DistantIO

Diff: protocol.cpp

Revision:

0:c4676d32d381

Child:

1:aaffeb93f99b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/protocol.cpp	Tue Sep 15 15:27:55 2015 +0000
@@ -0,0 +1,155 @@
+/*
+ * serial_protocol.c
+ *
+ *  Created on: Oct 22, 2014
+ *      Author: B48923
+ */
+
+#include "protocol.h"
+
+enum state
+{
+	IDLE,
+	IN_PROCESS
+};
+typedef enum state state;
+
+
+enum ESC_state
+{
+	NONE,
+	NEXT
+};
+typedef enum ESC_state ESC_state;
+
+uint16_t decodingIndex;
+state protocol_state;
+ESC_state escape_state;
+
+uint8_t SOF_;
+uint8_t EOF_;
+uint8_t ESC_;
+
+static void (*on_encoding_done)(uint8_t* data, uint16_t size);
+static void (*on_decoding_done)(uint8_t* data, uint16_t size);
+
+
+void init_protocol(void (*encoding_done_callback)(uint8_t*,uint16_t),void (*decoding_done_callback)(uint8_t*,uint16_t))
+{
+	protocol_state = IDLE;
+	escape_state = NONE;
+	
+	SOF_ = 0xF7;
+	EOF_ = 0x7F;
+	ESC_ = 0x7D;
+
+	decodingIndex = 0;
+	
+	on_encoding_done = encoding_done_callback;
+	on_decoding_done = decoding_done_callback;
+}
+
+void encode(uint8_t* framedata, uint16_t framesize)
+{
+	// If frame size is superior than maximum allowed, abort
+	if(framesize > ENCODING_BUFFER_SIZE)
+		return;
+
+	// Actual buffer size is twice the data size (for worst case byte stuffing) + SOF + EOF
+	static uint8_t encodingBuffer[ENCODING_BUFFER_SIZE * 2 + 2];
+
+	uint16_t index = 0, i = 0;
+	
+	//Write start of frame / end of frame byte
+	encodingBuffer[index++] = SOF_;
+	
+	//Write data
+	for(i = 0 ; i < framesize ; i++)
+	{
+		//See serial_protocols_definition.xlsx
+		if(*(framedata + i) == SOF_ ||
+		   *(framedata + i) == EOF_ ||
+		   *(framedata + i) == ESC_)
+		{
+			//If data contains one of the flags, we escape it before
+			encodingBuffer[index++] = ESC_;
+		}
+		encodingBuffer[index++] = framedata[i];
+	}
+	
+	encodingBuffer[index++] = EOF_;
+
+	// Operation is done, call function callback
+	on_encoding_done(encodingBuffer,index);
+}
+
+void decode(uint8_t received_byte)
+{
+	static uint8_t decodingBuffer[DECODING_BUFFER_SIZE];
+
+	// If a reception was in process
+	if(protocol_state == IN_PROCESS)
+	{
+		// If the character was previously marked as pure data
+		if(escape_state == NEXT)
+		{
+			// If max buffer size was reached, cancel reception to avoid overflowing buffer
+			if(decodingIndex + 1 >= DECODING_BUFFER_SIZE)
+			{
+				decodingIndex = 0;
+				protocol_state = IDLE;
+				escape_state = NONE;
+			}
+			else
+			{
+				decodingBuffer[decodingIndex++] = received_byte;
+				escape_state = NONE;
+			}
+		}
+		else
+		{
+			// End of frame
+			if(received_byte == EOF_)
+			{
+				protocol_state = IDLE;
+				// Call the function callback for end of frame
+				on_decoding_done(decodingBuffer,decodingIndex);
+			}
+			else if(received_byte == ESC_)
+			{
+				escape_state = NEXT;
+			}
+			else
+			{
+				// If max buffer size was reached, cancel reception to avoid overflowing buffer
+				if(decodingIndex + 1 >= DECODING_BUFFER_SIZE)
+				{
+					decodingIndex = 0;
+					protocol_state = IDLE;
+					escape_state = NONE;
+				}
+				else
+				{
+					decodingBuffer[decodingIndex++] = received_byte;
+					escape_state = NONE;
+				}
+			}
+		}
+	}
+	else
+	{
+		if(received_byte == SOF_)
+		{
+			protocol_state = IN_PROCESS;
+			decodingIndex = 0;
+			escape_state = NONE;
+		}
+		else
+		{
+			//Received character outside a valid frame, ignore it
+		}
+	}
+}
+
+
+