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USER MANUAL FOR HARDWARE REV 3.11
07-APR-2018
PAGE 8
3.4
ANALOG TO DIGITAL CONVERTER
A MCP3208 is built into the system to provide
analog input capabilities with support for 8
channels with 12-bit resolution per channel.
Each channel is provided with some input
protection through a current limiting resistor
and a Zener diode. It is the user’s responsibility
to ensure the inputs are not over driven beyond
a 5V maximum input voltage to prevent damage
to the ADC unit.
Channel A0 has a unique configuration to allow
for the use of a LM335 temperature sensor
device. It is recommended to use this channel
last to minimize potential confusion due to the
unique configuration.
3.5
GPIO EXPANSION
As the repeater board consumes most of the
signals from the 40 pin header, an additional 8
pins are made available through a 16 pin header.
This header connects to PORT A on a MCP23017
IC, and provides input circuit protection through
Zener diodes which limit the input voltage to
3.5V maximum.
Caution should be exercised to ensure only
3.3V
logic levels
are used to connect to these pins.
The GPIO expander provides the option to
include pull-up resistors should your circuit need
these, but are not turned on by default, you will
be responsible for configuration of these pins if used.
Connector Selection: Due to the tight spacing of the board, it is important to select mating connectors
that do not exceed the width of the male pin alignment blocks, or you risk mechanical interference with
the port 2 header. For custom cables we suggest using connector block
952-2037-ND from Digikey
, or a
similar variant.
STANDARD IDC RIBBON CABLE CONNECTORS WILL NOT FIT.
