How to use I2. C bus on the Atmel AVR Microcontroller. I2. C read as I Squared C bus first introduced by Philips in 1. I2. C bus has become one of the most important microcontroller bus system used for interfacing various IC devices with the microcontroller. The I2. C bus use only 2 bidirectional data lines for communicating with the microcontroller and the I2. C protocol specification can support up to 1. Today many I2. C IC devices available on the market such as Serial EEPROM, IO Expander, Real Time Clock, Digital to Analog Converter, Analog to Digital Converter, Temperature Sensor and many more. The I2. C protocol use master and slave method, the master which is usually the microcontroller while the slave can be any I2. C devices such as Serial EEPROM, IO Expander or even another microcontroller. All of these devices connected to the I2. C bus one for the serial data called SDA serial data and the other for synchronize clock called SCL serial clock each of these slave devices has their own individual 7 bits of the address length. The 7 bits address consists of 4 bits device identification and 3 bits device physical address. For example if we want to use the Microchip 2. AA1. 28 I2. C CMOS serial EEPROM, the first 4 bits for this device identification is 1. A0, A1 and A2 on the serial EEPROM. Therefore by using these 3 bits we could attach up to 8 Microchip 2. AA1. 28 serial EEPROM on the same I2. C bus which give you total of 8 x 1. Kbytes of memory. KOwXIV8LtO4/VO408aCBBII/AAAAAAAAFH8/fO4gQxEn59o/s1600/scr1.png' alt='Avr Gcc Program Memory' title='Avr Gcc Program Memory' />Avr Gcc Program Memory MirrorsThe same principal also applies to the other I2. C bus devices such as the Microchip MCP2. IO Expander and Dalas DS1. Real Time Clock see the example picture. By selecting the appropriate device address, the master can easily communicate with the entire slave devices connected to the I2. C bus the I2. C bus protocol only allowed one connection to be established between master and slave at a time. With this powerful and yet simple concept you could see the enormous possibility of using these I2. C bus devices for the embedded application. In this tutorial we will use the AVRJazz Mega. Microchip 2. 4AA1. I2. C serial EEPROM on the board we will use this EEPROM for storing the LEDs data pattern and later on we will read the data and display it to the LEDs attached to the AVR ATMega. PORT D. The principal we learn on this I2. C serial EEPROM device can be applied to other I2. C devices as well, the differences is only on the terms used on the serial EEPROM we use memory address for storing and retrieving the data, while on the other I2. Avr Gcc Program Memory' title='Avr Gcc Program Memory' />Gcc Unix, Linux Command Manual Pages Manpages, Learning fundamentals of UNIX and Linux in simple and easy steps A beginners tutorial containing complete. SmartPCFixer is a fully featured and easytouse system optimization suite. With it, you can clean windows registry, remove cache files, fix errors, defrag disk. C devices such as Microchip MCP2. IO expander or Dalas DS1. Real Time Clock we use register address for writing and reading the data. The following is the list of hardware and software used in this tutorial AVRJazz Mega. AVR ATmega. 16. 8 microcontroller board schema. Win. AVR for the GNUs C compiler. Atmel AVR Studio 4 for the coding and debugging environment. STK5. 00 programmer from AVR Studio 4, using the AVRJazz Mega. STK5. 00 v. 2. 0 bootloader facility. Atmel AVR ATMega. Datasheet. Now lets jump to the C code that make this happen. File Name i. 2cbus. Version 1. 0. Description I2. Cbus EEPROM AVR Microcontroller Interface. Authors RWB. Targets AVRJazz Mega. Learning Board. Compiler AVR GCC 4. Win. AVR 2. 00. 80. IDE Atmel AVR Studio 4. Programmer AVRJazz Mega. STK5. 00 v. 2. 0 Bootloader. AVR Visual Studio 4. AVRGCC Source Examples. The following example programs, which I have developed, are written in C for use with the AVRGCC compiler. Tested with AVRGCC WinAVR. STK5. 00 programmer. Last Updated 2. Dec 2. Headhunters Gang Patch. MAXTRIES 5. 0define EEPROMID 0x. A0 I2. C 2. AA1. 28 EEPROM Device Identifier. EEPROMADDR 0x. 00 I2. C 2. 4AA1. 28 EEPROM Device Addressdefine I2. CSTART 0. define I2. Avr Gcc Program Memory SeatCDATA 1. I2. CSTOP 2unsigned char i. I2. CSTART Send Start Condition. TWCR 1 lt lt TWINT 1 lt lt TWSTA 1 lt lt TWEN. JdoYjE9_84w/UnpQrf_Cx1I/AAAAAAAABXc/tWON5oyf52Y/s1600/GUI.png' alt='Avr Gcc Program Memory Map' title='Avr Gcc Program Memory Map' />I2. CDATA Send Data. TWCR 1 lt lt TWINT 1 lt lt TWEN. I2. CSTOP Send Stop Condition. TWCR 1 lt lt TWINT 1 lt lt TWEN 1 lt lt TWSTO. Wait for TWINT flag set in TWCR Register. TWCR 1 lt lt TWINT Return TWI Status Register, mask the prescaler bits TWPS1,TWPS0. TWSR 0x. F8. MAXTRIES return rval Transmit Start Condition. I2. CSTART. Check the TWI Status. TWMTARBLOST goto i. TWSTART twistatus TWREPSTART goto i. Send slave address SLAW. TWDR devid 0x. F0 devaddr 0x. TWWRITE Transmit I2. C Data. twistatusi. I2. CDATA Check the TWSR status. TWMTSLANACK twistatus TWMTARBLOST goto i. TWMTSLAACK goto i. Send the High 8 bit of I2. C Address. TWDR i. Transmit I2. C Data. I2. CDATA Check the TWSR status. TWMTDATAACK goto i. Send the Low 8 bit of I2. C Address. TWDR i. Transmit I2. C Data. I2. CDATA Check the TWSR status. TWMTDATAACK goto i. Put data into data register and start transmission. TWDR data Transmit I2. C Data. twistatusi. I2. CDATA Check the TWSR status. TWMTDATAACK goto i. TWI Transmit Ok. rval1 i. Transmit I2. C Data. I2. CSTOP. return rval. MAXTRIES return rval Transmit Start Condition. I2. CSTART. Check the TWSR status. TWMTARBLOST goto i. TWSTART twistatus TWREPSTART goto i. Send slave address SLAW 0xa. TWDR devid 0x. F0 devaddr lt lt 1 0x. E TWWRITE Transmit I2. C Data. twistatusi. I2. CDATA Check the TWSR status. TWMTSLANACK twistatus TWMTARBLOST goto i. TWMTSLAACK goto i. Send the High 8 bit of I2. C Address. TWDR i. Transmit I2. C Data. I2. CDATA Check the TWSR status. TWMTDATAACK goto i. Send the Low 8 bit of I2. C Address. TWDR i. Transmit I2. C Data. I2. CDATA Check the TWSR status. TWMTDATAACK goto i. Send start Condition. I2. CSTART Check the TWSR status. TWMTARBLOST goto i. TWSTART twistatus TWREPSTART goto i. Send slave address SLAR. TWDR devid 0x. F0 devaddr lt lt 1 0x. E TWREAD Transmit I2. C Data. twistatusi. I2. CDATA. Check the TWSR status. TWMRSLANACK twistatus TWMRARBLOST goto i. TWMRSLAACK goto i. Read I2. C Data. twistatusi. I2. CDATA. if twistatus TWMRDATANACK goto i. Get the Data. rval1 i. Send Stop Condition. I2. CSTOP. return rval. DDRD0x. FF Set PORTD as Output. PORTD0x. 00 Set All PORTD to Low Initial ADC Peripheral for Users Trimpot Input. ADMUX0x. 00 Select Channel 0 PC0 Initial the ADC Circuit. ADCSRA 1lt lt ADEN 1lt lt ADPS2 1lt lt ADPS1 Free running Mode. ADCSRB 0x. 00 Disable digital input on ADC0 PC0. DIDR0 0x. 01 Initial TWI Peripheral. TWSR 0x. 00 Select Prescaler of 1 SCL frequency 1. TWBR 0x. 30 4. Decimal. Read the EEPROM ID. Start at Address 0. EEPROMID,EEPROMADDR, id. EEPROMID,EEPROMADDR, id. Write to EEPROM if no ID defined. EEPROMID,EEPROMADDR,bufferi. Initial Delay Value. Start conversion by setting ADSC on ADCSRA Register. ADCSRA 1lt lt ADSC wait until convertion complete ADSC0 Complete. ADCSRA 1lt lt ADSC Get the ADC Result. ADCW Read the EEPROM. EEPROMID,EEPROMADDR, data Put data to the PORTD. PORTDdata delaymsidelay Delay. EOF i. 2cbus. c Inside the C Code. 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