avr-twi

Nonblocking TWI/I2C master driver for Atmel AVR

API

void twi_init()

Initializes the driver. Should be called once before calling any other TWI functions.

void twi_write(uint8_t address, uint8_t* data, uint8_t length, void (*callback)(uint8_t address, uint8_t *data))

Writes data to the given address.

• address - TWI slave address
• data - pointer to data buffer
• length - numer of bytes to write from the given data buffer
• callback - function pointer to callback (called when write completes)

The callback should accept two arguments:

• address - TWI slave address
• data - pointer to data buffer that was written

void twi_read(uint8_t address, uint8_t length, void (*callback)(uint8_t address, uint8_t *data))

Reads data from the given address.

• address - TWI slave address
• length - number of bytes to read
• callback - function pointer to callback (called when read is complete)

The callback should accept two arguments:

• address - TWI slave address
• data - pointer to data buffer that was written

uint8_t *twi_wait()

This will block until the current operation (read or write) completes or return immediately if there is no operation in progress. It returns a pointer to the internal TWI buffer. This is useful for performing initialization read/writes where asynchrony may be unnecessary. Call it between read/write calls.

twi_write(address, &data, 2, NULL);
twi_wait();
twi_read(address, 2, NULL);
uint8_t *result = twi_wait();

Definitions

• F_CPU - you should define this before including this library
• TWI_FREQ - defaults to 100kHz if left undefined
• TWI_BUFFER_LENGTH - defaults to 32 if left undefined