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====== I2C(CUNET) ======

CUNET is a communication protocol for CUBLOC peripherals such as the
CLCD, GHLCD, CSG modules. (CUNET is the same as I<sup>2</sup>C)

With just 2 pins, SCL and SDA, up to 127 devices can be communicated with simultaneously. CUNET uses CUBLOC’s
I2C protocol to perform the communication.

To use CUNET, please be sure to add pull up resistors(4.7K each) to the SCL
and SDA lines. SCL and SDA pins are in an open-collector configuration,
protecting against outside noise. It automatically removes pulses less than
50ns.

{{ :CUBLOC:i2c_cunet_interface:cunet1.png?nolink |}}

When using CUNET, the connector’s pin 1 must be connected to ground, pin
2 to 5V or RESET, pin 3 to SCL, and pin 4 to SDA. This 4 pin configuration
is standard for all CUNET interfaces.

When using CUNET, the CUBLOC core module will act as the master and the
connected device will act as as the slave. All CUNET devices will respond to
the CUBLOC while in an idle state.

CUNET is a master-slave protocol. Slaves cannot initiate communication
with the master. For externally-initiated communication, you must use PAD
communication. PAD can receive inputs from other external devices without
the need for the CUBLOC to initiate communication. Please refer to the On
Pad command for more detailed information.

When the device is to be powered from the CUNET bus, pin 2 of the CUNET
device should be connected to 5V on the main module:

{{ :CUBLOC:i2c_cunet_interface:cunet2.png?nolink |}}

Pin 2 of a CUNET device can be connected to RESET on the main module
when a separate power supply is powering the CUNET device. (Active-low
to RESET causes the CUBLOC to reset)

{{ :CUBLOC:i2c_cunet_interface:cunet3.png?nolink |}}

CUNET cables can be up to 3 feet in length. For longer distances (up to
approximately 1 mile), the Phillips I2C long distance interface chip (P82B96
or P82B715) can be used.