avr_serial.c

/**********************************************************************
 *
 * serial.c - Driver del UART del atmega328p
 *
 * Configuracion: 9600bps, 8bits data, 1bit stop, sin bit de paridad
 *
 **********************************************************************/

#include <stdint.h> /* para los tipos de datos. Ej.: uint8_t */
#include <avr/pgmspace.h>

typedef struct
{
        uint8_t status_control_a;    /* ucsr0a USART Control and Status A */
        uint8_t status_control_b;    /* ucsr0b USART Control and Status B */
        uint8_t status_control_c;    /* ucsr0c USART Control and Status C */
        uint8_t _reserved;           /* espacio sin utilizar */
        uint8_t baud_rate_l;         /* ubrr0l baud rate low */
        uint8_t baud_rate_h;         /* ubrr0h baud rate high */
        uint8_t data_es;             /* udr0 i/o data */
} volatile uart_t;

/* puntero a la estructura de los registros del periferico */
uart_t *puerto_serial = (uart_t *) (0xc0);

#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU/(USART_BAUDRATE*16UL)))-1) 
/* F_CPU viene como parametro en el Makefile */

/* UCSRnC */

/* the UCSZn bits combined with the UCSZn2 bit in UCSRnB sets the number of data bits */
/* in a frame the receiver and transmitter use */
#define FRAME_SIZE_0 0x02  /* 0b 0000 0010 - bit 1 */
#define FRAME_SIZE_1 0x04  /* 0b 0000 0100 - bit 2 */

/* USBSn (bit 3) selects the number of stop bits to be inserted by the transmitter (0 is 1 bit) */
/* UPMn these bits set the type of parity generation and check (0 and 0 is disabled) */

/* UCSRnB */

/* the RXENn bit if set to one enables the USART receiver */
#define RECEIVER_ENABLE 0x10  /* 0b 0001 0000 - bit 4  */

/* the TXENn bit if set to one enables the USART transmitter */
#define TRANSMITTER_ENABLE 0x08  /* 0b 0000 1000 - bit 3 */

/* UCSRnA */

/* the RXCn bit is set when there are unread data in the receive buffer */
/* and cleared when the receibe buffer is empty (ie does not contain any unread data */
#define READY_TO_READ 0x80  /* 0b 1000 0000 - bit 7 */

/* the UDREn flag indicates if the transmit buffer is ready to receive new data */
/* if UDREn is one, the buffer is empty and therefore ready to be written */
#define READY_TO_WRITE 0x20  /* 0b 0010 0000 - bit 5 */


void serial_init()
{
        /* Configurar los registros High y Low con BAUD_PRESCALE */
        puerto_serial->baud_rate_h = (unsigned char) (BAUD_PRESCALE>>8);
        puerto_serial->baud_rate_l = (unsigned char) (BAUD_PRESCALE);
        /* Configurar un frame de 8bits, sin bit de paridad y un bit de stop */
        puerto_serial->status_control_c = (unsigned char) (FRAME_SIZE_0 | FRAME_SIZE_1);
        /* Activar la recepcion y transmision */
        puerto_serial->status_control_b = (unsigned char) (RECEIVER_ENABLE | TRANSMITTER_ENABLE);
}


/* enviar un byte a traves del dispositivo inicializado */
void serial_put_char(char c)
{
        /* Wait until the transmitter is ready for the next character. */
        while ( !((puerto_serial->status_control_a) & (READY_TO_WRITE)) );
        /* Send the character via the serial port. */
        puerto_serial->data_es = c;
}


char serial_get_char(void)
{
        /* Wait for the next character to arrive. */
        while ( !((puerto_serial->status_control_a) & (READY_TO_READ)) );
        return (puerto_serial->data_es);
}

void serial_put_str2(const __flash char m[])
{
	int i;
	for (i=0; i<strlen_P(m); i++)
                serial_put_char(m[i]);

        serial_put_char('\r');
        serial_put_char('\n');
}

void serial_put_str(char * str)
{
        while (*str) {
                serial_put_char(*str);
                str++;
        }

        serial_put_char('\r');
        serial_put_char('\n');
}