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This driver is the implementation of TWI module of megaRF device as master.

Master initiates and terminates a data transmission. The transmission is initiated when the Master issues a START condition on the bus, and it is terminated when the Master issues a STOP condition. This uses two bi-directional bus lines(PD0 and PD1) one for clock (SCL) and one for data (SDA)

Configuration

Configuration is done in the configuration file : conf_twi.h

Configuration defines:

SLAVE_BUS_ADDR : TWI slave bus address
SLAVE_MEM_ADDR_LENGTH : TWI slave memory address length
TWI_SPEED_HZ : TWI data transfer rate

Interface

The twi module should be configured as master. The SCL period is controlled by settings in the TWI Bit Rate Register (TWBR) and the Prescaler bits in the TWI Status Register (TWSR). Enabling of TWI clock source and interrupt is done by calling the function

twi_master_setup()

Usage

The include file is needed:

#include "twi_megarf.h"

TWI transmission is to transmit a START condition. This is done by writing a specific value into TWCR, instructing the TWI hardware to transmit START condition and then transmit the data. Similarly in receive mode This is done by calling:

twi_master_write() and twi_master_read()

After initiating the transmission or reception the completion status will be indicated to the application code through the following function

twi_master_get_status() and twi_master_read()

Functions
static void	twi_master_addr_ack (void)
	Notification that address byte was written to the TWI and need to send ACK or NACK. More...

static void	twi_master_bus_reset (void)
	Reset TWI bus. More...

static void	twi_master_data_write (void)
	Sending data to twi bus. More...

status_code_t	twi_master_get_status (void)
	returns the status of TWI bus More...

status_code_t	twi_master_init (volatile void twi, twi_master_options_t opt)
	Inits TWI module as master. More...

static void	twi_master_internal_addr_write (void)
	Sending internal device address to twi bus. More...

status_code_t	twi_master_read (volatile void twi, const twi_package_t package)
	Reads the series of bytes from the TWI bus. More...

static void	twi_master_read_done (uint8_t data)
	Notification that byte was read by the TWI. More...

static void	twi_master_read_last_byte (uint8_t data)
	Notification that last byte was read from the TWI. More...

static void	twi_master_start (void)
	Notification about the start condition was sent. More...

status_code_t	twi_master_write (volatile void twi, const twi_package_t package)
	Perform a TWI master write transfer. More...

static void	twi_master_write_done (void)
	Notification that byte was written to the TWI. More...

static void twi_master_addr_ack ( void )

static

Notification that address byte was written to the TWI and need to send ACK or NACK.

Parameters

none.

References ERR_PROTOCOL, master_transfer, twi_master_bus_reset(), TWI_READ_DATA, and twi_send_ack().

Referenced by twi_interrupt_handler().

static void twi_master_bus_reset ( void )

static

Reset TWI bus.

Parameters

none.

References master_transfer, TWI_IDLE, twi_master_busy, and twi_reset().

Referenced by twi_interrupt_handler(), twi_master_addr_ack(), twi_master_read_done(), twi_master_read_last_byte(), twi_master_start(), and twi_master_write_done().

static void twi_master_data_write ( void )

static

Sending data to twi bus.

If last byte then send stop condition.

Parameters

none.

References master_transfer, STATUS_OK, TWI_IDLE, twi_master_busy, twi_send_stop(), and twi_write_byte().

Referenced by twi_master_write_done().

status_code_t twi_master_get_status ( void )

returns the status of TWI bus

Parameters

none

References master_transfer.

Referenced by twi_master_read(), and twi_master_write().

status_code_t twi_master_init	(	volatile void *	twi,
		twi_master_options_t *	opt
	)

Inits TWI module as master.

This function is a TWI Master initialisation.

Parameters

opt	twi setting options (see twi_master_options_t)

References twi_master_options_t::baud_reg, cpu_irq_disable, cpu_irq_enable, MASTER, STATUS_OK, twi_interrupt_enable(), twi_mode, and TWI_PRESCALE_REG.

static void twi_master_internal_addr_write ( void )

static

Sending internal device address to twi bus.

Parameters

none.

References data, master_transfer, TWI_READ_DATA, twi_write_byte(), TWI_WRITE_DATA, and TWI_WRITE_IADDR_WRITE_DATA.

Referenced by twi_master_write_done().

status_code_t twi_master_read	(	volatile void *	twi,
		const twi_package_t *	package
	)

Reads the series of bytes from the TWI bus.

Parameters

package - Package information and data (see twi_package_t)

References ERR_INVALID_ARG, twi_package_t::length, master_transfer, NULL, OPERATION_IN_PROGRESS, twi_master_busy, twi_master_get_status(), TWI_READ_DATA, twi_send_start(), TWI_SLAVE_NO_INTERNAL_ADDRESS, and TWI_WRITE_IADDR_READ_DATA.

Referenced by main(), and run_twi_master_recv_test().

static void twi_master_read_done ( uint8_t data )

static

Notification that byte was read by the TWI.

Parameters

data	- contains byte that was read.

References data, ERR_PROTOCOL, master_transfer, twi_master_bus_reset(), TWI_READ_DATA, and twi_send_ack().

Referenced by twi_interrupt_handler().

static void twi_master_read_last_byte ( uint8_t data )

static

Notification that last byte was read from the TWI.

Needs to send STOP condition

Parameters

data	- contains byte that was read.

References data, ERR_PROTOCOL, master_transfer, STATUS_OK, TWI_IDLE, twi_master_bus_reset(), twi_master_busy, TWI_READ_DATA, and twi_send_stop().

Referenced by twi_interrupt_handler().

static void twi_master_start ( void )

static

Notification about the start condition was sent.

This function is a TWI Master start indication.

Parameters

none

References ERR_PROTOCOL, master_transfer, twi_master_bus_reset(), TWI_READ_DATA, TWI_READ_ENABLE, twi_write_byte(), TWI_WRITE_DATA, TWI_WRITE_ENABLE, TWI_WRITE_IADDR_READ_DATA, and TWI_WRITE_IADDR_WRITE_DATA.

Referenced by twi_interrupt_handler().

status_code_t twi_master_write	(	volatile void *	twi,
		const twi_package_t *	package
	)

Perform a TWI master write transfer.

This function is a TWI Master write transaction.

Parameters

package - Package information and data (see twi_package_t)

References ERR_INVALID_ARG, master_transfer, NULL, OPERATION_IN_PROGRESS, twi_master_busy, twi_master_get_status(), twi_send_start(), TWI_SLAVE_NO_INTERNAL_ADDRESS, TWI_WRITE_DATA, and TWI_WRITE_IADDR_WRITE_DATA.

Referenced by main(), and run_twi_master_send_test().

static void twi_master_write_done ( void )

static

Notification that byte was written to the TWI.

Parameters

result - contains result of previous operation.

References ERR_PROTOCOL, master_transfer, twi_master_bus_reset(), twi_master_data_write(), twi_master_internal_addr_write(), TWI_READ_DATA, twi_send_start(), TWI_WRITE_DATA, TWI_WRITE_IADDR_READ_DATA, and TWI_WRITE_IADDR_WRITE_DATA.

Referenced by twi_interrupt_handler().