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/*****************************************************************************

*

* Atmel Corporation

*

* File              : TWI_Slave.c

* Compiler          : IAR EWAAVR 2.28a/3.10c

* Revision          : $Revision: 2475 $

* Date              : $Date: 2007-09-20 12:00:43 +0200 (to, 20 sep 2007) $

* Updated by        : $Author: mlarsson $

*

* Support mail      : avr@atmel.com

*

* Supported devices : All devices with a TWI module can be used.

*                     The example is written for the ATmega16

*

* AppNote           : AVR311 - TWI Slave Implementation

*

* Description       : This is sample driver to AVRs TWI module.

*                     It is interupt driveren. All functionality is controlled through

*                     passing information to and from functions. Se main.c for samples

*                     of how to use the driver.

*

****************************************************************************/

/*! \page MISRA

 *

 * General disabling of MISRA rules:

 * * (MISRA C rule 1) compiler is configured to allow extensions

 * * (MISRA C rule 111) bit fields shall only be defined to be of type unsigned int or signed int

 * * (MISRA C rule 37) bitwise operations shall not be performed on signed integer types

 * As it does not work well with 8bit architecture and/or IAR

 * Other disabled MISRA rules

 * * (MISRA C rule 109) use of union - overlapping storage shall not be used

 * * (MISRA C rule 61) every non-empty case clause in a switch statement shall be terminated with a break statement

*/

#if defined(__ICCAVR__)

#include "ioavr.h"              

#include "inavr.h"

#else

#include <avr/io.h>

#include <avr/interrupt.h>

#endif

#include "twi_slave.h"

// Emulate GCC ISR() statement in IAR

#if defined(__ICCAVR__)

#define PRAGMA(x) _Pragma( #x )

#define ISR(vec) PRAGMA( vector=vec ) __interrupt void handler_##vec(void)

#endif 

static unsigned char TWI_buf[TWI_BUFFER_SIZE];     // Transceiver buffer. Set the size in the header file

static unsigned char TWI_msgSize  = 0;             // Number of bytes to be transmitted.

static unsigned char TWI_state    = TWI_NO_STATE;  // State byte. Default set to TWI_NO_STATE.

// This is true when the TWI is in the middle of a transfer

// and set to false when all bytes have been transmitted/received

// Also used to determine how deep we can sleep.

static volatile unsigned char TWI_busy = 0;

union TWI_statusReg_t TWI_statusReg = {0};           // TWI_statusReg is defined in TWI_Slave.h

/****************************************************************************

Call this function to set up the TWI slave to its initial standby state.

Remember to enable interrupts from the main application after initializing the TWI.

Pass both the slave address and the requrements for triggering on a general call in the

same byte. Use e.g. this notation when calling this function:

TWI_Slave_Initialise( (TWI_slaveAddress<<TWI_ADR_BITS) | (TRUE<<TWI_GEN_BIT) );

The TWI module is configured to NACK on any requests. Use a TWI_Start_Transceiver function to

start the TWI.

****************************************************************************/

void twi_slave_init( unsigned char TWI_ownAddress )

{

  TWAR = TWI_ownAddress;                            // Set own TWI slave address. Accept TWI General Calls.

  TWCR = (1<<TWEN)|                                 // Enable TWI-interface and release TWI pins.

         (0<<TWIE)|(0<<TWINT)|                      // Disable TWI Interupt.

         (0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Do not ACK on any requests, yet.

         (0<<TWWC);                                 //

  TWI_busy = 0;

}    

/****************************************************************************

Call this function to test if the TWI_ISR is busy transmitting.

****************************************************************************/

unsigned char twi_slave_busy( void )

{

  return TWI_busy;

}

/****************************************************************************

Call this function to fetch the state information of the previous operation. The function will hold execution (loop)

until the TWI_ISR has completed with the previous operation. If there was an error, then the function

will return the TWI State code.

****************************************************************************/

unsigned char twi_slave_get_status( void )

{

  while ( twi_slave_busy() ) {}             // Wait until TWI has completed the transmission.

  return ( TWI_state );                         // Return error state. 

}

/****************************************************************************

Call this function to send a prepared message, or start the Transceiver for reception. Include

a pointer to the data to be sent if a SLA+W is received. The data will be copied to the TWI buffer.

Also include how many bytes that should be sent. Note that unlike the similar Master function, the

Address byte is not included in the message buffers.

The function will hold execution (loop) until the TWI_ISR has completed with the previous operation,

then initialize the next operation and return.

****************************************************************************/

void twi_slave_start_with_data( unsigned char *msg, unsigned char msgSize )

{

  unsigned char temp;

  while ( twi_slave_busy() ) {}             // Wait until TWI is ready for next transmission.

  TWI_msgSize = msgSize;                        // Number of data to transmit.

  for ( temp = 0; temp < msgSize; temp++ )      // Copy data that may be transmitted if the TWI Master requests data.

  {

    TWI_buf[ temp ] = msg[ temp ];

  }

  TWI_statusReg.all = 0;      

  TWI_state         = TWI_NO_STATE ;

  TWCR = (1<<TWEN)|                             // TWI Interface enabled.

         (1<<TWIE)|(1<<TWINT)|                  // Enable TWI Interupt and clear the flag.

         (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|       // Prepare to ACK next time the Slave is addressed.

         (0<<TWWC);                             //

  TWI_busy = 1;

}

/****************************************************************************

Call this function to start the Transceiver without specifing new transmission data. Useful for restarting

a transmission, or just starting the transceiver for reception. The driver will reuse the data previously put

in the transceiver buffers. The function will hold execution (loop) until the TWI_ISR has completed with the

previous operation, then initialize the next operation and return.

****************************************************************************/

void twi_slave_start( void )

{

  while ( twi_slave_busy() ) {}             // Wait until TWI is ready for next transmission.

  TWI_statusReg.all = 0;      

  TWI_state         = TWI_NO_STATE ;

  TWCR = (1<<TWEN)|                             // TWI Interface enabled.

         (1<<TWIE)|(1<<TWINT)|                  // Enable TWI Interupt and clear the flag.

         (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|       // Prepare to ACK next time the Slave is addressed.

         (0<<TWWC);                             //

  TWI_busy = 0;

}

/****************************************************************************

Call this function to read out the received data from the TWI transceiver buffer. I.e. first call

TWI_Start_Transceiver to get the TWI Transceiver to fetch data. Then Run this function to collect the

data when they have arrived. Include a pointer to where to place the data and the number of bytes

to fetch in the function call. The function will hold execution (loop) until the TWI_ISR has completed

with the previous operation, before reading out the data and returning.

If there was an error in the previous transmission the function will return the TWI State code.

****************************************************************************/

unsigned char twi_slave_get_data( unsigned char *msg, unsigned char msgSize )

{

  unsigned char i;

  while ( twi_slave_busy() ) {}             // Wait until TWI is ready for next transmission.

  if( TWI_statusReg.lastTransOK )               // Last transmission completed successfully.              

  {                                            

    for ( i=0; i<msgSize; i++ )                 // Copy data from Transceiver buffer.

    {

      msg[ i ] = TWI_buf[ i ];

    }

    TWI_statusReg.RxDataInBuf = FALSE;          // Slave Receive data has been read from buffer.

  }

  return( TWI_statusReg.lastTransOK );                                  

}

// ********** Interrupt Handlers ********** //

/****************************************************************************

This function is the Interrupt Service Routine (ISR), and called when the TWI interrupt is triggered;

that is whenever a TWI event has occurred. This function should not be called directly from the main

application.

****************************************************************************/

ISR(TWI_vect)

{

  static unsigned char TWI_bufPtr;

  switch (TWSR)

  {

    case TWI_STX_ADR_ACK:            // Own SLA+R has been received; ACK has been returned

//    case TWI_STX_ADR_ACK_M_ARB_LOST: // Arbitration lost in SLA+R/W as Master; own SLA+R has been received; ACK has been returned

      TWI_bufPtr   = 0;                                 // Set buffer pointer to first data location

    case TWI_STX_DATA_ACK:           // Data byte in TWDR has been transmitted; ACK has been received

      TWDR = TWI_buf[TWI_bufPtr++];

      TWCR = (1<<TWEN)|                                 // TWI Interface enabled

             (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to send byte

             (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // 

             (0<<TWWC);                                 //

      TWI_busy = 1;

      break;

    case TWI_STX_DATA_NACK:          // Data byte in TWDR has been transmitted; NACK has been received. 

                                     // I.e. this could be the end of the transmission.

      if (TWI_bufPtr == TWI_msgSize) // Have we transceived all expected data?

      {

        TWI_statusReg.lastTransOK = TRUE;               // Set status bits to completed successfully. 

      }

      else                          // Master has sent a NACK before all data where sent.

      {

        TWI_state = TWSR;                               // Store TWI State as errormessage.      

      }        

      TWCR = (1<<TWEN)|                                 // Enable TWI-interface and release TWI pins

             (1<<TWIE)|(1<<TWINT)|                      // Keep interrupt enabled and clear the flag

             (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Answer on next address match

             (0<<TWWC);                                 //

      TWI_busy = 0;   // Transmit is finished, we are not busy anymore

      break;    

    case TWI_SRX_GEN_ACK:            // General call address has been received; ACK has been returned

//    case TWI_SRX_GEN_ACK_M_ARB_LOST: // Arbitration lost in SLA+R/W as Master; General call address has been received; ACK has been returned

      TWI_statusReg.genAddressCall = TRUE;

    case TWI_SRX_ADR_ACK:            // Own SLA+W has been received ACK has been returned

//    case TWI_SRX_ADR_ACK_M_ARB_LOST: // Arbitration lost in SLA+R/W as Master; own SLA+W has been received; ACK has been returned    

                                                        // Dont need to clear TWI_S_statusRegister.generalAddressCall due to that it is the default state.

      TWI_statusReg.RxDataInBuf = TRUE;      

      TWI_bufPtr   = 0;                                 // Set buffer pointer to first data location

                                                        // Reset the TWI Interupt to wait for a new event.

      TWCR = (1<<TWEN)|                                 // TWI Interface enabled

             (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to send byte

             (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Expect ACK on this transmission

             (0<<TWWC);  

      TWI_busy = 1;

      break;

    case TWI_SRX_ADR_DATA_ACK:       // Previously addressed with own SLA+W; data has been received; ACK has been returned

    case TWI_SRX_GEN_DATA_ACK:       // Previously addressed with general call; data has been received; ACK has been returned

      // TODO: What is this? Seems to be no bounds checking!

      TWI_buf[TWI_bufPtr++]     = TWDR;

      TWI_statusReg.lastTransOK = TRUE;                 // Set flag transmission successfull.       

                                                        // Reset the TWI Interupt to wait for a new event.

      TWCR = (1<<TWEN)|                                 // TWI Interface enabled

             (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to send byte

             (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Send ACK after next reception

             (0<<TWWC);                                 // 

      TWI_busy = 1;

      break;

    case TWI_SRX_STOP_RESTART:       // A STOP condition or repeated START condition has been received while still addressed as Slave    

                                                        // Enter not addressed mode and listen to address match

      TWCR = (1<<TWEN)|                                 // Enable TWI-interface and release TWI pins

             (1<<TWIE)|(1<<TWINT)|                      // Enable interrupt and clear the flag

             (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Wait for new address match

             (0<<TWWC);                                 //

      TWI_busy = 0;  // We are waiting for a new address match, so we are not busy

      break;          

    case TWI_SRX_ADR_DATA_NACK:      // Previously addressed with own SLA+W; data has been received; NOT ACK has been returned

    case TWI_SRX_GEN_DATA_NACK:      // Previously addressed with general call; data has been received; NOT ACK has been returned

    case TWI_STX_DATA_ACK_LAST_BYTE: // Last data byte in TWDR has been transmitted (TWEA = �0�); ACK has been received

//    case TWI_NO_STATE              // No relevant state information available; TWINT = �0�

    case TWI_BUS_ERROR:         // Bus error due to an illegal START or STOP condition

      TWI_state = TWSR;                 //Store TWI State as errormessage, operation also clears noErrors bit

      TWCR =   (1<<TWSTO)|(1<<TWINT);   //Recover from TWI_BUS_ERROR, this will release the SDA and SCL pins thus enabling other devices to use the bus

      break;

    default:    

      TWI_state = TWSR;                                 // Store TWI State as errormessage, operation also clears the Success bit.      

      TWCR = (1<<TWEN)|                                 // Enable TWI-interface and release TWI pins

             (1<<TWIE)|(1<<TWINT)|                      // Keep interrupt enabled and clear the flag

             (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Acknowledge on any new requests.

             (0<<TWWC);                                 //

      TWI_busy = 0; // Unknown status, so we wait for a new address match that might be something we can handle

  }

}

/*

void example(){

        unsigned char messageBuf[TWI_BUFFER_SIZE];

  unsigned char TWI_slaveAddress;

  // LED feedback port - connect port B to the STK500 LEDS

  DDRB  = 0xFF; // Set to ouput

  PORTB = 0x55; // Startup pattern

  // Own TWI slave address

  TWI_slaveAddress = 0x10;

  // Initialise TWI module for slave operation. Include address and/or enable General Call.

  TWI_Slave_Initialise( (unsigned char)((TWI_slaveAddress<<TWI_ADR_BITS) | (TRUE<<TWI_GEN_BIT) ));

  SEI();

  // Start the TWI transceiver to enable reseption of the first command from the TWI Master.

  TWI_Start_Transceiver();

  // This example is made to work together with the AVR315 TWI Master application note. In adition to connecting the TWI

  // pins, also connect PORTB to the LEDS. The code reads a message as a TWI slave and acts according to if it is a

  // general call, or an address call. If it is an address call, then the first byte is considered a command byte and

  // it then responds differently according to the commands.

  // This loop runs forever. If the TWI is busy the execution will just continue doing other operations.

  for(;;)

  {

    #ifdef POWER_MANAGEMENT_ENABLED

      // Sleep while waiting for TWI transceiver to complete or waiting for new commands.

      // If we have data in the buffer, we can't enter sleep because we have to take care

      // of it first.

      // If the transceiver is busy, we enter idle mode because it will wake up by all TWI

      // interrupts.

      // If the transceiver not is busy, we can enter power-down mode because next receive

      // should be a TWI address match and it wakes the device up from all sleep modes.

      if( ! TWI_statusReg.RxDataInBuf ) {

        if(TWI_Transceiver_Busy()) {

          MCUCR = (1<<SE)|(0<<SM2)|(0<<SM1)|(0<<SM0); // Enable sleep with idle mode

        } else {

          MCUCR = (1<<SE)|(0<<SM2)|(1<<SM1)|(0<<SM0); // Enable sleep with power-down mode

        }

        SLEEP();

      } else {

        NOP(); // There is data in the buffer, code below takes care of it.

      }

    #else // No power management

      // Here you can add your own code that should be run while waiting for the TWI to finish    

      NOP(); // Put own code here.

    #endif

    // Check if the TWI Transceiver has completed an operation.

    if ( ! TWI_Transceiver_Busy() )                              

    {

      // Check if the last operation was successful

      if ( TWI_statusReg.lastTransOK )

      {

        // Check if the last operation was a reception

        if ( TWI_statusReg.RxDataInBuf )

        {

          TWI_Get_Data_From_Transceiver(messageBuf, 2);        

          // Check if the last operation was a reception as General Call        

          if ( TWI_statusReg.genAddressCall )

          {

            // Put data received out to PORTB as an example.        

            PORTB = messageBuf[0];

          }              

          else // Ends up here if the last operation was a reception as Slave Address Match  

          {

            // Example of how to interpret a command and respond.

            // TWI_CMD_MASTER_WRITE stores the data to PORTB

            if (messageBuf[0] == TWI_CMD_MASTER_WRITE)

            {

              PORTB = messageBuf[1];                            

            }

            // TWI_CMD_MASTER_READ prepares the data from PINB in the transceiver buffer for the TWI master to fetch.

            if (messageBuf[0] == TWI_CMD_MASTER_READ)

            {

              messageBuf[0] = PINB;

              TWI_Start_Transceiver_With_Data( messageBuf, 1 );

            }

          }

        }                

        else // Ends up here if the last operation was a transmission  

        {

            NOP(); // Put own code here.

        }

        // Check if the TWI Transceiver has already been started.

        // If not then restart it to prepare it for new receptions.            

        if ( ! TWI_Transceiver_Busy() )

        {

          TWI_Start_Transceiver();

        }

      }

      else // Ends up here if the last operation completed unsuccessfully

      {

        TWI_Act_On_Failure_In_Last_Transmission( TWI_Get_State_Info() );

      }

    }

  }

}*/