vesc_packet.cpp

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/* 
 * This file is part of the arduino vesc library (https://github.com/arduino_vesc)
 * 
 * Copyright (c) 2019 Gianmarco Vitelli
 * 
 * This program is free software: you can redistribute it and/or modify  
 * it under the terms of the GNU General Public License as published by  
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License 
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <Arduino.h>
#include <HardwareSerial.h>
#include "vesc_packet.h"
 
void VescPacket::send_packet(HardwareSerial *port, unsigned char *data, unsigned int len)
{
  uint8_t tx_buffer[600];
 
  if (len == 0 || len > 255)
  {
    return;
  }
 
  int b_ind = 0;
 
  if (len <= 512)
  {
    tx_buffer[b_ind++] = 2;
    tx_buffer[b_ind++] = len;
  }
  else if (len <= 65535)
  {
    tx_buffer[b_ind++] = 3;
    tx_buffer[b_ind++] = len >> 8;
    tx_buffer[b_ind++] = len & 0xFF;
  }
  else
  {
    tx_buffer[b_ind++] = 4;
    tx_buffer[b_ind++] = len >> 16;
    tx_buffer[b_ind++] = (len >> 8) & 0x0F;
    tx_buffer[b_ind++] = len & 0xFF;
  }
 
  memcpy(tx_buffer + b_ind, data, len);
  b_ind += len;
 
  unsigned short crc = crc16(data, len);
  tx_buffer[b_ind++] = (uint8_t)(crc >> 8);
  tx_buffer[b_ind++] = (uint8_t)(crc & 0xFF);
  tx_buffer[b_ind++] = 3;
 
  port->write(tx_buffer, b_ind);
  port->flush();
}
 
bool VescPacket::receive_packet(HardwareSerial *port, unsigned char *data)
{
 
  for (; port->available() == 0;)
  {
    delay(100);
  }
 
  unsigned char rx_buffer[600];
  int b_ind = 0;
  int type = rx_buffer[b_ind++] = port->read();
 
  uint8_t len;
  switch (type)
  {
  case 2:
    len = rx_buffer[b_ind++] = port->read();
    break;
  case 3:
    len = (rx_buffer[b_ind++] = port->read()) << 8 |
          (rx_buffer[b_ind++] = port->read());
    break;
  case 4:
    len = (rx_buffer[b_ind++] = port->read()) << 16 |
          (rx_buffer[b_ind++] = port->read()) << 8 |
          (rx_buffer[b_ind++] = port->read());
    break;
  default:
    return false;
  }
 
  for (int i = 0; i < len; i++)
  {
    rx_buffer[b_ind++] = port->read();
  }
  
  unsigned short crc_calc = crc16(rx_buffer + type, len);
  unsigned short crc_rx = (unsigned short)(rx_buffer[len + 2] = port->read()) << 8 | (unsigned short) port->read();
  unsigned short packet_end = (rx_buffer[len + 3] = port->read());
  if (crc_calc == crc_rx && packet_end == 3)
  {
    memcpy(data, rx_buffer + type, len);
    return true;
  }
 
  return false;
}
 
const unsigned short crc16_tab[] = {0x0000, 0x1021, 0x2042, 0x3063, 0x4084,
                                    0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad,
                                    0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7,
                                    0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
                                    0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a,
                                    0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672,
                                    0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719,
                                    0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7,
                                    0x0840, 0x1861, 0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948,
                                    0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50,
                                    0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b,
                                    0xab1a, 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
                                    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97,
                                    0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe,
                                    0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca,
                                    0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3,
                                    0x5004, 0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d,
                                    0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214,
                                    0x6277, 0x7256, 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c,
                                    0xc50d, 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
                                    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3,
                                    0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d,
                                    0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806,
                                    0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e,
                                    0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1,
                                    0x1ad0, 0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b,
                                    0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0,
                                    0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
                                    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0};
 
unsigned short VescPacket::crc16(unsigned char *buf, unsigned int len)
{
  unsigned int i;
  unsigned short cksum = 0;
  for (i = 0; i < len; i++)
  {
    cksum = crc16_tab[(((cksum >> 8) ^ *buf++) & 0xFF)] ^ (cksum << 8);
  }
  return cksum;
}