Diff: ait_link.cpp

Revision:

0:8e8dfc870cb2

Child:

3:bfc4928cd279

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ait_link.cpp	Mon Apr 04 11:19:55 2016 +0000
@@ -0,0 +1,158 @@
+// Adapted by Benjamin Hepp from ArduHDLC library
+
+/*
+Arduhdlc is Arduino HDLC library, which can be used over any interface.
+Copyright (C) 2015 Jarkko Hautakorpi et al. see LICENSE.txt
+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; either version 2
+of the License, or (at your option) any later version.
+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, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*/
+
+
+#include "ait_link/ait_link.h"
+
+using namespace ait;
+
+/* 16bit low and high bytes copier */
+#define low(x)    ((x) & 0xFF)
+#define high(x)   (((x)>>8) & 0xFF)
+
+AITLink::AITLink(size_t max_frame_length)
+{
+  frame_checksum = CRC16_CCITT_INIT_VAL;
+  escape_character = false;
+  frame_position = 0;
+  this->max_frame_length = max_frame_length;
+  receive_frame_buffer = new uint8_t[max_frame_length+1]; // char* ab = (char*)malloc(12);
+  handle_frame_callback = NULL;
+  callback_user_data = NULL;
+}
+
+AITLink::~AITLink()
+{
+  delete[] receive_frame_buffer;
+}
+
+/* Wrap given data in HDLC frame and send it out byte at a time*/
+bool AITLink::sendFrame(const uint8_t* frame_buffer, size_t frame_length)
+{
+  if (frame_length > max_frame_length) {
+    return false;
+  }
+
+  uint8_t data;
+  uint16_t fcs = CRC16_CCITT_INIT_VAL;
+
+  sendChar(FRAME_BOUNDARY_OCTET);
+
+  while (frame_length)
+  {
+    data = *frame_buffer++;
+    fcs = crcCcittUpdate(fcs, data);
+    if ((data == CONTROL_ESCAPE_OCTET) || (data == FRAME_BOUNDARY_OCTET))
+    {
+      sendChar(CONTROL_ESCAPE_OCTET);
+      data ^= INVERT_OCTET;
+    }
+    sendChar(data);
+    --frame_length;
+  }
+  data = low(fcs);
+  if ((data == CONTROL_ESCAPE_OCTET) || (data == FRAME_BOUNDARY_OCTET))
+  {
+    sendChar(CONTROL_ESCAPE_OCTET);
+    data ^= INVERT_OCTET;
+  }
+  sendChar(data);
+  data = high(fcs);
+  if ((data == CONTROL_ESCAPE_OCTET) || (data == FRAME_BOUNDARY_OCTET))
+  {
+    sendChar(CONTROL_ESCAPE_OCTET);
+    data ^= INVERT_OCTET;
+  }
+  sendChar(data);
+  sendChar(FRAME_BOUNDARY_OCTET);
+
+  return true;
+}
+
+/* Function to find valid HDLC frame from incoming data */
+void AITLink::inputReceivedChar(uint8_t data)
+{
+  /* FRAME FLAG */
+  if (data == FRAME_BOUNDARY_OCTET)
+  {
+    if (this->escape_character == true)
+    {
+      this->escape_character = false;
+    }
+      /* If a valid frame is detected */
+    else if ( (this->frame_position >= 2) &&
+              ( this->frame_checksum == ((this->receive_frame_buffer[this->frame_position-1] << 8 ) | (this->receive_frame_buffer[this->frame_position-2] & 0xff)) ) )  // (msb << 8 ) | (lsb & 0xff)
+    {
+      /* Call the user defined function and pass frame to it */
+      handleFrame(receive_frame_buffer, this->frame_position - 2);
+    }
+    this->frame_position = 0;
+    this->frame_checksum = CRC16_CCITT_INIT_VAL;
+    return;
+  }
+
+  if (this->escape_character)
+  {
+    this->escape_character = false;
+    data ^= INVERT_OCTET;
+  }
+  else if (data == CONTROL_ESCAPE_OCTET)
+  {
+    this->escape_character = true;
+    return;
+  }
+
+  receive_frame_buffer[this->frame_position] = data;
+
+  if (this->frame_position >= 2) {
+    this->frame_checksum = crcCcittUpdate(this->frame_checksum, receive_frame_buffer[this->frame_position - 2]);
+  }
+
+  this->frame_position++;
+
+  if (this->frame_position >= this->max_frame_length)
+  {
+    this->frame_position = 0;
+    this->frame_checksum = CRC16_CCITT_INIT_VAL;
+  }
+}
+
+void AITLink::registerFrameHandler(void (*callback)(void* user_data, const uint8_t* frame_buffer, size_t frame_length), void* user_data)
+{
+  handle_frame_callback = callback;
+  callback_user_data = user_data;
+}
+
+void AITLink::handleFrame(const uint8_t* frame_buffer, size_t frame_length)
+{
+  if (handle_frame_callback != NULL) {
+    (*handle_frame_callback)(callback_user_data, frame_buffer, frame_length);
+  }
+
+}
+
+uint16_t AITLink::crcCcittUpdate(uint16_t crc, uint8_t data)
+{
+  data ^= low(crc);
+  data ^= data << 4;
+
+  return (
+          ( ((uint16_t)data << 8) | high(crc) ) ^ ((uint8_t)data >> 4) ^ ((uint16_t)data << 3)
+  );
+}
+