Modem emulator for "Datenklo" with AM7910/AM7911 emulation
This commit is contained in:
Andreas Eversberg
166
src/datenklo/uart.c
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166
src/datenklo/uart.c
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/* Software UART
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*
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* (C) 2019 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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#include "../libdebug/debug.h"
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#include "uart.h"
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static uint32_t calc_parity(uint32_t data, uint8_t data_bits, enum uart_parity parity)
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{
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int i;
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for (i = 0; i < data_bits; i++)
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parity |= (data >> i);
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parity &= 1;
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switch (parity) {
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case UART_PARITY_NONE:
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case UART_PARITY_SPACE:
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return 0;
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case UART_PARITY_MARK:
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return 1;
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case UART_PARITY_EVEN:
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return parity;
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case UART_PARITY_ODD:
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return parity ^ 1;
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}
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return 0; /* never reached */
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}
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int uart_init(uart_t *uart, void *inst, uint8_t data_bits, enum uart_parity parity, uint8_t stop_bits, int (*tx_cb)(void *inst), void (*rx_cb)(void *inst, int data, uint32_t flags))
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{
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memset(uart, 0, sizeof(*uart));
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uart->inst = inst;
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uart->tx_cb = tx_cb;
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uart->rx_cb = rx_cb;
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uart->data_bits = data_bits;
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if (uart->data_bits > 9) {
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PDEBUG(DUART, DEBUG_ERROR, "Illegal number of data bits, please fix!\n");
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abort();
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}
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uart->parity = parity;
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uart->stop_bits = stop_bits;
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if (uart->stop_bits < 1 || uart->stop_bits > 2) {
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PDEBUG(DUART, DEBUG_ERROR, "Illegal number of stop bits, please fix!\n");
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abort();
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}
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uart->tx_pos = -1;
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uart->rx_pos = -1;
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uart->length = uart->stop_bits + !!uart->parity + uart->data_bits;
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return 0;
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}
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/* called by modulator to get next bit from uart */
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int uart_tx_bit(uart_t *uart)
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{
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uint32_t bit, parity;
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if (uart->tx_pos < 0) {
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/* no transmission, get data */
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uart->tx_data = uart->tx_cb(uart->inst);
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/* return 1, if no data has not be sent */
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if (uart->tx_data > 0x7fffffff)
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return 1;
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/* all bits after data are stop bits */
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uart->tx_data |= 0xffffffff << uart->data_bits;
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/* calculate parity */
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if (uart->parity)
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parity = calc_parity(uart->tx_data, uart->data_bits, uart->parity);
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/* add parity bit */
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if (uart->parity) {
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/* erase bit for parity */
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uart->tx_data ^= 1 << uart->data_bits;
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/* put parity bit */
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uart->tx_data |= parity << uart->data_bits;
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}
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/* start with the first bit */
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uart->tx_pos = 0;
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/* return start bit */
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return 0;
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}
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/* get bit to be send */
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bit = (uart->tx_data >> uart->tx_pos) & 1;
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/* go to next bit and set tx_pos to -1, if there is no more bit */
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if (++uart->tx_pos == uart->length)
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uart->tx_pos = -1;
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/* return bit */
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return bit;
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}
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int uart_is_tx(uart_t *uart)
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{
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if (uart->tx_pos >= 0)
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return 1;
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return 0;
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}
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/* called by demodulator to indicate bit for uart */
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void uart_rx_bit(uart_t *uart, int bit)
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{
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uint32_t flags = 0;
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uint32_t parity;
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bit &= 1;
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/* if no data is receivd, check for start bit */
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if (uart->rx_pos < 0) {
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/* if no start bit */
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if (bit != 0 || uart->last_bit != 1)
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goto out;
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/* start bit */
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uart->rx_data = 0;
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uart->rx_pos = 0;
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return;
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}
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/* shift bit */
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uart->rx_data |= bit << (uart->rx_pos);
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/* end of transmission */
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if (++uart->rx_pos == uart->length) {
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/* turn off reception */
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uart->rx_pos = -1;
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/* check if parity is invalid */
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if (uart->parity) {
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parity = calc_parity(uart->rx_data, uart->data_bits, uart->parity);
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if (((uart->rx_data >> uart->data_bits) & 1) != parity)
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flags |= UART_PARITY_ERROR;
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}
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/* check if last stop bit is invalid */
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if (((uart->rx_data >> (uart->length - 1)) & 1) == 0) {
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flags |= UART_CODE_VIOLATION;
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}
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/* check if all bits are 0 */
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if (!uart->rx_data) {
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flags |= UART_BREAK;
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}
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/* clear all bits after data */
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uart->rx_data &= ~(0xffffffff << uart->data_bits);
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uart->rx_cb(uart->inst, uart->rx_data, flags);
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}
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out:
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/* remember last bit for start bit detection (1 -> 0 transition) */
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uart->last_bit = bit;
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}
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