the development board as well, offering a clean and
organized interface.
16-BIT port
There is a total of ten 16-bit ports, labeled from PORTA to PORTJ. Ports ranging from
PORTA to PORTB are routed to the EXPANDED PORTS section (4), while ports ranging
from PORTC to PORTJ are routed to the COMPACT PORTS section (5).
EXPANDED ports
There are four distinctive EXPANDED PORTS, located at the lower left side of the board
(4), each containing a set of eight buttons, eight LEDs, a single eight-pole DIP switch,
and a single 2x5 pin header with 2.54mm pitch. These EXPANDED PORTS are labeled
according to the MCU PORT they are routed to
COMPACT ports
The lower right side of the board (5) is divided into several smaller sections, each with
a single 2x5 pin header with 2.54mm pitch, and a group of 8 LEDs. These sections are
simplified versions of the EXPANDED PORTS. The COMPACT PORT sections are labeled
according to the MCU PORT they are routed to.
PORT buttons
Port buttons can be used to apply the desired logic state to pins of the MCU PORT they
are routed to. These buttons are small tactile SPST switches that work in conjunction
with a DIP switch, labeled as BUTTONS (6) (also labeled as SW3 on the schematic –
seperatly included). This DIP switch is located in the BOARD SETUP section (7).
BUTTONS DIP switch
This four-position (poles), tri-state DIP switch, allows the button to apply a LOW logic
level to an MCU pin when pressed (connecting it to a reference GND), or to apply a
HIGH logic level when pressed (connecting it to the power rail). It can also completely
disconnect the button, preventing accidental button presses. To limit the pin current
and prevent the excessive inrush of currents when a button is pressed, a protective
220Ω resistor is used, connected in series with the switch. Each position of the
BUTTONS DIP switch is used to determine the applied logic level of a button press for
the entire PORT, there are only four poles on this DIP switch, allowing control of all four
groups of buttons.
UP position: a button applies HIGH logic level to the corresponding PORT pins
(according to 8-bit labeling)
MID position: a button is completely disconnected
LOW position: a button applies LOW logic level to the corresponding PORT pins
(according to 8-bit labeling)
UP-PULL-DOWN DIP switch
Besides the buttons, each of the four EXPANDED PORTS has a single eight-pole,
tristate DIP switch (8), labeled as UP-PULL-DOWN (SW6 through SW9 on the
schematic – seperatly included), used to enable a pull-up or a pull-down resistor for
the specific pin, or to leave the specific pin in a floating state:
UP position: connects a 4.7 kΩ resistor between the MCU power rail and the pin
associated with the particular DIP switch position (a pin is pulled-up)
MID position: disables both pull-up and pull-down resistor connections from the pin
associated with the particular DIP switch position, leaving it in a floating state
DOWN position: connects the 4.7 kΩ resistor between the GND and the pin associated
with the particular DIP switch position (a pin is pulled-down)
PORT LEDs
Each PORT contains a group of eight LEDs (9), used to visually indicate a logic state
of the specific pin. These LEDs can be found in both COMPACT PORT and EXPANDED
PORT sections. The maximum current through a single LED is limited with the 4.7k
resistor. Each LED is connected to a PORT pin and it is labeled according to the name
of the pin on the MCU.
LEDs on each PORT can be disabled, when they are not needed. Having a LED on a
communication line or an A/D converter input might alter expected results, since LED
represents an additional electrical load on a particular pin.