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773f69d5d9
NxModbus is a lightweight Modbus protocol stack implementation for NuttX RTOS. This commit adds: - nxmodbus stack - nxmbserver - Modbus Server (Slave) example - nxmbclient - Modbus Client (Master) tool Supported Modbus transports: - ASCII - RTU over serial port - TCP - RAW (ADU) for custom transport implementations Signed-off-by: raiden00pl <raiden00@railab.me>
70 lines
2.1 KiB
C
70 lines
2.1 KiB
C
/****************************************************************************
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* apps/industry/nxmodbus/transport/nxmb_lrc.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/compiler.h>
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#include <stdint.h>
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#include "nxmb_internal.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxmb_lrc
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*
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* Description:
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* Calculate Modbus ASCII LRC checksum.
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*
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* Input Parameters:
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* buf - Pointer to data buffer
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* len - Length of data in bytes
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*
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* Returned Value:
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* LRC value (8-bit)
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*
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****************************************************************************/
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uint8_t nxmb_lrc(FAR const uint8_t *buf, uint16_t len)
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{
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uint8_t lrc = 0;
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uint16_t i;
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if (buf == NULL || len == 0)
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{
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return lrc;
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}
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for (i = 0; i < len; i++)
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{
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lrc += buf[i];
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}
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return (uint8_t)(-((int8_t)lrc));
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}
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