skarg
405 lines
13 KiB
C
405 lines
13 KiB
C
/**************************************************************************
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*
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* Copyright (C) 2007 Steve Karg <skarg@users.sourceforge.net>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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*********************************************************************/
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/* The module handles sending data out the RS-485 port */
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/* and handles receiving data from the RS-485 port. */
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/* Customize this file for your specific hardware */
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#include <stddef.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <stdio.h>
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//#include "mstp.h"
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/* This file has been customized for use with ATMEGA168 */
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#include "hardware.h"
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#include "timer.h"
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/* Timers for turning off the TX,RX LED indications */
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static uint8_t LED1_Off_Timer;
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static uint8_t LED3_Off_Timer;
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/* baud rate */
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static uint32_t RS485_Baud = 9600;
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/* autobaud - switch baud on errors if autobaud is true */
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static bool RS485_Autobaud = true;
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/* we saw some data, so we are on an active wire */
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static uint8_t RS485_Data_Count;
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/* count of errors before autobaud switching */
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static uint8_t RS485_Error_Count;
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/* time limit */
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#define RS485_ERROR_TIMEOUT 1000
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/* millisecond timer to limit error window */
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static uint16_t RS485_Error_Timer = RS485_ERROR_TIMEOUT;
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/* number of errors in 1000ms before autobaud switching */
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#define RS485_ERROR_LIMIT 30
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/* The minimum time after the end of the stop bit of the final octet of a */
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/* received frame before a node may enable its EIA-485 driver: 40 bit times. */
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/* At 9600 baud, 40 bit times would be about 4.166 milliseconds */
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/* At 19200 baud, 40 bit times would be about 2.083 milliseconds */
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/* At 38400 baud, 40 bit times would be about 1.041 milliseconds */
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/* At 57600 baud, 40 bit times would be about 0.694 milliseconds */
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/* At 76800 baud, 40 bit times would be about 0.520 milliseconds */
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/* At 115200 baud, 40 bit times would be about 0.347 milliseconds */
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/* 40 bits is 4 octets including a start and stop bit with each octet */
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#define Tturnaround (40UL)
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/* turnaround_time_milliseconds = (Tturnaround*1000UL)/RS485_Baud; */
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/* The maximum time after the end of the stop bit of the final */
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/* octet of a transmitted frame before a node must disable its */
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/* EIA-485 driver: 15 bit times. */
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/* NOTE: AVR lib delay_us limit is 768us; limit is 7bits/9600bps=729us */
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#define Tpostdrive1 (7UL)
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#define Tpostdrive2 (7UL)
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/****************************************************************************
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* DESCRIPTION: Initializes the RS485 hardware and variables, and starts in
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* receive mode.
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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void RS485_Initialize(void)
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{
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/* enable Transmit and Receive */
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UCSR0B = _BV(TXEN0) | _BV(RXEN0);
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/* Set USART Control and Status Register n C */
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/* Asynchronous USART 8-bit data, No parity, 1 stop */
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/* Set USART Mode Select: UMSELn1 UMSELn0 = 00 for Asynchronous USART */
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/* Set Parity Mode: UPMn1 UPMn0 = 00 for Parity Disabled */
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/* Set Stop Bit Select: USBSn = 0 for 1 stop bit */
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/* Set Character Size: UCSZn2 UCSZn1 UCSZn0 = 011 for 8-bit */
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/* Clock Polarity: UCPOLn = 0 when asynchronous mode is used. */
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UCSR0C = _BV(UCSZ01) | _BV(UCSZ00);
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/* Clear Power Reduction USART0 */
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BIT_CLEAR(PRR,PRUSART0);
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/* Use port PD2 for RTS - enable and disable of Transceiver Tx/Rx */
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/* Set port bit as Output - initially receiving */
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BIT_CLEAR(PORTD,PD2);
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BIT_SET(DDRD,DDD2);
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/* Configure Transmit and Receive LEDs - initially off */
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BIT_SET(PORTD,PD6);
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BIT_SET(PORTD,PD7);
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BIT_SET(DDRD,DDD6);
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BIT_SET(DDRD,DDD7);
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return;
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}
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/****************************************************************************
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* DESCRIPTION: Returns the baud rate that we are currently running at
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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uint32_t RS485_Get_Baud_Rate(void)
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{
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return RS485_Baud;
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}
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/****************************************************************************
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* DESCRIPTION: Sets the baud rate for the chip USART
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* RETURN: true if valid baud rate
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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bool RS485_Set_Baud_Rate(uint32_t baud)
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{
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bool valid = true;
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switch (baud) {
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case 9600:
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case 19200:
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case 38400:
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case 57600:
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case 76800:
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case 115200:
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RS485_Baud = baud;
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/* 2x speed mode */
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BIT_SET(UCSR0A,U2X0);
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/* configure baud rate */
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UBRR0 = (F_CPU / (8UL * RS485_Baud)) - 1;
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/* FIXME: store the baud rate */
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break;
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default:
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valid = false;
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break;
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}
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return valid;
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}
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void RS485_Next_Baud_Rate(void)
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{
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uint32_t baud;
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switch (RS485_Baud) {
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case 9600:
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baud = 19200;
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break;
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case 19200:
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baud = 38400;
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break;
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case 38400:
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baud = 57600;
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break;
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case 57600:
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baud = 76800;
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break;
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case 76800:
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baud = 115200;
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break;
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case 115200:
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default:
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baud = 9600;
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break;
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}
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RS485_Set_Baud_Rate(baud);
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}
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/****************************************************************************
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* DESCRIPTION: Waits on the SilenceTimer for 40 bits.
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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void RS485_Turnaround_Delay(void)
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{
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uint16_t turnaround_time;
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/* delay after reception before trasmitting - per MS/TP spec */
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/* wait a minimum 40 bit times since reception */
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/* at least 1 ms for errors: rounding, clock tick */
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turnaround_time = 1 + ((Tturnaround*1000UL)/RS485_Baud);
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while (Timer_Silence() < turnaround_time) {
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/* do nothing - wait for timer to increment */
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};
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}
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/****************************************************************************
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* DESCRIPTION: Enable or disable the transmitter
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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void RS485_Transmitter_Enable(bool enable)
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{
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if (enable) {
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BIT_SET(PORTD,PD2);
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} else {
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#if Tpostdrive1
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_delay_us(Tpostdrive1/RS485_Baud);
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#endif
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#if Tpostdrive2
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_delay_us(Tpostdrive2/RS485_Baud);
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#endif
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BIT_CLEAR(PORTD,PD2);
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}
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}
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/****************************************************************************
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* DESCRIPTION: Timers for delaying the LED indicators going off
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* RETURN: none
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* ALGORITHM: none
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* NOTES: expected to be called once a millisecond
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*****************************************************************************/
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void RS485_LED_Timers(void)
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{
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if (LED1_Off_Timer) {
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LED1_Off_Timer--;
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if (LED1_Off_Timer == 0) {
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BIT_SET(PORTD,PD6);
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}
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}
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if (LED3_Off_Timer) {
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LED3_Off_Timer--;
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if (LED3_Off_Timer == 0) {
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BIT_SET(PORTD,PD7);
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}
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}
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if (RS485_Error_Timer) {
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RS485_Error_Timer--;
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}
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}
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/****************************************************************************
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* DESCRIPTION: Turn on the LED, and set the off timer to turn it off
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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static void RS485_LED1_On(void)
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{
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BIT_CLEAR(PORTD,PD6);
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LED1_Off_Timer = 20;
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}
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/****************************************************************************
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* DESCRIPTION: Turn on the LED, and set the off timer to turn it off
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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static void RS485_LED3_On(void)
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{
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BIT_CLEAR(PORTD,PD7);
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LED3_Off_Timer = 20;
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}
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/****************************************************************************
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* DESCRIPTION: Send some data and wait until it is sent
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* RETURN: none
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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void RS485_Send_Data(
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uint8_t * buffer, /* data to send */
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uint16_t nbytes) /* number of bytes of data */
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{
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RS485_LED3_On();
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while (nbytes) {
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while (!BIT_CHECK(UCSR0A,UDRE0)) {
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/* do nothing - wait until Tx buffer is empty */
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}
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UDR0 = *buffer;
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buffer++;
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nbytes--;
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}
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while (!BIT_CHECK(UCSR0A,UDRE0)) {
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/* do nothing - wait until Tx buffer is empty */
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}
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/* is the frame sent? */
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while (!BIT_CHECK(UCSR0A,TXC0)) {
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/* do nothing - wait until the entire frame in the
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Transmit Shift Register has been shifted out */
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}
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BIT_CLEAR(UCSR0A,TXC0);
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/* per MSTP spec, sort of */
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Timer_Silence_Reset();
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}
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/****************************************************************************
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* DESCRIPTION: Return true if a framing or overrun error is present
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* RETURN: true if error
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* ALGORITHM: autobaud - if there are a lot of errors, switch baud rate
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* NOTES: Clears any error flags.
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*****************************************************************************/
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bool RS485_ReceiveError(void)
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{
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bool ReceiveError = false;
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uint8_t dummy_data;
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/* check for framing error */
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if (BIT_CHECK(UCSR0A,FE0)) {
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ReceiveError = true;
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}
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/* check for overrun error */
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if (BIT_CHECK(UCSR0A,DOR0)) {
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ReceiveError = true;
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}
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if (ReceiveError) {
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RS485_LED1_On();
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/* flush the receive buffer */
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do {
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dummy_data = UDR0;
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} while (BIT_CHECK(UCSR0A,RXC0));
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/* count errors during autobaud */
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if (RS485_Error_Count < RS485_ERROR_LIMIT) {
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RS485_Error_Count++;
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} else {
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if (RS485_Autobaud && RS485_Error_Timer) {
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/* We are in autobaud mode, and there were excessive
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errors while the timer was counting down */
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RS485_Next_Baud_Rate();
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RS485_Error_Timer = RS485_ERROR_TIMEOUT;
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RS485_Error_Count = 0;
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} else if (RS485_Autobaud) {
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/* autobaud, but timer expired */
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RS485_Autobaud = false;
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}
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}
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} else {
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if (RS485_Autobaud) {
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if ((RS485_Error_Timer == 0) && (RS485_Error_Count == 0)) {
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if (RS485_Data_Count > 8) {
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/* no errors, timer expired, and we saw data */
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RS485_Autobaud = false;
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} else {
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/* no errors, timer expired, and no data*/
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RS485_Error_Timer = RS485_ERROR_TIMEOUT;
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}
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}
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}
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}
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return ReceiveError;
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}
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/****************************************************************************
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* DESCRIPTION: Return true if data is available
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* RETURN: true if data is available, with the data in the parameter set
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* ALGORITHM: none
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* NOTES: none
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*****************************************************************************/
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bool RS485_DataAvailable(uint8_t *data)
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{
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bool DataAvailable = false;
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/* check for data */
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if (BIT_CHECK(UCSR0A,RXC0)) {
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*data = UDR0;
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DataAvailable = true;
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RS485_LED1_On();
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if (RS485_Data_Count < 0xFF)
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RS485_Data_Count++;
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}
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return DataAvailable;
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}
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#ifdef TEST_RS485
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int main(void)
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{
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unsigned i = 0;
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uint8_t DataRegister;
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RS485_Set_Baud_Rate(38400);
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RS485_Initialize();
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/* receive task */
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for (;;) {
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if (RS485_ReceiveError()) {
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fprintf(stderr,"ERROR ");
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} else if (RS485_DataAvailable(&DataRegister)) {
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fprintf(stderr,"%02X ",DataRegister);
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}
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}
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}
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#endif /* TEST_RS485 */
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