Infineon I2C Read Ext Device 1 User manual

AURIX™ TC2xx Microcontroller Training
V1.0.0
I2C_Read_Ext_Device_1
Read external device MAC address via I2C
Please read the Important Notice and Warnings at the end of this document

Scope of work
An I2C module configured as I2C master is used to read a register of an
external device.
An I2C module configured as I2C master is used to read the MAC address
stored in MCP79411, a Real-Time-Clock device mounted on the board
KIT_AURIX_TC297_TFT_BC-Step. The AURIX™ device reads the MAC
address through the I2C module and stores it into a global variable.
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2019-10-17 Copyright © Infineon Technologies AG 2019. All rights reserved.

Introduction
›The I2C protocol was developed to provide a simple and efficient data
transfer between multiple devices over a short distance.
›It uses a bidirectional serial bus with two wires. A serial data line (SDA)
and a serial clock line (SCL) are carrying the information between multiple
devices.
›Both lines are connected to a positive supply voltage via pull-up resistors.
›An I2C device can work as a master or as a slave. The master, which is
normally a microcontroller, initiates and terminates the transfer and
generates the clock pulse.
›A specific slave can be addressed by the master via a 7- or 10-bit
address. Afterwards the master starts the communication.
–Data can flow in either direction and can be set via a data direction bit,
which is transmitted by the master.
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Hardware setup
This code example has been
developed for the board
KIT_AURIX_TC297_TFT_BC-Step
The MCP79411 chip is mounted on
the board and connected via the I2C
bus to the microcontroller.
The used data lines are connected to
the positive power supply via two
pull-up resistors.
The MCP79411 is a battery-backed
I2C Real-Time Clock/Calendar
(RTCC) device with SRAM,
EEPROM and protected EEPROM.
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Implementation
Configuring the I2C communication
The configuration of the I2C communication is done once in the setup phase
in two different steps:
›The initialization of the I2C module by initializing an instance of the
IfxI2c_I2c_Config structure
›The initialization of every device that is connected to the I2C module (in this
case, the MCP79411 chip) by initializing an instance of the
IfxI2c_I2c_deviceConfig structure for each device
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Implementation
Configuring the I2C module
The function IfxI2c_I2c_initConfig() initializes an instance of the structure
IfxI2c_I2c_Config with its default values.
The IfxI2c_I2c_Config structure allows setting the parameters to initialize the
module:
›baudrate –to set the clock speed in bit/s. Typical values are 100 kbit/s in
standard mode, 400 kbit/s in fast mode and 3.4 Mbit/s in high-speed mode.
›pins –a structure to set the port pins used for the communication.
A serial data line (SDA) and a serial clock line (SCL) carry the information
between the devices, therefore two port pins are required.
The function IfxI2c_I2c_initModule() initializes and activates the I2C module
with the user configuration in master mode.
The functions above are provided by the iLLD header IfxI2c_I2c.h.
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Implementation
Configuring the I2C device
The function IfxI2c_I2c_initDeviceConfig() initializes an instance of the
structure IfxI2c_I2c_deviceConfig with its default values.
Afterwards, the 7-bit slave address can be set through the parameter
deviceAddress.
The function IfxI2c_I2c_initDevice() finalizes the I2C initialization by connecting
the device configuration with the preconfigured I2C module.
The functions above are provided by the iLLD header IfxI2c_I2c.h.
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Implementation
Establish I2C communication
Data transfer between the external device and the microcontroller is
divided into two steps:
›Firstly, the microcontroller is transmitting the address of the register, in which
the requested data is stored on the external device (the register containing
the MAC address of MCP79411 is 0xF2). This is done using the
IfxI2c_I2c_write() function.
›Then, the reading of the MAC address is started with the function
IfxI2c_I2c_read().
Both the write and read functions are defined in the iLLD header IfxI2c_I2c.h.
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Run and Test
After code compilation and flashing the device, perform the following steps:
›Use the debugger to watch the hexadecimal value of the
global array g_macAddr. The MAC address is unique for each board.
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Run and Test
›A second test can be performed with
an oscilloscope. Two oscilloscope
probes can be connected to SDA and
SCL pins to observe the generated
and received signals.
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