Application Note AC345
SmartFusion cSoC: Accessing EEPROM Using I2C
Table of Contents
Introduction . . . . . . . . . . . . . . .
Design Example Overview . . . . . . .
Design Example Description . . . . . .
Interface Description . . . . . . . . . .
Software Implementation . . . . . . . .
Running the Design . . . . . . . . . . .
Conclusion . . . . . . . . . . . . . . .
Appendix A – Design Files . . . . . . .
Appendix B - I2C EEPROM Driver APIs
List of Changes . . . . . . . . . . . . .
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Introduction
The SmartFusion® customizable system-on-chip (cSoC) device contains a hard embedded
microcontroller subsystem (MSS), programmable analog circuitry, and FPGA fabric consisting of logic
tiles, static random access memory (SRAM), and phase-locked loops (PLLs). The MSS consists of a 100
MHz ARM® Cortex™-M3 processor, advanced high-performance bus (AHB) matrix, system registers,
Ethernet MAC, DMA engine, real-time clock (RTC), embedded nonvolatile memory (eNVM), embedded
SRAM (eSRAM), fabric interface controller (FIC), the Philips Inter-Integrated Circuit (I2C), serial
peripheral interface (SPI), and external memory controller (EMC).
The MSS has two identical I2C peripherals that perform serial-to-parallel conversion on data originating
from serial devices, and perform parallel-to-serial conversion on data from the ARM Cortex-M3
processor to these devices. The Cortex-M3 embedded processor controls the I2C peripherals via the
Advanced Peripheral Bus (APB) interface.
The I2C peripherals in the SmartFusion cSoC device support I2C, SMBus, and PMBus data transfers,
which conform to the I2C v2.1 specification and support the SMBus v2.0 and PMBus v1.1 specifications.
The I2C peripherals can operate as either a Master or a Slave. When operating in the Master mode, the
I2C peripherals generate the serial clock and data to the Slave device that needs to be accessed. The
I2C peripherals can generate serial clock from 104 KHz to 1.66 MHz by dividing MSS clock, which can be
controlled by software. The I2C peripherals use a 7-bit addressing format and run up to 400 Kbps (Fast
mode) data rates nominally. Faster rates can be achieved depending on the external load.
Refer to the SmartFusion Microcontroller Subsystem User's Guide for more details on I2C peripherals.
This application note describes how to use the I2C interface on the SmartFusion cSoC device to access
EEPROM. A basic understanding of SmartFusion design flow is assumed. Refer to the Using UART with
a SmartFusion cSoC - Libero SoC and SoftConsole Flow Tutorial to understand the SmartFusion design
flow.
January 2013
© 2013 Microsemi Corporation
1
SmartFusion cSoC: Accessing EEPROM Using I2C
Design Example Overview
This design example demonstrates how to use I2C EEPROM on the SmartFusion Development Kit
Board. This kit has one EEPROM, ST M24512-WMN6TP, which is connected to I2C_1 on the
SmartFusion Development Kit Board. Figure 1 shows the top level interface signals used in this design
example. The UART in the MSS acts as a user interface for writing/reading string data into I2C EEPROM
through HyperTerminal.
I2C_1_SDA
MAINXIN
I2C_1_SCL
MSS_RESET
SmartFusion Microcontroller
Subsystem (MSS)
UART_0_RXD
Host PC
UART_0_TXD
Figure 1 • Top Level Interface Signals
Design Example Description
The MSS is configured to use one I2C interface (I2C_1) and one UART interface (UART_0). I2C_1 is
clocked by PCLK1 on APB bus 1 and UART_0 is clocked by PCLK0 on APB bus 0. PCLK0 and PCLK1
are derived from the clock conditioning circuit (CCC) in the MSS that generates an 80 MHz clock.
The I2C peripheral in the MSS is configured as Master which operates in Fast mode. The APB bus clock
(PCLK1) divider is set to 256 to generate 312.5 KHz serial clocks (I2C_1_SCL).
The I2C Master device initiates a read/write transaction by sending a START bit as soon as the bus
becomes free. The START bit is followed by the 7-bit serial address of the slave device and read/write
bit. The slave acknowledges receipt of its address with an acknowledge bit. When master is in Write
mode, the master sends data one byte at a time to the slave. When master is in Read mode, the slave
sends data one byte at a time to the master.
This design example uses 512 Kbit EEPROM with serial address (device select code) set to "A0" on the
SmartFusion Development Kit Board. The device select code consists of a 4-bit device type identifier
(1010b), and a 3-bit Chip Enable "Address" (E2, E1, and E0). These chip enable pins are connected to
ground (000b) in the SmartFusion Development Kit Board.
Refer to the SmartFusion Development Kit User's Guide and the ST M24512-WMN6TP datasheet for
more information on the development kit board and EEPROM specification.
The design example uses UART as a user interface for writing string data into I2C EEPROM and reading
string data from I2C EEPROM on HyperTerminal. You can enter maximum of 1 Kbyte string data through
HyperTerminal. The application writes the string data into the I2C EEPROM and reads string data from
EEPROM after the write operation that prints on the HyperTerminal.
Figure 2 on page 3 shows the string data flow from HyperTerminal to I2C EEPROM and from I2C
EEPROM to HyperTerminal.
2
Interface Description
I2C EEPROM
(Slave)
Writing
String Data
MSS (I2C Master)
HyperTerminal
Reading
String Data
Figure 2 • I2C EEPROM Read/Write Flow
Libero® System-on-Chip (SoC) projects are provided in the design files attached with this design
example.
Interface Description
Table 1 shows the top level interface signal descriptions.
Table 1 • Interface Description
Signal
Direction
Description
MSS_RESET_N
Input
Active low reset signal for the MSS.
MAINXIN
Input
Main crystal oscillator circuit.
Input to the crystal oscillator circuit. Pin for connecting an external crystal, ceramic
resonator, or RC network.
UART_0_TXD
Output
UART Transmit data
UART_0_RXD
Input
UART Receive data
I2C_1_SDA
Input
Serial data
I2C_1_SCL
Output
Serial clock
Software Implementation
The following EEPROM driver APIs are used in the example design to access I2C EEPROM.
EEPROM_init ()
This function initializes and configures the I2C peripheral for data transfer. It configures the I2C controller
with serial clock speed and EEPROM Slave address for EEPROM.
EEPROM_write ()
This function writes the content of the buffer passed as parameter to EEPROM. The data is written to the
EEPROM based on the start address and number of bytes specified. This address ranges from 0 to
EEPROM size and not the processors absolute range.
EEPROM_read ()
This function reads the content to the buffer passed as parameter to EEPROM. The data is read from the
EEPROM based on the start address and number of bytes specified. This address ranges from 0 to
EEPROM size and not the processors absolute range.
3
SmartFusion cSoC: Accessing EEPROM Using I2C
Refer to "Appendix B - I2C EEPROM Driver APIs" on page 6 for more details on I2C initialization and
configuration, and EEPROM write and read operations.
Macro Settings
The following macros to be used in EEPROM API file (EEPROM.h) to enable the communication
between I2C peripheral and EEPROM.
•
# define I2C_INSTANCE: This macro decides either I2C_0 or I2C_1 needs to be communicated
with EEPROM.
•
# define EEPROM_SLAVE_ADDRESS: This macro defines the serial address (device select
code) of EEPROM device.
•
# define EEPROM_I2C_CLK_FREQ: This macro defines the APB bus clock divider.
•
# define PAGE_SIZE_IN_BYTES: This macro defines the maximum page size in bytes. It
depends on EEPROM device. The EEPROM on the SmartFusion Development Kit Board allows
up to or 128 bytes to be written in a single Write cycle.
Refer to the SmartFusion MSS Firmware Drivers v2.0 User's Guide for more details on the I2C driver's
API.
Running the Design
Board Settings
The design example works on the SmartFusion Development Kit Board with default board settings. Refer
to the following user’s guide for default board settings.
•
SmartFusion Development Kit User’s Guide
Program the Design and Running the Application
Program the SmartFusion Development Kit Board with the generated/provided *.stp file (refer to
"Appendix A – Design Files" on page 5) using FlashPro and then power cycle the board.
Invoke the SoftConsole IDE by clicking on the Write Application code under Develop Firmware in
Libero SoC (refer to "Appendix A – Design Files" on page 5) and launch the debugger. Start
HyperTerminal with 57600 baud rate, 8 data bits, 1 stop bit, no parity, and no flow control. If your
computer does not have HyperTerminal program, use any free serial terminal emulation program like
PuTTY or Tera Term. Refer to the Configuring Serial Terminal Emulation Programs tutorial for configuring
the HyperTerminal, Tera Term, and PuTTY.
When you run the debugger in SoftConsole, the HyperTerminal window asks you to enter the string data
to be written into the I2C EEPROM.
4
Conclusion
Once you enter the string data, the application reads data from EEPROM and prints on the
HyperTerminal. Figure 3 shows the screen shot of HyperTerminal with I2C EEPROM read/write
operation.
Figure 3 • Screen Shot of HyperTerminal
Release Mode
The release mode programming file (STAPL) is also provided. Refer to the Readme.txt file included in the
programming file for more information.
Refer to the Building Executable Image in Release Mode and Loading into eNVM tutorial for more
information on building an application in release mode.
Conclusion
This application note introduces the features of SmartFusion cSoC FPGA devices and highlights the
features of I2C peripherals. The design example demonstrated the usage of I2C peripherals on
SmartFusion cSoC to access EEPROM with sample software. It also explains the usage of I2C EEPROM
driver APIs to implement EEPROM write/read operations.
Appendix A – Design Files
You can download the design files from the Microsemi SoC Products Group website:
www.microsemi.com/soc/download/rsc/?f=A2F_AC345_DF.
The design file consists of Libero SoC Verilog, SoftConsole software project, and programming files
(*.stp) for A2F500-DEV-KIT and A2F-EVAL-KIT. Refer to the Readme.txt file included in the design file for
the directory structure and description.
You can download the programming files (*.stp) in release mode from the Microsemi SoC Products
Group website: www.microsemi.com/soc/download/rsc/?f=A2F_AC345_PF.
The programming file consists of STAPL programming file (*.stp) for A2F500-DEV-KIT and A2F-EVALKIT, and a Readme.txt file.
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SmartFusion cSoC: Accessing EEPROM Using I2C
Appendix B - I2C EEPROM Driver APIs
This section describes the software driver APIs used in this design to carry out transactions with I2C
EEPROM. These drivers are included in the design files with this design example.
Function Description Of Data Structures
Enum : typedef enum
This enum represents the status of the EEPROM Read/Write. EEPROM_ADDRESS_FAULT represents
the address fault if the user provided address is out of range of the EEPROM size.
typedef enum
{
EEPROM_WRITE_SUCCESS = 0,
EEPROM_READ_SUCCESS,
EEPROM_WRITE_UNSUCCESS,
EEPROM_READ_UNSUCCESS,
EEPROM_ADDRESS_FAULT
} EEPROM_status_t;
Function Description Of Application Programming Interface (API)
void EEPROM_init (void);
This function initializes the I2C_0 and I2C_1 for data transfer, with the provided I2C clock division factor,
the slave address, and the I2C instance as macros.
EEPROM_status_t EEPROM_write (uint16_t start_address, uint16_t
size_in_bytes, uint8_t * write_buffer);
This function performs a write operation to the EEPROM based on the start address passed as first
parameter and the number of bytes passed as second parameter. If the number of bytes to be written is
more than 128 bytes, this function divides the write buffer into pages, each of 128 bytes size. Then, from
the specified start address, it writes page-by-page to the EEPROM.
•
@param start_address: The start_address parameter specifies the start address of the EEPROM,
where data has to be written.
•
@param size_in_bytes: The size_in_bytes parameter specifies the number of bytes to be written
to EEPROM from write_buffer.
•
@param write_buffer: The write_buffer parameter is a pointer to the buffer from where the data
has to be transmitted.
For example:
EEPROM_write(start_address,300,write_data);
EEPROM_status_t EEPROM_read (uint16_t start_address, uint16_t
size_in_bytes, uint8_t * read_buffer);
This function reads the content from the EEPROM. The data is read from the memory location specified
by the first parameter and number of bytes specified by the second parameter. This address ranges from
0 to EEPROM size and not the processors absolute range.
•
@param start_address: The start_address parameter specifies the start address of the EEPROM,
from where the data has to be received.
•
@param size_in_bytes: The size_in_bytes parameter specifies the number of bytes to be read
from EEPROM to read_buffer.
•
@param write_buffer: The write_buffer parameter is a pointer to the buffer from where the data
has to be transmitted.
For example:
EEPROM_read(start_address,300,read_data);
6
List of Changes
void delay_btw_transfers (volatile uint32_t n);
This function provides the delay between two I2C operations, that is, delay between stop and start
conditions. This delay can be 2 to 3 cycles of I2C serial clock.
Note: The summation of start_address and size_in_bytes should be in the range of 1 to 65536. The
start_address should be in the range of 0 to 65536 and the size_in_bytes should be in the range of
1 to 65536.
List of Changes
The following table lists critical changes that were made in each revision of the document.
Revision*
Changes
Page
Revision 4
(January 2013)
Added "Board Settings" section and "Program the Design and Running the
Application" section (SAR 43469).
4
Revision 3
(February 2012)
Removed ".zip" extension in the Design files link (SAR 36763).
5
Revision 2
(January 2012)
Modified the "Running the Design" section (SAR 35799).
4
Added the "Release Mode" section (SAR 35799).
5
Modified the "Appendix A – Design Files" section (SAR 35799).
5
Modified the section "Running the Design" (SAR 27471).
4
Modified the section "Appendix A – Design Files" (SAR 27471).
5
Revision 1
(August 2010)
Removed Table 2 • Design Files (SAR 27471).
Note: *The revision number is located in the part number after the hyphen. The part number is displayed at the bottom
of the last page of the document. The digits following the slash indicate the month and year of publication.
7
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