mirror of
https://github.com/Keychron/qmk_firmware.git
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140 lines
3.6 KiB
C
140 lines
3.6 KiB
C
/*
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Copyright 2012 Jun WAKO <wakojun@gmail.com>
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This software is licensed with a Modified BSD License.
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All of this is supposed to be Free Software, Open Source, DFSG-free,
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GPL-compatible, and OK to use in both free and proprietary applications.
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Additions and corrections to this file are welcome.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of the copyright holders nor the names of
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <stdbool.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <util/delay.h>
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#include "serial.h"
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/*
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* Stupid Inefficient Busy-wait Software Serial
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* is still useful for negative logic signal like Sun protocol not supported by hardware USART.
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*/
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#define WAIT_US (1000000/SERIAL_BAUD)
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void serial_init(void)
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{
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SERIAL_RXD_INIT();
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SERIAL_TXD_INIT();
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}
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/* RX ring buffer */
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#define RBUF_SIZE 8
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static uint8_t rbuf[RBUF_SIZE];
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static uint8_t rbuf_head = 0;
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static uint8_t rbuf_tail = 0;
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uint8_t serial_recv(void)
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{
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uint8_t data = 0;
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if (rbuf_head == rbuf_tail) {
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return 0;
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}
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data = rbuf[rbuf_tail];
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rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
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return data;
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}
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void serial_send(uint8_t data)
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{
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/* signal state: IDLE: ON, START: OFF, STOP: ON, DATA0: OFF, DATA1: ON */
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/* start bit */
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SERIAL_TXD_OFF();
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_delay_us(WAIT_US);
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#ifdef SERIAL_BIT_ORDER_MSB
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uint8_t mask = 0x80;
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#else
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uint8_t mask = 0x01;
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#endif
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while (mask) {
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if (data&mask) { SERIAL_TXD_ON(); } else { SERIAL_TXD_OFF(); }
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_delay_us(WAIT_US);
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#ifdef SERIAL_BIT_ORDER_MSB
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mask >>= 1;
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#else
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mask <<= 1;
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#endif
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}
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/* stop bit */
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SERIAL_TXD_ON();
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_delay_us(WAIT_US);
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}
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/* detect edge of start bit */
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ISR(SERIAL_RXD_VECT)
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{
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SERIAL_RXD_INT_ENTER()
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uint8_t data = 0;
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#ifdef SERIAL_BIT_ORDER_MSB
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uint8_t mask = 0x80;
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#else
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uint8_t mask = 0x01;
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#endif
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/* to center of start bit */
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_delay_us(WAIT_US/2);
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do {
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/* to center of next bit */
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_delay_us(WAIT_US);
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if (SERIAL_RXD_READ()) {
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data |= mask;
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}
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#ifdef SERIAL_BIT_ORDER_MSB
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mask >>= 1;
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#else
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mask <<= 1;
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#endif
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} while (mask);
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/* to center of stop bit */
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_delay_us(WAIT_US);
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uint8_t next = (rbuf_head + 1) % RBUF_SIZE;
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if (next != rbuf_tail) {
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rbuf[rbuf_head] = data;
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rbuf_head = next;
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}
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SERIAL_RXD_INT_EXIT();
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}
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