usart.c

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#include "usart.h"

/*
 * Description: Check if the usart is in multidrop
 * Arguments:   *usart: Base address of the usart
 * Returns:     1 if the usart is in multidrop mode, otherwise 0
 */

static int usart_mode_is_multidrop(volatile struct avr32_usart_t * usart)
{
  return ( (usart->mr & 0x00000600) >> AVR32_USART_MR_PAR_OFFSET );
}

void usart_reset( volatile struct avr32_usart_t * usart)
{
        /* Disable all usart interrupts, interrupts needed should be set
           explicitly on every reset */
        usart->idr = 0xFFFFffff;

        /* Reset mode and other registers that could cause unpredictable
           behaviour after reset */
        usart->mr = 0;
        usart->rtor = 0;
        usart->ttgr = 0;

        /* Shutdown RX and TX (will be reenabled when setup
           is completed successfully), reset status bits and turn
           off DTR and RTS */
        usart->cr = (1 << AVR32_USART_CR_RSTRX_OFFSET) |
                    (1 << AVR32_USART_CR_RSTTX_OFFSET) |
                    (1 << AVR32_USART_CR_RSTSTA_OFFSET) |
                    (1 << AVR32_USART_CR_RSTIT_OFFSET) |
                    (1 << AVR32_USART_CR_RSTNACK_OFFSET) |
                    (1 << AVR32_USART_CR_DTRDIS_OFFSET) |
                    (1 << AVR32_USART_CR_RTSDIS_OFFSET);
}


static int usart_set_baudrate( volatile struct avr32_usart_t * usart, unsigned int baudrate, long cpu_hz)
{
        int cd; /* Clock divider */

        /*
         *             ** BAUDRATE CALCULATION **
         *
         *                 Selected Clock                       Selected Clock
         *     baudrate = ----------------   or     baudrate = ----------------
         *                             16 x CD                                        8 x CD
         *
         *       (with 16x oversampling)              (with 8x oversampling)
         */

        if ( baudrate < (cpu_hz/16)  ){
                /* Use 8x oversampling */
                usart->mr |= (1<<AVR32_USART_MR_OVER_OFFSET);
                cd = cpu_hz / (8*baudrate);

                if (cd < 2) {
                        return USART_INVALID_INPUT;
                }
                usart->brgr = (cd << AVR32_USART_BRGR_CD_OFFSET);
        } else {
                /* Use 16x oversampling */
                usart->mr &= ~(1<<AVR32_USART_MR_OVER_OFFSET);
                cd =  cpu_hz / (16*baudrate);

                if (cd > 65535) {
                  /* Baudrate is too low */
                  return USART_INVALID_INPUT;
                }
        }
        usart->brgr = (cd << AVR32_USART_BRGR_CD_OFFSET);
        return USART_SUCCESS;
}




 /*---------------------------------------------------------------------------+
 |                                                                            |
 |                           INITIALIZATION FUNCTIONS                         |
 |                                                                            |
 +---------------------------------------------------------------------------*/


int usart_init_rs232(volatile struct avr32_usart_t * usart, struct usart_options_t * opt, long cpu_hz)
{
        int retval;

        /* Reset the usart and shutdown RX and TX */
        usart_reset(usart);

        /* Control input values */
        if (opt == 0) /* Null pointer */
                return USART_INVALID_INPUT;
        if (opt->charlength < 5 || opt->charlength > 9)
                return USART_INVALID_INPUT;
        if (opt->paritytype > 7)
                return USART_INVALID_INPUT;
        if (opt->stopbits > 2+255)
                return USART_INVALID_INPUT;
        if (opt->channelmode > 3)
                return USART_INVALID_INPUT;

        if ((retval = usart_set_baudrate(usart, opt->baudrate, cpu_hz)) != \
             USART_SUCCESS)
                return retval;

        if (opt->charlength == 9) {
                /* Charlength set to 9 bits; MODE9 dominates CHRL */
                usart->mr |= (1<<AVR32_USART_MR_MODE9_OFFSET);
        } else {
                /* CHRL gives the charlength( - 5) when USART_MODE9=0 */
                usart->mr |=
                        ((opt->charlength-5) << AVR32_USART_MR_CHRL_OFFSET);
        }

        usart->mr |= (opt->channelmode << AVR32_USART_MR_CHMODE_OFFSET) |
                     (opt->paritytype << AVR32_USART_MR_PAR_OFFSET);

        if (opt->stopbits > 2)
        {
                /* Set two stop bits */
                usart->mr |= (2 << AVR32_USART_MR_NBSTOP_OFFSET);
                /* And a timeguard period gives the rest */
                usart->ttgr = (opt->stopbits-2);
        }
        else
                /* Insert 1, 1.5 or 2 stop bits */
                usart->mr |= (opt->stopbits << AVR32_USART_MR_NBSTOP_OFFSET);

        /* Setup complete; enable communication */
        /* Enable input and output */
        usart->cr |= (1<<AVR32_USART_CR_TXEN_OFFSET) |
                     (1<<AVR32_USART_CR_RXEN_OFFSET);

        return USART_SUCCESS;
}

/*
 * Description: This function is meant to be run after rs232_init().
 *              It sets up the usart to use handshaking in its communication.
 * Arguments:   *usart:    Base address of the usart
 *              *opt:      Options needed to set up RS232 communcation (see usart_options_t)
 *                              cpu_hz:    The clock frequency of the usart module
 *              software_handshaking:
 *                         1= Use software handshaking
 *                         0= Use hardware handshaking (requires extra wiring)
 *              xon_char:  Character sent from receiver to transmitter when more
 *                         data can be sent. (Software handshaking only)
 *              xoff_char: Sent from recv. to trans. when recv. buffers are full (sw)
 * Returns:     USART_SUCCESS or USART_INVALID_INPUT
 */
int usart_init_handshaking(volatile struct avr32_usart_t * usart, struct usart_options_t * opt,
                           long cpu_hz, int software_handshaking,
                           char xon_char, char xoff_char)
{
        int retval;

        /* First: Setup standard RS323 */
        if ((retval = usart_init_rs232(usart, opt, cpu_hz)) != USART_SUCCESS)
                return retval;

        if (software_handshaking == 0)
        {
                /* Clear previous mode */
                usart-> mr &= ~(0xf << AVR32_USART_MR_MODE_OFFSET);
                /* Hardware handshaking */
                usart-> mr |= (USART_MODE_HW_HSH << AVR32_USART_MR_MODE_OFFSET);
        }
        else if (software_handshaking == 1)
        {
                /* Clear previous mode */
                usart-> mr &= ~(0xf << AVR32_USART_MR_MODE_OFFSET);
                /* Software handshaking */
                usart-> mr |= (USART_MODE_SW_HSH << AVR32_USART_MR_MODE_OFFSET);
                /* Set XON and XOFF characters */
                usart->xxr = (xon_char << AVR32_USART_XXR_XON_OFFSET) |
                             (xoff_char << AVR32_USART_XXR_XOFF_OFFSET);
        }
        else
                return USART_INVALID_INPUT;

        return USART_SUCCESS;
}

/*
 * Description: Setup the usart to use the IrDA protocol
 * Arguments:   *usart:      Base address of the usart
 *              *opt:        Options needed to set up RS232 communcation (see usart_options_t)
 *                              cpu_hz:          The module's clock frequency
 *              irda_filter: Counter used to seperate received ones from zeros
 * Returns:     USART_SUCCESS or USART_INVALID_INPUT
 */
int usart_init_IrDA(volatile struct avr32_usart_t * usart, struct usart_options_t * opt,
                    long cpu_hz, unsigned char irda_filter)
{
        int retval;

        /* First: Setup standard RS323 */
        if ((retval = usart_init_rs232(usart, opt, cpu_hz)) != USART_SUCCESS)
                return retval;

        /* Set IrDA counter */
        usart->ifr = irda_filter;

        /* Activate "low-pass filtering" of input */
        usart->mr |= (1 << AVR32_USART_MR_FILTER_OFFSET);
        return USART_SUCCESS;
}

/*
 * Description: Setup the usart to use the Modem protocol, activating special inputs/outputs
 * Arguments:   *usart: Base address of the usart
 *              *opt:   Options needed to set up RS232 communcation (see usart_options_t)
*                               cpu_hz:          The module's clock frequency
 * Returns:     USART_SUCCESS or USART_INVALID_INPUT
 */
int usart_init_modem(volatile struct avr32_usart_t * usart, struct usart_options_t * opt, long cpu_hz)
{
        int retval;

        /* First: Setup standard RS323 */
        if ((retval = usart_init_rs232(usart, opt, cpu_hz)) != USART_SUCCESS)
                return retval;

        /* Clear previous mode */
        usart-> mr &= ~(0xf << AVR32_USART_MR_MODE_OFFSET);
        /* Set Modem mode */
        usart-> mr |= (USART_MODE_MODEM << AVR32_USART_MR_MODE_OFFSET);
        return USART_SUCCESS;
}


/*
 * Description: Setup the usart to use the RS485 protocol
 * Arguments:   *usart: Base address of the usart
 *              *opt:   Options needed to set up RS232 communcation (see usart_options_t)
 *                              cpu_hz: The module's clock frequency
 * Returns:     USART_SUCCESS: mode successfully initialized
 *              USART_INVALID_INPUT: one of the arguments are out of valid range
 *              USART_MODE_FAULT: mode not initialized with multidrop parity
 */
int usart_init_rs485(volatile struct avr32_usart_t * usart, struct usart_options_t * opt, long cpu_hz)
{
        int retval;

        /* First: Setup standard RS323 */
        if ((retval = usart_init_rs232(usart, opt, cpu_hz)) != USART_SUCCESS)
                return retval;

        /* Clear previous mode */
        usart->mr &= ~(0xf << AVR32_USART_MR_MODE_OFFSET);
        /* Set Modem mode */
        usart->mr |= (USART_MODE_RS485 << AVR32_USART_MR_MODE_OFFSET);
        return USART_SUCCESS;
}


/*
 * Description: Setup the usart to use ISO7816 T=0 or T=1 smartcard protocol
 * Arguments:   *usart: Base address of the usart
 *              *opt:   Options needed to set up ISO7816 (see iso7816_options_t)
 *              t:      Which ISO7816 mode to use (T=0 or T=1)
 * Returns:     USART_SUCCESS or USART_INVALID_INPUT
 */
int usart_init_iso7816(volatile struct avr32_usart_t * usart, const struct iso7816_options_t * opt, int t, const long cpu_hz)
{
        int retval;

        /* Reset the usart and shutdown RX and TX */
        usart_reset(usart);

        if (opt == 0)
                /* Null pointer */
                return USART_INVALID_INPUT;

        /* Don't care about charlength, parity or channelmode; All these fields
           are ignored in iso7816 mode. 8bit characters and even parity is always
           used */

        if (t == 0)
        {
                /* Set USART mode to ISO7816, T=0 */
                /* The T=0 protocol always use 2 stop bits */
                usart->mr = (USART_MODE_ISO7816_T0 << AVR32_USART_MR_MODE_OFFSET) |
                            (2 << AVR32_USART_MR_NBSTOP_OFFSET) |
                            (opt->bit_order << AVR32_USART_MR_MSBF_OFFSET); /* Allow MSBF in T=0 */
        }
        else if (t == 1)
        {
                /* Only LSB first in the T=1 protocol */
                if (opt->bit_order != 0)
                        return USART_INVALID_INPUT;
                /* max_iterations field is only used in T=0 mode */
                if (opt->max_iterations != 0)
                        return USART_INVALID_INPUT;
                /* Set USART mode to ISO7816, T=1 */
                usart->mr = (USART_MODE_ISO7816_T1 << AVR32_USART_MR_MODE_OFFSET);
                /* The T=1 protocol always use 1 stop bit (no change needed) */
        }
        else
                return USART_INVALID_INPUT;

        if ((retval = usart_set_baudrate(usart, opt->iso7816_hz, cpu_hz)) != USART_SUCCESS)
                return retval;

        /* Set FIDI register: bit rate = selected clock/FI_DI_ratio/16 */
        usart->fidi = opt->fidi_ratio;
        /* Set ISO7816 spesific options in the MODE register */
        usart->mr |= (opt->inhibit_nack << AVR32_USART_MR_INACK_OFFSET) |
                     (opt->dis_suc_nack << AVR32_USART_MR_DSNACK_OFFSET) |
                     (opt->max_iterations << AVR32_USART_MR_MAX_ITERATION_OFFSET) |
                     (1 << AVR32_USART_MR_CLKO_OFFSET); /* Enable clock output */

        /* Setup complete; enable input */
        /* Leave TX disabled for now */
        usart->cr |= (1<<AVR32_USART_CR_RXEN_OFFSET);

        return USART_SUCCESS;
}




 /*---------------------------------------------------------------------------+
 |                                                                            |
 |                     READ AND RESET ERROR STATUS BITS                       |
 |                                                                            |
 +---------------------------------------------------------------------------*/

/*
 * Description: This function resets the status bits indicating that a parity error,
 *              framing error or overrun has occured. The rxbreak bit, indicating
 *              a start/end of break condition on the rx-line, is also reset.
 * Arguments:   *usart:  Base address of the usart
 * Returns:     nothing
 */
void usart_reset_status(volatile struct avr32_usart_t * usart)
{
        usart->cr |= (1<<AVR32_USART_CR_RSTSTA_OFFSET);
}

/*
 * Description: Checks if a parity error has occured since last status reset
 * Arguments:   *usart:  Base address of the usart
 * Returns:     1 if a parity error has been detected, otherwise 0
 */
int usart_parity_error(volatile struct avr32_usart_t * usart)
{
        return ((usart->csr & (1<<AVR32_USART_CSR_PARE_OFFSET)) != 0);
}


/*
 * Description: Checks if a framing error has occured since last status reset
 * Arguments:   *usart:  Base address of the usart
 * Returns:     1 if a framing error has been detected, otherwise 0
 */
int usart_framing_error(volatile struct avr32_usart_t * usart)
{
        return ((usart->csr & (1<<AVR32_USART_CSR_FRAME_OFFSET)) != 0);
}


/*
 * Description: Checks if a overrun error has occured since last status reset
 * Arguments:   *usart:  Base address of the usart
 * Returns:     1 if a overrun error has been detected, otherwise 0
 */
int usart_overrun_error(volatile struct avr32_usart_t * usart)
{
        return ((usart->csr & AVR32_USART_CSR_OVRE_OFFSET)) != 0;
}



 /*---------------------------------------------------------------------------+
 |                                                                            |
 |                         TRANSMIT/RECEIVE FUNCTIONS                         |
 |                                                                            |
 +---------------------------------------------------------------------------*/

/*
 * Description: While in RS485-mode, receviers only accept data addressed to them.
 *              A packet/char with the address tag set has to preceed any data.
 *              usart_send_address() is used to address a receiver. This receiver should read
 *              all the following data, until an address packet addresses someone else.
 * Arguments:   *usart:  Base address of the usart
 *              addr: the address of the target device
 * Returns:     USART_SUCCESS if the current mode is RS485
 *              USART_MODE_FAULT if called while in wrong mode
 */

int usart_send_address(volatile struct avr32_usart_t * usart, int address)
{
        /* Check if usart is in multidrop / RS485 mode */
        if ( usart_mode_is_multidrop(usart) )
        {
                /* Prepare to send an address */
                usart->cr |= (1<<AVR32_USART_CR_SENDA_OFFSET);

                /* Write the address to TX */
                usart_bw_write_char(usart, address);
                return USART_SUCCESS;
        } else {
                return USART_MODE_FAULT;
        }
}

/*
 * Description: Wait until the transmitter it ready (potentially forever),
 *              then transmit the given character
 * Arguments:   *usart:  Base address of the usart
 *              c:       The character (up to 9 bits) to transmit
 * Returns:     nothing
 */
inline void usart_bw_write_char(volatile struct avr32_usart_t * usart, int c)
{
        while (usart_write_char(usart, c) != USART_SUCCESS) {
        }

        return;
}

int usart_write_char(volatile struct avr32_usart_t * usart, int c)
{

        if ((usart->csr & (1<<AVR32_USART_CSR_TXRDY_OFFSET)) != 0) {
                usart->thr = c;
                return USART_SUCCESS;
        }
        else
                return USART_TX_BUSY;
}


int usart_read_char(volatile struct avr32_usart_t * usart, int * c)
{
        /* Check for errors; Frame, parity and overrun In RS485 mode a parity
                error would mean that we received an address char */
        if (usart->csr &
                        ((1 << AVR32_USART_CSR_OVRE_OFFSET) |
                        (1 << AVR32_USART_CSR_FRAME_OFFSET) |
                        (1 << AVR32_USART_CSR_PARE_OFFSET))) {
                return USART_RX_ERROR;
        }
        /* No error; if we really did receive a char, read it and return SUCCESS */
        else if ((usart->csr & (1<<AVR32_USART_CSR_RXRDY_OFFSET)) != 0) {
                *c = (unsigned short)usart->rhr;
                return USART_SUCCESS;
        } else {
                return USART_RX_EMPTY;
        }
} /* usart_read */


int usart_getchar(volatile struct avr32_usart_t * usart)
{
        int c, ret;

        while (((ret = usart_read_char(usart, &c)) == USART_RX_EMPTY)) {
        }

        if (ret == USART_RX_ERROR)
                return -1;
        else
                return c;
}


int usart_putchar(volatile struct avr32_usart_t * usart, int c)
{
        int timeout = USART_DEFAULT_TIMEOUT;

        if (c == '\n'){
          while ((usart_write_char(usart, '\r') != USART_SUCCESS) && (timeout>0) ){
            timeout--;
          }
        
          if (timeout == 0)
            return -1;
          timeout = USART_DEFAULT_TIMEOUT;
        }

        while ((usart_write_char(usart, c) != USART_SUCCESS) && ( timeout>0 )){
          timeout--;
        }
        if (timeout == 0)
                return -1;
        else
                return 0;
}

---