Elisa3
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I2C (TWI) Master Software Library. More...
I2C (TWI) Master Software Library.
Basic routines for communicating with I2C slave devices. This single master implementation is limited to one bus master on the I2C bus.
This I2c library is implemented as a compact assembler software implementation of the I2C protocol which runs on any AVR (i2cmaster.S) and as a TWI hardware interface for all AVR with built-in TWI hardware (twimaster.c). Since the API for these two implementations is exactly the same, an application can be linked either against the software I2C implementation or the hardware I2C implementation.
Use 4.7k pull-up resistor on the SDA and SCL pin.
Adapt the SCL and SDA port and pin definitions and eventually the delay routine in the module i2cmaster.S to your target when using the software I2C implementation !
Adjust the CPU clock frequence F_CPU in twimaster.c or in the Makfile when using the TWI hardware implementaion.
#include <i2cmaster.h> #define Dev24C02 0xA2 // device address of EEPROM 24C02, see datasheet int main(void) { unsigned char ret; i2c_init(); // initialize I2C library // write 0x75 to EEPROM address 5 (Byte Write) i2c_start_wait(Dev24C02+I2C_WRITE); // set device address and write mode i2c_write(0x05); // write address = 5 i2c_write(0x75); // write value 0x75 to EEPROM i2c_stop(); // set stop conditon = release bus // read previously written value back from EEPROM address 5 i2c_start_wait(Dev24C02+I2C_WRITE); // set device address and write mode i2c_write(0x05); // write address = 5 i2c_rep_start(Dev24C02+I2C_READ); // set device address and read mode ret = i2c_readNak(); // read one byte from EEPROM i2c_stop(); for(;;); }