Digilent 410-216P-KIT - Manual (Page 6)

chipKIT Basic I/O Shield Reference Manual
www.digilentinc.com page 6 of 15
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that can damage the FET. The Basic I/O
provides clamp diodes (also called snubber or
flyback diodes) to clamp the voltage spike and
feed the current back to the external supply.
Screw terminal connector J6 is used to provide
the power and ground connections back to the
external power supply. The negative (-) pin of
J6 connects the external supply ground with
the Basic I/O ground, and the positive (+)
terminal connects the Basic I/O to the external
supply voltage.
The unloaded two pin header JP1 can be used
to connect the board VCC5V0 power supply
bus to the external power supply bus so that
the board 5V supply can be used instead of an
external supply. In this case, J6 is used to
connect the board supply to the external loads.
If this is done, the total current consumed by all
external loads must not exceed 2A or the
current rating of the board power supply
(whichever is less).
I
2
C Bus
The I
2 C bus from the chipKIT microcontroller
board is brought onto the Basic I/O Shield.
There are two I
2 C devices on the board and a
connector for taking the I 2 C bus off of the
board to connect to additional external I 2 C
devices.
I
2 C Connector: Connector J11 can be used to
extend the I 2 C bus off of the board to connect
to additional external I 2 C devices. J11 is a
standard 2x4 pin header connector with 0.100”
spaced pins. It provides access to the I
2 C
signals, SCL and SDA, plus VCC3V3 and
ground. The VCC3V3 can be used to power
external I
2 C devices.
The I
2 C bus uses open collector drivers to
allow multiple devices to drive the bus signals.
This means that pull-up resistors must be
provided to supply the logic high state for the
signals. The Basic I/O provides 2.2Kohm pull-
up resistors. Generally, only one set of pull-up
resistors are used on the bus. Jumpers JP2
and JP3 can be used to disable the on-board
pull-up resistors if a different value is needed
or some other device on the bus is providing
the pull-ups. The on-board pull-up resistors are
enabled by install shorting blocks on JP2 and
JP3. Removing the shorting blocks disables
the pull-up resistors.
Digilent has several small I/O modules
available that can be connected using the I
2 C
connector. These include a 3-axis
accelerometer, 4-channel, 12-bit A/D
converter, serial character LCD panel, 3-axis
gyroscope, real-time clock/calendar, and I/O
expander.
EEPROM: A 256Kbit (32Kbyte), I
2 C EEPROM
is provided using a Microchip 24LC256. This
EEPROM, IC1, is located on the bottom left of
the board, just below the chipKIT logo.
The seven bit I
2 C device address for the
EEPROM is ‘1010000’.
Digilent provides a library for accessing this
EEPROM. The library is available on the
Digilent web site and in the third party libraries
repository on github.
For complete technical documentation on the
24LC256, refer to the data sheet available on
the Microchip web site.
Temperature Sensor: A digital temperature
sensor is provided using a Microchip TCN75A
2-Wire Serial Temperature Sensor. The
temperature sensor, IC2, is an I
2
C device, and
is located in the lower right corner of the board.
The TCN75A is rated for an accuracy of +/-1ºC
and has selectable resolution from 0.5ºC down
to 0.0625ºC. The seven bit device address is
‘1001000’.
Digilent provides a library for accessing the
temperature sensor. This library is available on
the Digilent web site and in the third party
library repository on github.
The TCN75A provides an alert output that can
be programmed for various functions. This