Preface; Introduction To I²C; Operation Of I²C - DEICO ONYX DE4001 User Manual

PREFACE

This manual describes the usage of Onyx USB I²C/SPI Converter and graphical user interface
(GUI). Onyx I²C/SPI Adapter can be controlled using the provided graphical user interface
(GUI).
Introduction to I²C
Inter-Integrated Circuit (I²C) is a synchronous serial communication protocol. All devices are
connected via 2-wires that are Serial Data (SDA) and Serial Clock (SCL). I²C has a master/slave
protocol and it supports multi master and multi slave operations. Every slave device has its
own unique address.
Operation of I²C
In I²C, data is transferred by message. Messages are broken up into frames. Each message has
an address frame and one or more data frame. Messages have also start bit, stop bit,
read/write bit and ack/nack bits. Message frame is shown in
shown in Figure 3.
7 OR 10 BIT
START
SLAVE
CONDITION
ADDRESS
 Start Condition: SDA line switches from high to low before SCL line switches from high
to low.
 Address Frame: The address frame is always first in any new communication
sequence. Each slave has a 7 or 10 bit unique address.
DE4001_USER MANUAL
Rev. No:0 Rev. Date: 05.08.2023
Figure 1: Onyx USB-I²C/SPI Converter
READ/ ACK/
8 BIT DATA
WRITE NACK
FRAME
BIT BIT
Figure 2: Message frame of I²C
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Figure 2 and sample bitstream is
ACK/ ACK/
8 BIT DATA
NACK NACK
FRAME
BIT BIT
STOP
CONDITION
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