usart.c

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/*This file has been prepared for Doxygen automatic documentation generation.*/
#include "usart.h"

void usart_reset( volatile 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 avr32_usart_t * usart,
                unsigned int baudrate,
                long cpuHz)
{
        int cd, fp; /* clock divider and fractional part */

        /*
         *             ** BAUDRATE CALCULATION **
         *
         *                 selected clock                       selected clock
         *     baudrate = ----------------   or     baudrate = ----------------
         *                16 x (CD + FP/8)                      8 x (CD + FP/8)
         *
         *       (with 16x oversampling)              (with 8x oversampling)
         */
        if( baudrate > (cpuHz/16) ) {
                /* use 8x oversampling */
                usart->mr |= (1<<AVR32_USART_MR_OVER_OFFSET);
                cd = cpuHz / ( 8 * baudrate );

                if( cd < 2 ) {
                        return USART_ERROR_ARGUMENT;
                }

                fp = cpuHz / baudrate - 8 * cd;
                usart->brgr = (cd << AVR32_USART_BRGR_CD_OFFSET);
        } else {
                /* use 16x oversampling */
                usart->mr &= ~(1<<AVR32_USART_MR_OVER_OFFSET);
                cd = cpuHz / ( 16 * baudrate );

                if( cd > 65535 ) {
                        /* wanted baudrate is too low */
                        return USART_ERROR_ARGUMENT;
                }

                fp = cpuHz / ( 2 * baudrate ) - 8 * cd;
                usart->brgr = (cd << AVR32_USART_BRGR_CD_OFFSET);
        }

        return USART_OK;
}


int usart_init2( volatile avr32_usart_t * usart,
                struct usart_options_t * opt,
                long cpuHz )
{
        int retval;

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

        /* control input values */
        if( opt == 0 ) {
                return USART_ERROR_ARGUMENT;
        }
        if( opt->charlength < 5 || opt->charlength > 9 ) {
                return USART_ERROR_ARGUMENT;
        }
        if( opt->paritytype > 7 ) {
                return USART_ERROR_ARGUMENT;
        }
        if( opt->stopbits > 2+255 ) {
                return USART_ERROR_ARGUMENT;
        }
        if( opt->channelmode > 3 ) {
                return USART_ERROR_ARGUMENT;
        }

        retval = usart_set_baudrate( usart, opt->baudrate, cpuHz );

        if( retval != USART_OK ) {
                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);
        }

        /* enable TX and RX */
        usart->cr |= (1<<AVR32_USART_CR_TXEN_OFFSET) |
                     (1<<AVR32_USART_CR_RXEN_OFFSET);

        return USART_OK;
}


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

        do {
                --timeout;
        } while( (usart->csr & (1<<AVR32_USART_CSR_TXRDY_OFFSET)) == 0 && timeout > 0 );

        if( timeout == 0 ) {
                return USART_TX_BUSY;
        }

        usart->thr = character;

        return USART_OK;
}


int usart_writeLine( volatile avr32_usart_t * usart, char * string )
{
        int retVal = USART_OK;

        while( *string != '\0' ) {
                retVal = usart_putchar( usart, *string++ );
        }

        if( retVal != USART_OK ) {
                return retVal;
        }

        return USART_OK;
}

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