open_source / modbus

  /*
   * Copyright © 2001-2011 Stéphane Raimbault <stephane.raimbault@gmail.com>
   *
   * SPDX-License-Identifier: LGPL-2.1+
   */

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

  #ifndef _MSC_VER

  #include <unistd.h>

  #endif

  #include <assert.h>
  
  #include "modbus-private.h"
  
  #include "modbus-rtu.h"
  #include "modbus-rtu-private.h"
  
  #if HAVE_DECL_TIOCSRS485 || HAVE_DECL_TIOCM_RTS
  #include <sys/ioctl.h>
  #endif
  
  #if HAVE_DECL_TIOCSRS485
  #include <linux/serial.h>
  #endif
  
  /* Table of CRC values for high-order byte */
  static const uint8_t table_crc_hi[] = {
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
      0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
      0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
      0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
      0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
      0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
      0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
      0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
      0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
      0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
      0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
      0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
      0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
      0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
      0x80, 0x41, 0x00, 0xC1, 0x81, 0x40
  };
  
  /* Table of CRC values for low-order byte */
  static const uint8_t table_crc_lo[] = {
      0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,
      0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
      0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
      0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,
      0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,
      0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
      0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
      0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,
      0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
      0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,
      0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,
      0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
      0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,
      0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
      0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
      0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
      0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,
      0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
      0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,
      0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,
      0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
      0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,
      0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
      0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
      0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,
      0x43, 0x83, 0x41, 0x81, 0x80, 0x40
  };
  
  /* Define the slave ID of the remote device to talk in master mode or set the
   * internal slave ID in slave mode */

  static int _modbus_set_slave(modbus_t *ctx, int slave)

  {
      /* Broadcast address is 0 (MODBUS_BROADCAST_ADDRESS) */

      if (slave >= 0 && slave <= 247) {

          ctx->slave = slave;

      } else {

          errno = EINVAL;
          return -1;
      }
  
      return 0;
  }
  
  /* Builds a RTU request header */

  static int _modbus_rtu_build_request_basis(modbus_t *ctx, int function,
                                             int addr, int nb,
                                             uint8_t *req)

  {
      assert(ctx->slave != -1);
      req[0] = ctx->slave;
      req[1] = function;
      req[2] = addr >> 8;
      req[3] = addr & 0x00ff;
      req[4] = nb >> 8;
      req[5] = nb & 0x00ff;
  
      return _MODBUS_RTU_PRESET_REQ_LENGTH;
  }
  
  /* Builds a RTU response header */

  static int _modbus_rtu_build_response_basis(sft_t *sft, uint8_t *rsp)

  {
      /* In this case, the slave is certainly valid because a check is already
       * done in _modbus_rtu_listen */
      rsp[0] = sft->slave;
      rsp[1] = sft->function;
  
      return _MODBUS_RTU_PRESET_RSP_LENGTH;
  }
  

  static uint16_t crc16(uint8_t *buffer, uint16_t buffer_length)

  {

      uint8_t crc_hi = 0xFF; /* high CRC byte initialized */
      uint8_t crc_lo = 0xFF; /* low CRC byte initialized */
      unsigned int i; /* will index into CRC lookup */

  
      /* pass through message buffer */
      while (buffer_length--) {
          i = crc_hi ^ *buffer++; /* calculate the CRC  */
          crc_hi = crc_lo ^ table_crc_hi[i];
          crc_lo = table_crc_lo[i];
      }
  
      return (crc_hi << 8 | crc_lo);
  }
  

  static int _modbus_rtu_prepare_response_tid(const uint8_t *req, int *req_length)

  {
      (*req_length) -= _MODBUS_RTU_CHECKSUM_LENGTH;
      /* No TID */
      return 0;
  }
  

  static int _modbus_rtu_send_msg_pre(uint8_t *req, int req_length)

  {

      uint16_t crc = crc16(req, req_length);

      req[req_length++] = crc >> 8;
      req[req_length++] = crc & 0x00FF;
  
      return req_length;
  }
  

  #if defined(_WIN32)
  
  /* This simple implementation is sort of a substitute of the select() call,
   * working this way: the win32_ser_select() call tries to read some data from
   * the serial port, setting the timeout as the select() call would. Data read is
   * stored into the receive buffer, that is then consumed by the win32_ser_read()
   * call.  So win32_ser_select() does both the event waiting and the reading,
   * while win32_ser_read() only consumes the receive buffer.
   */
  
  static void win32_ser_init(struct win32_ser *ws)
  {
      /* Clear everything */
      memset(ws, 0x00, sizeof(struct win32_ser));
  
      /* Set file handle to invalid */
      ws->fd = INVALID_HANDLE_VALUE;
  }
  
  /* FIXME Try to remove length_to_read -> max_len argument, only used by win32 */
  static int win32_ser_select(struct win32_ser *ws, int max_len,
                              const struct timeval *tv)
  {
      COMMTIMEOUTS comm_to;
      unsigned int msec = 0;
  
      /* Check if some data still in the buffer to be consumed */
      if (ws->n_bytes > 0) {
          return 1;
      }
  
      /* Setup timeouts like select() would do.
         FIXME Please someone on Windows can look at this?
         Does it possible to use WaitCommEvent?
         When tv is NULL, MAXDWORD isn't infinite!
       */
      if (tv == NULL) {
          msec = MAXDWORD;
      } else {
          msec = tv->tv_sec * 1000 + tv->tv_usec / 1000;
          if (msec < 1)
              msec = 1;
      }
  
      comm_to.ReadIntervalTimeout = msec;
      comm_to.ReadTotalTimeoutMultiplier = 0;
      comm_to.ReadTotalTimeoutConstant = msec;
      comm_to.WriteTotalTimeoutMultiplier = 0;
      comm_to.WriteTotalTimeoutConstant = 1000;
      SetCommTimeouts(ws->fd, &comm_to);
  
      /* Read some bytes */
      if ((max_len > PY_BUF_SIZE) || (max_len < 0)) {
          max_len = PY_BUF_SIZE;
      }
  
      if (ReadFile(ws->fd, &ws->buf, max_len, &ws->n_bytes, NULL)) {
          /* Check if some bytes available */
          if (ws->n_bytes > 0) {
              /* Some bytes read */
              return 1;
          } else {
              /* Just timed out */
              return 0;
          }
      } else {
          /* Some kind of error */
          return -1;
      }
  }
  
  static int win32_ser_read(struct win32_ser *ws, uint8_t *p_msg,
                            unsigned int max_len)
  {
      unsigned int n = ws->n_bytes;
  
      if (max_len < n) {
          n = max_len;
      }
  
      if (n > 0) {
          memcpy(p_msg, ws->buf, n);
      }
  
      ws->n_bytes -= n;
  
      return n;
  }
  #endif
  

  #if HAVE_DECL_TIOCM_RTS

  static void _modbus_rtu_ioctl_rts(modbus_t *ctx, int on)

  {
      int fd = ctx->s;
      int flags;
  
      ioctl(fd, TIOCMGET, &flags);

      if (on) {

          flags |= TIOCM_RTS;

      } else {

          flags &= ~TIOCM_RTS;
      }
      ioctl(fd, TIOCMSET, &flags);
  }
  #endif
  

  static ssize_t _modbus_rtu_send(modbus_t *ctx, const uint8_t *req, int req_length)

  {

  #if defined(_WIN32)
      modbus_rtu_t *ctx_rtu = ctx->backend_data;
      DWORD n_bytes = 0;
      return (WriteFile(ctx_rtu->w_ser.fd, req, req_length, &n_bytes, NULL)) ? (ssize_t)n_bytes : -1;
  #else

  #if HAVE_DECL_TIOCM_RTS
      modbus_rtu_t *ctx_rtu = ctx->backend_data;

      if (ctx_rtu->rts != MODBUS_RTU_RTS_NONE) {

          ssize_t size;
  
          if (ctx->debug) {
              fprintf(stderr, "Sending request using RTS signal\n");
          }
  
          ctx_rtu->set_rts(ctx, ctx_rtu->rts == MODBUS_RTU_RTS_UP);
          usleep(ctx_rtu->rts_delay);
  
          size = write(ctx->s, req, req_length);
  
          usleep(ctx_rtu->onebyte_time * req_length + ctx_rtu->rts_delay);
          ctx_rtu->set_rts(ctx, ctx_rtu->rts != MODBUS_RTU_RTS_UP);
  
          return size;

      } else {

  #endif
          return write(ctx->s, req, req_length);
  #if HAVE_DECL_TIOCM_RTS
      }
  #endif

  #endif

  }
  

  static int _modbus_rtu_receive(modbus_t *ctx, uint8_t *req)

  {
      int rc;
      modbus_rtu_t *ctx_rtu = ctx->backend_data;
  

      if (ctx_rtu->confirmation_to_ignore) {

          _modbus_receive_msg(ctx, req, MSG_CONFIRMATION);
          /* Ignore errors and reset the flag */
          ctx_rtu->confirmation_to_ignore = FALSE;
          rc = 0;

          if (ctx->debug) {

              printf("Confirmation to ignore\n");
          }

      } else {
          rc = _modbus_receive_msg(ctx, req, MSG_INDICATION);
          if (rc == 0) {

              /* The next expected message is a confirmation to ignore */
              ctx_rtu->confirmation_to_ignore = TRUE;
          }
      }
      return rc;
  }
  

  static ssize_t _modbus_rtu_recv(modbus_t *ctx, uint8_t *rsp, int rsp_length)

  {

  #if defined(_WIN32)
      return win32_ser_read(&((modbus_rtu_t *)ctx->backend_data)->w_ser, rsp, rsp_length);
  #else

      return read(ctx->s, rsp, rsp_length);

  #endif

  }
  
  static int _modbus_rtu_flush(modbus_t *);
  

  static int _modbus_rtu_pre_check_confirmation(modbus_t *ctx, const uint8_t *req,
                                                const uint8_t *rsp, int rsp_length)

  {

      /* Check responding slave is the slave we requested (except for broacast
       * request) */
      if (req[0] != rsp[0] && req[0] != MODBUS_BROADCAST_ADDRESS) {
          if (ctx->debug) {
              fprintf(stderr,
                      "The responding slave %d isn't the requested slave %d\n",
                      rsp[0], req[0]);

          }
          errno = EMBBADSLAVE;
          return -1;

      } else {
          return 0;
      }

  }
  
  /* The check_crc16 function shall return 0 is the message is ignored and the
     message length if the CRC is valid. Otherwise it shall return -1 and set
     errno to EMBADCRC. */

  static int _modbus_rtu_check_integrity(modbus_t *ctx, uint8_t *msg,
                                         const int msg_length)

  {
      uint16_t crc_calculated;
      uint16_t crc_received;
      int slave = msg[0];
  
      /* Filter on the Modbus unit identifier (slave) in RTU mode to avoid useless
       * CRC computing. */

      if (slave != ctx->slave && slave != MODBUS_BROADCAST_ADDRESS) {
          if (ctx->debug) {

              printf("Request for slave %d ignored (not %d)\n", slave, ctx->slave);
          }
          /* Following call to check_confirmation handles this error */
          return 0;
      }
  
      crc_calculated = crc16(msg, msg_length - 2);
      crc_received = (msg[msg_length - 2] << 8) | msg[msg_length - 1];
  
      /* Check CRC of msg */

      if (crc_calculated == crc_received) {

          return msg_length;

      } else {
          if (ctx->debug) {

              fprintf(stderr, "ERROR CRC received 0x%0X != CRC calculated 0x%0X\n",
                      crc_received, crc_calculated);
          }
  

          if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {

              _modbus_rtu_flush(ctx);
          }
          errno = EMBBADCRC;
          return -1;
      }
  }
  
  /* Sets up a serial port for RTU communications */
  static int _modbus_rtu_connect(modbus_t *ctx)
  {

  #if defined(_WIN32)
      DCB dcb;
  #else

      struct termios tios;
      speed_t speed;
      int flags;

  #endif

      modbus_rtu_t *ctx_rtu = ctx->backend_data;
  

      if (ctx->debug) {

          printf("Opening %s at %d bauds (%c, %d, %d)\n",

                 ctx_rtu->device, ctx_rtu->baud, ctx_rtu->parity,
                 ctx_rtu->data_bit, ctx_rtu->stop_bit);
      }
  
  #if defined(_WIN32)
      /* Some references here:
       * http://msdn.microsoft.com/en-us/library/aa450602.aspx
       */
      win32_ser_init(&ctx_rtu->w_ser);
  
      /* ctx_rtu->device should contain a string like "COMxx:" xx being a decimal
       * number */
      ctx_rtu->w_ser.fd = CreateFileA(ctx_rtu->device,
                                      GENERIC_READ | GENERIC_WRITE,
                                      0,
                                      NULL,
                                      OPEN_EXISTING,
                                      0,
                                      NULL);
  
      /* Error checking */
      if (ctx_rtu->w_ser.fd == INVALID_HANDLE_VALUE) {
          if (ctx->debug) {
              fprintf(stderr, "ERROR Can't open the device %s (LastError %d)\n",
                      ctx_rtu->device, (int)GetLastError());
          }
          return -1;
      }
  
      /* Save params */
      ctx_rtu->old_dcb.DCBlength = sizeof(DCB);
      if (!GetCommState(ctx_rtu->w_ser.fd, &ctx_rtu->old_dcb)) {
          if (ctx->debug) {
              fprintf(stderr, "ERROR Error getting configuration (LastError %d)\n",
                      (int)GetLastError());
          }
          CloseHandle(ctx_rtu->w_ser.fd);
          ctx_rtu->w_ser.fd = INVALID_HANDLE_VALUE;
          return -1;

      }
  

      /* Build new configuration (starting from current settings) */
      dcb = ctx_rtu->old_dcb;
  
      /* Speed setting */
      switch (ctx_rtu->baud) {
      case 110:
          dcb.BaudRate = CBR_110;
          break;
      case 300:
          dcb.BaudRate = CBR_300;
          break;
      case 600:
          dcb.BaudRate = CBR_600;
          break;
      case 1200:
          dcb.BaudRate = CBR_1200;
          break;
      case 2400:
          dcb.BaudRate = CBR_2400;
          break;
      case 4800:
          dcb.BaudRate = CBR_4800;
          break;
      case 9600:
          dcb.BaudRate = CBR_9600;
          break;
      case 14400:
          dcb.BaudRate = CBR_14400;
          break;
      case 19200:
          dcb.BaudRate = CBR_19200;
          break;
      case 38400:
          dcb.BaudRate = CBR_38400;
          break;
      case 57600:
          dcb.BaudRate = CBR_57600;
          break;
      case 115200:
          dcb.BaudRate = CBR_115200;
          break;
      case 230400:
          /* CBR_230400 - not defined */
          dcb.BaudRate = 230400;
          break;
      case 250000:
          dcb.BaudRate = 250000;
          break;
      case 460800:
          dcb.BaudRate = 460800;
          break;
      case 500000:
          dcb.BaudRate = 500000;
          break;
      case 921600:
          dcb.BaudRate = 921600;
          break;
      case 1000000:
          dcb.BaudRate = 1000000;
          break;
      default:
          dcb.BaudRate = CBR_9600;
          if (ctx->debug) {
              fprintf(stderr, "WARNING Unknown baud rate %d for %s (B9600 used)\n",
                      ctx_rtu->baud, ctx_rtu->device);
          }
      }
  
      /* Data bits */
      switch (ctx_rtu->data_bit) {
      case 5:
          dcb.ByteSize = 5;
          break;
      case 6:
          dcb.ByteSize = 6;
          break;
      case 7:
          dcb.ByteSize = 7;
          break;
      case 8:
      default:
          dcb.ByteSize = 8;
          break;
      }
  
      /* Stop bits */
      if (ctx_rtu->stop_bit == 1)
          dcb.StopBits = ONESTOPBIT;
      else /* 2 */
          dcb.StopBits = TWOSTOPBITS;
  
      /* Parity */
      if (ctx_rtu->parity == 'N') {
          dcb.Parity = NOPARITY;
          dcb.fParity = FALSE;
      } else if (ctx_rtu->parity == 'E') {
          dcb.Parity = EVENPARITY;
          dcb.fParity = TRUE;
      } else {
          /* odd */
          dcb.Parity = ODDPARITY;
          dcb.fParity = TRUE;
      }
  
      /* Hardware handshaking left as default settings retrieved */
  
      /* No software handshaking */
      dcb.fTXContinueOnXoff = TRUE;
      dcb.fOutX = FALSE;
      dcb.fInX = FALSE;
  
      /* Binary mode (it's the only supported on Windows anyway) */
      dcb.fBinary = TRUE;
  
      /* Don't want errors to be blocking */
      dcb.fAbortOnError = FALSE;
  
  	//***Not part of libmodbus - added for QModMaster***//
      dcb.fRtsControl = ctx_rtu->rts;
  	
      /* Setup port */
      if (!SetCommState(ctx_rtu->w_ser.fd, &dcb)) {
          if (ctx->debug) {
              fprintf(stderr, "ERROR Error setting new configuration (LastError %d)\n",
                      (int)GetLastError());
          }
          CloseHandle(ctx_rtu->w_ser.fd);
          ctx_rtu->w_ser.fd = INVALID_HANDLE_VALUE;
          return -1;
      }
  #else

      /* The O_NOCTTY flag tells UNIX that this program doesn't want
         to be the "controlling terminal" for that port. If you
         don't specify this then any input (such as keyboard abort
         signals and so forth) will affect your process
  
         Timeouts are ignored in canonical input mode or when the
         NDELAY option is set on the file via open or fcntl */
      flags = O_RDWR | O_NOCTTY | O_NDELAY | O_EXCL;
  #ifdef O_CLOEXEC
      flags |= O_CLOEXEC;
  #endif
  
      ctx->s = open(ctx_rtu->device, flags);
      if (ctx->s == -1) {
          if (ctx->debug) {
              fprintf(stderr, "ERROR Can't open the device %s (%s)\n",
                      ctx_rtu->device, strerror(errno));
          }
          return -1;
      }
  
      /* Save */
      tcgetattr(ctx->s, &ctx_rtu->old_tios);
  
      memset(&tios, 0, sizeof(struct termios));
  
      /* C_ISPEED     Input baud (new interface)
         C_OSPEED     Output baud (new interface)
      */

      switch (ctx_rtu->baud) {

      case 110:
          speed = B110;
          break;
      case 300:
          speed = B300;
          break;
      case 600:
          speed = B600;
          break;
      case 1200:
          speed = B1200;
          break;
      case 2400:
          speed = B2400;
          break;
      case 4800:
          speed = B4800;
          break;
      case 9600:
          speed = B9600;
          break;
      case 19200:
          speed = B19200;
          break;
      case 38400:
          speed = B38400;
          break;
  #ifdef B57600
      case 57600:
          speed = B57600;
          break;
  #endif
  #ifdef B115200
      case 115200:
          speed = B115200;
          break;
  #endif
  #ifdef B230400
      case 230400:
          speed = B230400;
          break;
  #endif
  #ifdef B460800
      case 460800:
          speed = B460800;
          break;
  #endif
  #ifdef B500000
      case 500000:
          speed = B500000;
          break;
  #endif
  #ifdef B576000
      case 576000:
          speed = B576000;
          break;
  #endif
  #ifdef B921600
      case 921600:
          speed = B921600;
          break;
  #endif
  #ifdef B1000000
      case 1000000:
          speed = B1000000;
          break;
  #endif
  #ifdef B1152000
     case 1152000:
          speed = B1152000;
          break;
  #endif
  #ifdef B1500000
      case 1500000:
          speed = B1500000;
          break;
  #endif
  #ifdef B2500000
      case 2500000:
          speed = B2500000;
          break;
  #endif
  #ifdef B3000000
      case 3000000:
          speed = B3000000;
          break;
  #endif
  #ifdef B3500000
      case 3500000:
          speed = B3500000;
          break;
  #endif
  #ifdef B4000000
      case 4000000:
          speed = B4000000;
          break;
  #endif
      default:
          speed = B9600;
          if (ctx->debug) {
              fprintf(stderr,
                      "WARNING Unknown baud rate %d for %s (B9600 used)\n",
                      ctx_rtu->baud, ctx_rtu->device);
          }
      }
  
      /* Set the baud rate */
      if ((cfsetispeed(&tios, speed) < 0) ||
          (cfsetospeed(&tios, speed) < 0)) {
          close(ctx->s);
          ctx->s = -1;
          return -1;
      }
  
      /* C_CFLAG      Control options
         CLOCAL       Local line - do not change "owner" of port
         CREAD        Enable receiver
      */
      tios.c_cflag |= (CREAD | CLOCAL);
      /* CSIZE, HUPCL, CRTSCTS (hardware flow control) */
  
      /* Set data bits (5, 6, 7, 8 bits)
         CSIZE        Bit mask for data bits
      */
      tios.c_cflag &= ~CSIZE;
      switch (ctx_rtu->data_bit) {
      case 5:
          tios.c_cflag |= CS5;
          break;
      case 6:
          tios.c_cflag |= CS6;
          break;
      case 7:
          tios.c_cflag |= CS7;
          break;
      case 8:
      default:
          tios.c_cflag |= CS8;
          break;
      }
  
      /* Stop bit (1 or 2) */
      if (ctx_rtu->stop_bit == 1)
          tios.c_cflag &=~ CSTOPB;
      else /* 2 */
          tios.c_cflag |= CSTOPB;
  
      /* PARENB       Enable parity bit
         PARODD       Use odd parity instead of even */
      if (ctx_rtu->parity == 'N') {
          /* None */
          tios.c_cflag &=~ PARENB;
      } else if (ctx_rtu->parity == 'E') {
          /* Even */
          tios.c_cflag |= PARENB;
          tios.c_cflag &=~ PARODD;
      } else {
          /* Odd */
          tios.c_cflag |= PARENB;
          tios.c_cflag |= PARODD;
      }
  
      /* Read the man page of termios if you need more information. */
  
      /* This field isn't used on POSIX systems
         tios.c_line = 0;
      */
  
      /* C_LFLAG      Line options
  
         ISIG Enable SIGINTR, SIGSUSP, SIGDSUSP, and SIGQUIT signals
         ICANON       Enable canonical input (else raw)
         XCASE        Map uppercase \lowercase (obsolete)
         ECHO Enable echoing of input characters
         ECHOE        Echo erase character as BS-SP-BS
         ECHOK        Echo NL after kill character
         ECHONL       Echo NL
         NOFLSH       Disable flushing of input buffers after
         interrupt or quit characters
         IEXTEN       Enable extended functions
         ECHOCTL      Echo control characters as ^char and delete as ~?
         ECHOPRT      Echo erased character as character erased
         ECHOKE       BS-SP-BS entire line on line kill
         FLUSHO       Output being flushed
         PENDIN       Retype pending input at next read or input char
         TOSTOP       Send SIGTTOU for background output
  
         Canonical input is line-oriented. Input characters are put
         into a buffer which can be edited interactively by the user
         until a CR (carriage return) or LF (line feed) character is
         received.
  
         Raw input is unprocessed. Input characters are passed
         through exactly as they are received, when they are
         received. Generally you'll deselect the ICANON, ECHO,
         ECHOE, and ISIG options when using raw input
      */
  
      /* Raw input */
      tios.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
  
      /* C_IFLAG      Input options
  
         Constant     Description
         INPCK        Enable parity check
         IGNPAR       Ignore parity errors
         PARMRK       Mark parity errors
         ISTRIP       Strip parity bits
         IXON Enable software flow control (outgoing)
         IXOFF        Enable software flow control (incoming)
         IXANY        Allow any character to start flow again
         IGNBRK       Ignore break condition
         BRKINT       Send a SIGINT when a break condition is detected
         INLCR        Map NL to CR
         IGNCR        Ignore CR
         ICRNL        Map CR to NL
         IUCLC        Map uppercase to lowercase
         IMAXBEL      Echo BEL on input line too long
      */
      if (ctx_rtu->parity == 'N') {
          /* None */
          tios.c_iflag &= ~INPCK;
      } else {
          tios.c_iflag |= INPCK;
      }
  
      /* Software flow control is disabled */
      tios.c_iflag &= ~(IXON | IXOFF | IXANY);
  
      /* C_OFLAG      Output options
         OPOST        Postprocess output (not set = raw output)
         ONLCR        Map NL to CR-NL
  
         ONCLR ant others needs OPOST to be enabled
      */
  
      /* Raw ouput */
      tios.c_oflag &=~ OPOST;
  
      /* C_CC         Control characters
         VMIN         Minimum number of characters to read
         VTIME        Time to wait for data (tenths of seconds)
  
         UNIX serial interface drivers provide the ability to
         specify character and packet timeouts. Two elements of the
         c_cc array are used for timeouts: VMIN and VTIME. Timeouts
         are ignored in canonical input mode or when the NDELAY
         option is set on the file via open or fcntl.
  
         VMIN specifies the minimum number of characters to read. If
         it is set to 0, then the VTIME value specifies the time to
         wait for every character read. Note that this does not mean
         that a read call for N bytes will wait for N characters to
         come in. Rather, the timeout will apply to the first
         character and the read call will return the number of
         characters immediately available (up to the number you
         request).
  
         If VMIN is non-zero, VTIME specifies the time to wait for
         the first character read. If a character is read within the
         time given, any read will block (wait) until all VMIN
         characters are read. That is, once the first character is
         read, the serial interface driver expects to receive an
         entire packet of characters (VMIN bytes total). If no
         character is read within the time allowed, then the call to
         read returns 0. This method allows you to tell the serial
         driver you need exactly N bytes and any read call will
         return 0 or N bytes. However, the timeout only applies to
         the first character read, so if for some reason the driver
         misses one character inside the N byte packet then the read
         call could block forever waiting for additional input
         characters.
  
         VTIME specifies the amount of time to wait for incoming
         characters in tenths of seconds. If VTIME is set to 0 (the
         default), reads will block (wait) indefinitely unless the
         NDELAY option is set on the port with open or fcntl.
      */
      /* Unused because we use open with the NDELAY option */
      tios.c_cc[VMIN] = 0;

      tios.c_cc[VTIME] = 0;

  
      if (tcsetattr(ctx->s, TCSANOW, &tios) < 0) {
          close(ctx->s);
          ctx->s = -1;
          return -1;
      }

  #endif
  

      return 0;
  }
  
  int modbus_rtu_set_serial_mode(modbus_t *ctx, int mode)
  {
      if (ctx == NULL) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCSRS485
          modbus_rtu_t *ctx_rtu = ctx->backend_data;
          struct serial_rs485 rs485conf;
          memset(&rs485conf, 0x0, sizeof(struct serial_rs485));
  
          if (mode == MODBUS_RTU_RS485) {
              rs485conf.flags = SER_RS485_ENABLED;
              if (ioctl(ctx->s, TIOCSRS485, &rs485conf) < 0) {
                  return -1;
              }
  
              ctx_rtu->serial_mode = MODBUS_RTU_RS485;
              return 0;
          } else if (mode == MODBUS_RTU_RS232) {
              /* Turn off RS485 mode only if required */
              if (ctx_rtu->serial_mode == MODBUS_RTU_RS485) {
                  /* The ioctl call is avoided because it can fail on some RS232 ports */
                  if (ioctl(ctx->s, TIOCSRS485, &rs485conf) < 0) {
                      return -1;
                  }
              }
              ctx_rtu->serial_mode = MODBUS_RTU_RS232;
              return 0;
          }
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      }
  
      /* Wrong backend and invalid mode specified */
      errno = EINVAL;
      return -1;
  }
  
  int modbus_rtu_get_serial_mode(modbus_t *ctx)
  {
      if (ctx == NULL) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCSRS485
          modbus_rtu_t *ctx_rtu = ctx->backend_data;
          return ctx_rtu->serial_mode;
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      } else {
          errno = EINVAL;
          return -1;
      }
  }
  
  int modbus_rtu_get_rts(modbus_t *ctx)
  {
      if (ctx == NULL) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCM_RTS
          modbus_rtu_t *ctx_rtu = ctx->backend_data;
          return ctx_rtu->rts;
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      } else {
          errno = EINVAL;
          return -1;
      }
  }
  
  int modbus_rtu_set_rts(modbus_t *ctx, int mode)
  {
      if (ctx == NULL) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCM_RTS
          modbus_rtu_t *ctx_rtu = ctx->backend_data;
  
          if (mode == MODBUS_RTU_RTS_NONE || mode == MODBUS_RTU_RTS_UP ||
              mode == MODBUS_RTU_RTS_DOWN) {
              ctx_rtu->rts = mode;
  
              /* Set the RTS bit in order to not reserve the RS485 bus */
              ctx_rtu->set_rts(ctx, ctx_rtu->rts != MODBUS_RTU_RTS_UP);
  
              return 0;
          } else {
              errno = EINVAL;
              return -1;
          }
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      }
      /* Wrong backend or invalid mode specified */
      errno = EINVAL;
      return -1;
  }
  
  int modbus_rtu_set_custom_rts(modbus_t *ctx, void (*set_rts) (modbus_t *ctx, int on))
  {
      if (ctx == NULL) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCM_RTS
          modbus_rtu_t *ctx_rtu = ctx->backend_data;
          ctx_rtu->set_rts = set_rts;
          return 0;
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      } else {
          errno = EINVAL;
          return -1;
      }
  }
  
  int modbus_rtu_get_rts_delay(modbus_t *ctx)
  {
      if (ctx == NULL) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCM_RTS
          modbus_rtu_t *ctx_rtu;
          ctx_rtu = (modbus_rtu_t *)ctx->backend_data;
          return ctx_rtu->rts_delay;
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      } else {
          errno = EINVAL;
          return -1;
      }
  }
  
  int modbus_rtu_set_rts_delay(modbus_t *ctx, int us)
  {
      if (ctx == NULL || us < 0) {
          errno = EINVAL;
          return -1;
      }
  
      if (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU) {
  #if HAVE_DECL_TIOCM_RTS
          modbus_rtu_t *ctx_rtu;
          ctx_rtu = (modbus_rtu_t *)ctx->backend_data;
          ctx_rtu->rts_delay = us;
          return 0;
  #else
          if (ctx->debug) {
              fprintf(stderr, "This function isn't supported on your platform\n");
          }
          errno = ENOTSUP;
          return -1;
  #endif
      } else {
          errno = EINVAL;
          return -1;
      }
  }
  
  static void _modbus_rtu_close(modbus_t *ctx)
  {
      /* Restore line settings and close file descriptor in RTU mode */
      modbus_rtu_t *ctx_rtu = ctx->backend_data;
  

  #if defined(_WIN32)
      /* Revert settings */
      if (!SetCommState(ctx_rtu->w_ser.fd, &ctx_rtu->old_dcb) && ctx->debug) {
          fprintf(stderr, "ERROR Couldn't revert to configuration (LastError %d)\n",
                  (int)GetLastError());
      }
  
      if (!CloseHandle(ctx_rtu->w_ser.fd) && ctx->debug) {
          fprintf(stderr, "ERROR Error while closing handle (LastError %d)\n",
                  (int)GetLastError());
      }
  #else