freeswitch/libs/openzap/src/dsp/uart.c

/*
 *	uart.c
 *
 *	Copyright (c) 2005 Robert Krten.  All Rights Reserved.
 *
 *	Redistribution and use in source and binary forms, with or without
 *	modification, are permitted provided that the following conditions
 *	are met:
 *
 *	1. Redistributions of source code must retain the above copyright
 *	   notice, this list of conditions and the following disclaimer.
 *	2. Redistributions in binary form must reproduce the above copyright
 *	   notice, this list of conditions and the following disclaimer in the
 *	   documentation and/or other materials provided with the distribution.
 *
 *	THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
 *	ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *	IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *	ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE
 *	FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *	DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 *	OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *	HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *	LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *	OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *	SUCH DAMAGE.
 *
 *	This module contains a simple 8-bit UART, which performs a callback
 *	with the decoded byte value.
 *
 *	2005 06 11	R. Krten		created
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include "uart.h"

/*
 *	dsp_uart_attr_init
 *
 *	Initializes the attributes structure; this must be done before the
 *	attributes structure is used.
*/

void
dsp_uart_attr_init (dsp_uart_attr_t *attr)
{
	memset (attr, 0, sizeof (*attr));
}

/*
 *	dsp_uart_attr_get_bytehandler
 *	dsp_uart_attr_set_bytehandler
 *
 *	These functions get and set their respective elements from the
 *	attributes structure.  If an error code is returned, it is just
 *	zero == ok, -1 == fail.
*/

void (*
dsp_uart_attr_get_bytehandler (dsp_uart_attr_t *attr, void **bytehandler_arg)) (void *, int)
{
	*bytehandler_arg = attr -> bytehandler_arg;
	return (attr -> bytehandler);
}

void
dsp_uart_attr_set_bytehandler (dsp_uart_attr_t *attr, void (*bytehandler) (void *, int ), void *bytehandler_arg)
{
	attr -> bytehandler = bytehandler;
	attr -> bytehandler_arg = bytehandler_arg;
}

dsp_uart_handle_t *
dsp_uart_create (dsp_uart_attr_t *attr)
{
	dsp_uart_handle_t	*handle;

	handle = malloc (sizeof (*handle));
	if (handle == NULL) {
		return (handle);
	}
	memset (handle, 0, sizeof (handle));

	// fill the attributes member
	memcpy (&handle -> attr, attr, sizeof (*attr));

	return (handle);
}

void
dsp_uart_bit_handler (void *x, int bit)
{
	dsp_uart_handle_t *handle = (dsp_uart_handle_t *) x;

//	printf ("bit %d handle -> have_start %d handle -> data %02X handle -> nbits %d\n", bit, handle -> have_start, handle -> data, handle -> nbits);
	if (!handle -> have_start) {
		if (bit) {
			return;		// waiting for start bit (0)
		}
		handle -> have_start = 1;
		handle -> data = 0;
		handle -> nbits = 0;
		return;
	}

	handle -> data >>= 1;
	handle -> data |= 0x80 * !!bit;
	
	handle -> nbits++;
	if (handle -> nbits == 8) {
		(*handle -> attr.bytehandler) (handle -> attr.bytehandler_arg, handle -> data);
		handle -> nbits = 0;
		handle -> data = 0;
		handle -> have_start = 0;

// might consider handling errors in the future...
#if 0
	} else if (handle -> nbits > 8) {
		if (!bit) {
			// framing error; expected stop bit (mark, 1)
			printf ("FRAME"); fflush (stdout);
		} else {
			handle -> have_start = 0;
			handle -> nbits = 0;
		}
#endif
	}
}