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uart.c
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uart.c
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/*!
* Very simple software UART for AVR microcontrollers
* (C) 2016 Stuart Longland
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "uart.h"
#include "uartcfg.h"
#include <avr/io.h>
#include <util/delay.h>
#include <stdint.h>
#include <avr/pgmspace.h>
#define TX_BIT (1 << UART_TX_BIT)
#define BIT_US (1000000/UART_BAUD) /*!< Bit period in microseconds */
/*!
* Configure the UART pins.
*/
void uart_init() {
UART_TX_DDR |= TX_BIT;
UART_TX_PORT |= TX_BIT;
}
/*!
* Send a raw byte to the UART.
*/
void uart_tx(uint8_t byte) {
uint8_t mask = 1;
/* Start bit */
UART_TX_PORT &= ~TX_BIT; _delay_us(BIT_US);
while(mask) {
if (mask & byte)
UART_TX_PORT |= TX_BIT;
else
UART_TX_PORT &= ~TX_BIT;
_delay_us(BIT_US);
mask <<= 1;
}
/* Stop bit */
UART_TX_PORT |= TX_BIT; _delay_us(BIT_US);
}
/*!
* Send a text string (in pgmspace) to the UART.
* String shall be null-terminated!
*/
void uart_tx_str(const char* str) {
char c = pgm_read_byte(str);
while (c) {
str++;
uart_tx(c);
c = pgm_read_byte(str);
}
}
/*!
* Send a 4-bit nybble to the UART.
*/
void uart_tx_hex(uint8_t nybble) {
if (nybble >= 10)
uart_tx(nybble - 10 + 'a');
else
uart_tx(nybble + '0');
}
/*!
* Send a 8-bit byte to the UART.
*/
void uart_tx_hex_byte(uint8_t byte) {
uart_tx_hex(byte >> 4);
uart_tx_hex(byte & 0x0f);
}
/*!
* Send a 16-bit word to the UART.
*/
void uart_tx_hex_word(uint16_t word) {
uart_tx_hex_byte(word >> 8);
uart_tx_hex_byte(word & 0xff);
}
/*!
* Send a 32-bit long word to the UART.
*/
void uart_tx_hex_lword(uint32_t lword) {
uart_tx_hex_word(lword >> 16);
uart_tx_hex_word(lword & 0xffff);
}