Digilent 410-216P User Manual

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Revision: July 16, 2011

Overview

The chipKIT Basic I/O Shield is a input/output
expansion board designed for use with chipKIT
microcontroller boards such as the Uno32™
and the Max32™.

The Basic I/O Shield is designed to provide a
range of input/output devices suitable for
beginners learning about microcontrollers and
various types of I/O devices, or for use by
more advanced user to provide inputs or
outputs for their own projects.

The Basic I/O Shield provides simple digital
input devices such as switches and buttons,
and digital output devices such as discrete
LEDs and high current open FET drivers. It
provides more advanced devices such as an
I2C EEPROM, an I2C temperature sensor, and
organic LED graphic display. A potentiometer
is also provided for use as an analog input
device.

The Basic I/O Shield is designed to the same
form factor as the Uno32 board, but is also
useable with the Max32 board.

Features:

128x32 pixel OLED graphic display
I2C temperature sensor
256Kbit I2C EEPROM
I2C daisy chain connector
4 push buttons
4 slide switches
8 discrete LEDs
4 open drain FET drivers
Analog potentiometer

1300 NE Henley Court, Suite 3

Pullman, WA 99163

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chipKIT Basic I/O Shield Reference Manual

chipKIT Basic I/O Shield Hardware Overview

The Basic I/O Shield has the following hardware features:

1) Push Buttons

Four push buttons provide momentary contact discrete digital inputs. These can be
accessed using the

digitalRead

function.

2) Slide switches

Four slide switches that provide discrete digital inputs. These can be accessed using the

digitalRead

function.

3) J2 – Shield Power Connector

This connector powers the board, receiving power from the chipKIT microcontroller board.

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chipKIT Basic I/O Shield Reference Manual

4) J3 – Analog Signal Connector

Pin 1 (analog signal A0) is connected to a potentiometer. Pins 5 and 6 (labeled as A4 and
A5) provide access to the I2C signals SDA and SCL for the I2C bus. The I2C bus is used to
access the temperature sensor and the EEPROM and for the I2C daisy chain connector.

Note: On the Uno32 it is necessary to set jumpers JP6 & JP7 to the correct position for
accessing the I2C signals on that board. On the Max32 board, it is necessary to use jumper
wires to bring the I2C signals onto the board, as the connector providing the I2C bus on the
Max32 board doesn’t contact the Basic I/O Shield.

5) Discrete LEDs

Eight LEDs that provide discrete digital outputs. These can be accessed individually using
the

digitalWrite

function. The LEDs are connected to the low eight bits of microcontroller

PORTE and all eight can be written at the same time by writing to PORTE.

6) IC2 – Temperature Sensor

This is a Microchip TCN75A digital temperature sensor. It is accessed via the I2C bus.

7) JP2/JP3 – I2C Pull-up Resistor Enable Jumpers

These jumpers are used to enable or disable the presence of the I2C pull-up resistors on
the I2C bus. Having the shorting blocks installed enables the resistors. Removing the
shorting blocks disables them.

8) J11 – I2C Daisy Chain Connector

This is a 2x4 pin header connector that provides access to the I2C signals SDA and SCL
as well as power from the 3.3V power bus and ground. This can be used to extend the I2C
bus off of the board and to power external I2C device. Digilent has cables and a selection
of I2C peripheral modules that can be accessed using this connector.

9) Potentiometer

This is a 10K ohm potentiometer connected across VCC3V3 and ground. It provides an
analog input voltage to analog input A0.

10) J1 and J2 – Digital Signal Connectors

These connectors bring digital signals from the chipKIT microcontroller board onto the
Basic I/O Shield board.

11) Organic LED Graphic Display

This is a 128x32 pixel monochrome OLED graphic display panel. This display panel is
accessed using the SPI interface.

12) J9 & J10 – Digital I/O Signal Connectors

These are screw terminal connectors that provide access to digital I/O signals 3, 5, 6, and

9. These are four of the PWM signals from the chipKIT microcontroller board.

13) J6 – Open Drain FET Power Connector

This provides access to the power connections for the open drain FETs.

14) , J7, & J8 – Open Drain FET Output

These provide access to the outputs of the open drain FETs.

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chipKIT Basic I/O Shield Reference Manual

chipKIT Basic I/O Shield Hardware Description

Introduction

The following gives a basic description of the
input/output hardware contained in the Basic
I/O Shield and how to use it. Refer to Appendix
A for a table showing pin definitions, and
Appendix B for example code to use the OLED
graphic display.

OLED Graphic Display

The Basic I/O board provides a 128x32 pixel,
Organic LED (OLED), graphic display panel.
The graphic display panel used is the
WiseChip/Univision UG-23832HSWEG04. This
display uses the Soloman Systech SSD1306
display controller.

The UG2832 has a power on/power off
sequence that should be followed. Failure to
follow the power on/power off sequence can
shorten the life of the display. The Basic I/O
provides two FETs for software control of the
two power supplies for the display. The
VDD_EN control is used to turn on/off the
power to the logic of the display. The
VBAT_EN control is used to turn on/off power
to the OLED display itself. These two pins
have pull-up resistors to turn off their
respective power supplies when not being
driven. The pin is made an output and driven
low to turn on the power supply.

Power on sequence:

Apply power to VDD
Send Display Off command
Initialize display to desired operating mode
Clear screen
Apply power to VBAT
Delay 100ms
Send Display On command

Power off sequence:

Send Display Off command
Power off VBAT
Delay 100ms
Power off VDD

The display has a D/C pin (display or
command select) that is used to determine
whether bytes sent to the display are
interpreted as commands or as display data.
The D/C pin is set HIGH for display buffer
access and LOW for command access.

The RES pin is used to reset the SG1306
display controller. The RES pin is driven LOW
for reset and driven HIGH for normal operation.
The low going reset pulse must be a minimum
of 3us (microseconds) for the display controller
to reset correctly.

The UG2832 is a serial device that is accessed
using SPI. It is however, a write-only device. It
is not possible to read back either the display
buffer contents or any kind of status from the
panel. The maximum SPI clock frequency
supported by the UG2832 is 10Mhz. Due to pin
limitations between the Basic I/O and the
Uno32 board, the select pin (SS) is wired low
on the Basic I/O board and the display is
always enabled to receive data over the SPI
interface.

Digilent has a library for use with the Basic I/O
that provides functions for initializing the
display and rendering simple text and graphics
onto the display. This library can be used as-is
or as a starting point for a more sophisticated
graphics library. This library is available on the
Digilent web site and in the third part libraries
repository on github.

Appendix B provides example code that shows
initializing the display and writing to it.

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chipKIT Basic I/O Shield Reference Manual

Discrete Digital I/O Devices

The Basic I/O Shield provides various discrete
digital I/O devices. These can be accessed

using the
functions. The

the pin to input or output.

When the buttons and switches on the Basic
I/O are not being used, the pins are available
on the pass-through shield connectors for use
by other shields in the stack. The pins used by
the LEDs are also available, however the
presence of the LEDs on the lines will load
them down, possibly causing some devices to
not work. It is safe to use any of these pins as
either inputs or outputs.

Push Buttons: There are four push buttons
switches labeled BTN1 (pin 4), BTN2 (pin 34),
BTN3 (pin 36), and BTN4 (pin 37). The

digitalRead

button is not pressed and
button is pressed.

Slide Switches: There are four slide switches
labeled SW1 (pin 2), SW2 (pin 7), SW3 (pin 8)

and SW4 (pin 35). The
return
the push buttons) and

up (toward the OLED display).

LEDs: There are eight LEDs, labeled LD1 –
LD8 accessed as digital pins 33 – 26. An LED
will be illuminated when the corresponding pin

is set to the
function and off when set to the

The LEDs are attached to the low eight bits of
PORTE, with LD1 connected to PORTE bit 0,
and LD8 connected to PORTE bit 7. An 8-bit
value written to PORTE (or LATE) will display
the corresponding binary value on the LEDs.

digitalRead

function will return

and

pinMode

digitalWrite

function is used to set

LOW

HIGH

when the

digitalRead

LOW

when the switch is down (toward

HIGH

when the switch is

HIGH

state using the

digitalWrite

LOW

if the

function will

state.

Open Drain FET Outputs

The Basic I/O provides four open drain FET
outputs. These are low-side N-channel devices
and can be used to provide a digital switch

closure to ground. These can be used to
switch external loads, such as relay coils,
solenoids, stepper motors, and so on.

The FETs used are the NTHD4508N. These
FETs are rated for a maximum VDS (voltage
from drain to source) of 20V. They are rated for
a maximum continuous current of 3.0A at 25ºC
and 2.2A at 85ºC. For more detailed
specifications for the FETs refer to the data
sheet available from the On Semiconductor
web site.

The FETs are labeled Q1A (pin 9), Q1B (pin

6), Q2A (pin 5), and Q2B (pin 3). These four
pins are also four of the PWM outputs
supported by the chipKIT boards and the FETs
can be switched using pulse width modulation

(PWM) using the

An FET is switched on by driving its gate high.
When the FET is on, it provides a low
impedance path to ground (similar to a closed
switch to ground). When the FET is switched
off by driving its gate low, it becomes a high
impedance path to ground (similar to an open
switch to ground). Pull-down resistors are
connected to the gate of each FET to ensure
that it is off unless being actively driven high by
the microcontroller on the chipKIT board.

The FET outputs are accessed via the screw
terminal connectors J7 and J8 on the left side
of the board. The digital signals used to switch
the FETs on and off are also available on
screw terminal connectors J9 and J10 at the
left side of the upper edge of the board.

A FET is used to switch an external load, such
as a relay coil, on and off. The load is wired
between the positive side of an external power
supply and the output of the FET. When the
FET is switched on, current will flow from the
external power supply through the load and the
FET to ground.

FETs are often used to switch highly inductive
loads, such as relay coils, solenoids, and
motors. When the current through an inductive
load is switched off, a voltage spike will occur

analogWrite

function.

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