/*********************************************************************************
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* Copyright: (C) 2022 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: packet.c
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* Description: This file is packet API functions
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*
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* Version: 1.0.0(18/04/22)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "18/04/22 16:30:25"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <time.h>
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#include "packet.h"
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#include "logger.h"
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#include "ds18b20.h"
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int get_devid(char *devid, int size, int sn)
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{
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if( !devid || size<DEVID_LEN )
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{
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log_error("Invalid input arugments\n");
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return -1;
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}
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memset(devid, 0, size);
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snprintf(devid, size, "rpi#%04d", sn);
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return 0;
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}
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int get_time(struct tm *ptm)
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{
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if( !ptm )
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{
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log_error("Invalid input arugments\n");
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return -1;
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}
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time_t now = time(NULL);
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localtime_r(&now, ptm);
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return 0;
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}
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int packet_segmented_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
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{
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char strtime[TIME_LEN] = {'\0'};
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struct tm *ptm;
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char *buf = (char *)pack_buf;
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if( !pack_info || !buf || size<=0 )
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{
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log_error("Invalid input arguments\n");
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return -1;
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}
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ptm = &pack_info->sample_time;
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snprintf(strtime, sizeof(strtime), "%04d-%02d-%02d %02d:%02d:%02d",
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ptm->tm_year+1900, ptm->tm_mon+1, ptm->tm_mday,
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ptm->tm_hour, ptm->tm_min, ptm->tm_sec);
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memset(buf, 0, size);
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snprintf(buf, size, "%s|%s|%.3f", pack_info->devid, strtime, pack_info->temper);
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return strlen(buf);
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}
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int packet_json_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
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{
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char strtime[TIME_LEN] = {'\0'};
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struct tm *ptm;
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char *buf = (char *)pack_buf;
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if( !pack_info || !buf || size<=0 )
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{
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log_error("Invalid input arguments\n");
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return -1;
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}
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ptm = &pack_info->sample_time;
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snprintf(strtime, sizeof(strtime), "%04d-%02d-%2d %02d:%02d:%02d",
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ptm->tm_year+1900, ptm->tm_mon+1, ptm->tm_mday,
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ptm->tm_hour, ptm->tm_min, ptm->tm_sec);
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memset(buf, 0, size);
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snprintf(buf, size, "{\"devid\":\"%s\", \"time\":\"%s\",\"temperature\":\"%.3f\"}",
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pack_info->devid, strtime, pack_info->temper);
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return strlen(buf);
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}
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/*
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* The CRC-ITU-T, also known as CRC-16-ITU-T or CRC-16-V.41, uses the polynomial:
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* 0x1021: x^16 + x^12 + x^5 + 1
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*/
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#define CRC16_ITU_T_POLY 0x1021 /* Define the CRC-ITU-T polynomial */
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static uint16_t crc_itu_t(const uint8_t *data, size_t length)
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{
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uint16_t crc = 0xFFFF;
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size_t i, j;
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for (i=0; i<length; i++)
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{
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crc ^= ((uint16_t)data[i] << 8);
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for(j=0; j<8; j++)
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{
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if (crc & 0x8000)
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{
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crc = (crc << 1) ^ CRC16_ITU_T_POLY;
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}
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else
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{
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crc <<= 1;
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}
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}
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}
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return crc;
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}
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uint16_t to_big_endian(uint16_t num)
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{
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return (num << 8) | (num >> 8);
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}
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/* TLV(Tag Length Value) PDU(Protocal Data Unit) format:
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*
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* +-----------+-----------+------------+-------------+-------------+
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* | Header(2B)| Tag(1B) | Length(2B) | Value(nB) | CRC16(2B) |
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* +-----------+-----------+------------+-------------+-------------+
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*
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* Header(2B): 0xFE 0xFD
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* Tag(1B): 0x01->temperature 0x02->Humidity 0x03->Noisy ...
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* Length(2B): Data value length
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* Value(nB): Data value
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* CRC16(2B): CRC from Header to Value
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*/
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int packet_tlv_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
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{
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struct tm *ptm;
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int ofset = 0;
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uint16_t crc;
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if( !pack_info || !pack_buf || size<TLV_MINSIZE )
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{
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log_error("Invalid input arguments\n");
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return -1;
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}
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/*+----------------------+
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*| TLV Header(2B) |
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*+----------------------+*/
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*(uint16_t *)pack_buf = to_big_endian(TLV_HEADER);
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ofset += 2;
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/*+----------------------+
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*| TLV Tag(1B) |
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*+----------------------+*/
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pack_buf[ofset++] = TAG_TEMPERATURE;
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/* Skip data length here, we will calculate it later */
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ofset += 2;
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/*+----------------------+
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*| payload data value |
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*+----------------------+*/
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/* 6 bytes sample time */
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ptm = &pack_info->sample_time;
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pack_buf[ofset++] = (uint8_t)(ptm->tm_year+1900-2000);
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pack_buf[ofset++] = (uint8_t)(ptm->tm_mon+1);
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pack_buf[ofset++] = (uint8_t)(ptm->tm_mday);
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pack_buf[ofset++] = (uint8_t)(ptm->tm_hour);
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pack_buf[ofset++] = (uint8_t)(ptm->tm_min);
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pack_buf[ofset++] = (uint8_t)(ptm->tm_sec);
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/* 8 bytes device SN */
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strncpy((char *)(pack_buf+ofset), pack_info->devid, DEVID_LEN);
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ofset += DEVID_LEN;
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/* 2 bytes temperature value */
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pack_buf[ofset++] = (int)pack_info->temper; /* integer part */
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pack_buf[ofset++] = (((int)(pack_info->temper*100))%100); /* fractional part */
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/*+----------------------+
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*| TLV Length(2B) |
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*+----------------------+*/
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*(uint16_t *)(pack_buf+3) = (ofset-5);
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/*+----------------------+
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*| TLV CRC(2B) |
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*+----------------------+*/
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crc = crc_itu_t(pack_buf, ofset);
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*(uint16_t *)(pack_buf+ofset) = crc;
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ofset += 2;
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return ofset;
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}
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