twi slave Driver

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

Master initiates and terminates a data transmission.In the Slave Transmitter mode, a number of data bytes are transmitted to a Master. In the Slave Receiver mode, a number of data bytes are received from a Master. This uses two bi-directional bus lines(PD0 and PD1), one to receive clock (SCL) from master 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 to respond to master
• TWI_GCE : TWI slave general call enable. TWI will respond to the general call address (0x00), otherwise it will ignore the general call address

Interface

The twi module should be configured as slave. The slave address is set in TWAR register. The upper 7 bits are the address to which the 2-wire Serial Interface will respond when addressed by a Master. If the LSB is set(TWI_GCE), the TWI will respond to the general call address (0x00), otherwise it will ignore the general call address. Enabling of TWI as slave is done by calling the function:

twi_slave_start() 

Usage

The include file needed is:

#include "twi_megarf.h" 

After initiating the twi as slave,the TWI waits until it is addressed by its own slave address (or the general call address if enabled) followed by the data direction bit. If the direction bit is (read), the TWI will operate in Slave transmit mode, otherwise Slave receive mode is entered

The status and state is indicated to the application code through the following functions

twi_slave_status_get() and twi_slave_state_get() 

Functions
static void	twi_slave_bus_reset (void)
	Reset TWI bus. More...
static void	twi_slave_data_read (uint8_t data)
	Read received data. More...
static void	twi_slave_data_write (void)
	Sending data to twi bus. More...
static void	twi_slave_enable (void)
	Enable TWI as slave. More...
status_code_t	twi_slave_init (uint8_t twi_slave_ownadd)
	Initialize TWI as Slave. More...
static void	twi_slave_last_byte_write_done (void)
	Notification of Last byte is transmitted. More...
status_code_t	twi_slave_start (slave_data_buffer_t *package)
	Start the slave Transceiver. More...
int	twi_slave_state_get (void)
	Get the state of TWI transceiver. More...
int	twi_slave_status_get (void)
	Get the status of TWI transceiver. More...
void	twi_slave_status_reset (void)
	Resets the slave state and status to initial for next transmission/reception. More...
static void	twi_slave_write_byte (uint8_t data)
	writing an byte to TWI. More...

static void twi_slave_bus_reset ( void  )

static

Reset TWI bus.

Parameters

none.

References slave_transfer, TWI_IDLE, and twi_reset().

Referenced by twi_interrupt_handler().

static void twi_slave_data_read ( uint8_t  data )

static

Read received data.

Parameters

data	- Contains data read from twi bus to be written to data receive buffer.

References data, slave_transfer, and twi_slave_enable().

Referenced by twi_interrupt_handler().

static void twi_slave_data_write ( void  )

static

Sending data to twi bus.

Parameters

none.

References slave_transfer, and twi_slave_write_byte().

Referenced by twi_interrupt_handler().

static void twi_slave_enable ( void  )

inlinestatic

Enable TWI as slave.

Parameters

none.

Referenced by twi_interrupt_handler(), twi_slave_data_read(), twi_slave_last_byte_write_done(), twi_slave_status_reset(), and twi_slave_write_byte().

status_code_t twi_slave_init

(

uint8_t

twi_slave_ownadd

)

Initialize TWI as Slave.

Parameters

TWI_ownAddress

- contains Slave own Address

References slave_transfer, STATUS_OK, TWI_IDLE, and TWI_STATUS_NO_STATE.

Referenced by main(), and twi_slave_setup().

static void twi_slave_last_byte_write_done ( void  )

static

Notification of Last byte is transmitted.

Parameters

none.

References slave_transfer, TWI_IDLE, twi_slave_enable(), and TWI_STATUS_TX_COMPLETE.

Referenced by twi_interrupt_handler().

status_code_t twi_slave_start

(

slave_data_buffer_t *

package

)

Start the slave Transceiver.

Returns

status_code_t - status of twi slave

References OPERATION_IN_PROGRESS, slave_transfer, STATUS_OK, TWI_IDLE, and twi_slave_status_reset().

Referenced by main().

int twi_slave_state_get

(

void

)

Get the state of TWI transceiver.

Returns

int - state information

References slave_transfer.

Referenced by main().

int twi_slave_status_get

(

void

)

Get the status of TWI transceiver.

Get the Status of TWI transceiver.

Returns

int - status information

References slave_transfer.

Referenced by main().

void twi_slave_status_reset

(

void

)

Resets the slave state and status to initial for next transmission/reception.

References SLAVE, slave_transfer, TWI_IDLE, twi_mode, twi_slave_enable(), and TWI_STATUS_NO_STATE.

Referenced by twi_Receive_Success(), twi_slave_start(), twi_Transmission_Failure(), and twi_Transmit_Success().

static void twi_slave_write_byte ( uint8_t  data )

inlinestatic

writing an byte to TWI.

Parameters

data	- contains the data to transmitted ro master.

References data, and twi_slave_enable().

Referenced by twi_slave_data_write().