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SerialDecoder.cs
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SerialDecoder.cs
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using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using LabNation.Interfaces;
namespace LabNation.Decoders
{
[Export(typeof(IDecoder))]
public class SerialDecoder : IDecoder
{
public const String BAUD_AUTO = "AUTO";
public const String BAUD_9600 = "9600";
public const double BAUD_9600_LENGTH = 0.000104;
public const String BAUD_19200 = "19200";
public const double BAUD_19200_LENGTH = 0.000052;
public const String BAUD_38400 = "38400";
public const double BAUD_38400_LENGTH = 0.000026;
public const String BAUD_57600 = "57600";
public const double BAUD_57600_LENGTH = 0.000017;
public const String BAUD_115200 = "115200";
public const double BAUD_115200_LENGTH = 0.0000085;
public const String PARITY_NONE = "NONE";
public const String PARITY_ODD = "ODD";
public const String PARITY_EVEN = "EVEN";
public class BitSet
{
private bool value;
private int count;
private int startIndex;
public bool Value {
get {
return this.value;
}
set {
this.value = value;
}
}
public int Count {
get {
return this.count;
}
set {
this.count = value;
}
}
public int StartIndex {
get {
return this.startIndex;
}
set {
this.startIndex = value;
}
}
public BitSet(bool value, int startIndex) {
this.Value = value;
this.StartIndex = startIndex;
}
public void Increment() {
Count++;
}
}
public DecoderDescription Description
{
get
{
return new DecoderDescription()
{
Name = "Serial Decoder",
ShortName = "UART",
Author = "P. Jaczewski",
VersionMajor = 0,
VersionMinor = 1,
Description = "A simple decoder to decode the serial (UART) communication",
InputWaveformTypes = new Dictionary<string, Type>()
{
{ "UART", typeof(bool)}
},
Parameters = new DecoderParameter[]
{
new DecoderParamaterStrings("BAUD", new String[] {BAUD_AUTO, BAUD_9600, BAUD_19200, BAUD_38400, BAUD_57600, BAUD_115200},
BAUD_AUTO, "Baud rate."),
new DecoderParamaterInts("BITS", new int[] {5, 6, 7, 8}, "bits", 8, "Number of bits."),
new DecoderParamaterInts("STOP", new int[] {1, 2}, "stop", 1, "Number of stop bits."),
new DecoderParamaterStrings("PARITY", new String[] {PARITY_NONE, PARITY_EVEN, PARITY_ODD}, PARITY_NONE, "Parity type.")
}
};
}
}
public DecoderOutput[] Decode(Dictionary<string, Array> inputWaveforms, Dictionary<string, object> parameters, double samplePeriod)
{
//name input waveforms for easier usage
bool[] UART = (bool[])inputWaveforms["UART"];
//initialize output structure
List<DecoderOutput> decoderOutputList = new List<DecoderOutput>();
// determine number of bits
int numberOfBits = (int) parameters ["BITS"];
// determine number of stop bits
int numberOfStopBits = (int) parameters ["STOP"];
// determine parity type
String parityType = (String) parameters ["PARITY"];
//determine bit length according to desired baud rate
double bitLength = 0;
String baud = (String)parameters ["BAUD"];
switch (baud)
{
case BAUD_115200:
{
bitLength = BAUD_115200_LENGTH;
break;
}
case BAUD_57600:
{
bitLength = BAUD_57600_LENGTH;
break;
}
case BAUD_38400:
{
bitLength = BAUD_38400_LENGTH;
break;
}
case BAUD_19200:
{
bitLength = BAUD_19200_LENGTH;
break;
}
case BAUD_9600:
{
bitLength = BAUD_9600_LENGTH;
break;
}
}
// begin decode for sample set
LinkedList<BitSet> values = new LinkedList<BitSet> ();
if (UART != null && UART.Length > 0) {
// find bit sets
for (int i = 0; i < UART.Length; i++) {
if (values.Count == 0 || !values.Last.Value.Value.Equals (UART [i])) {
values.AddLast (new BitSet (UART [i], i));
}
values.Last.Value.Increment ();
}
// if baud is AUTO, then try to determine the baud rate based on shortest bit
if (baud == BAUD_AUTO) {
bitLength = Double.MaxValue;
for (LinkedListNode<BitSet> node = values.First.Next; node != values.Last; node = node.Next) {
bitLength = Math.Min (bitLength, node.Value.Count * samplePeriod);
}
}
int samplesPerBit = (int)(bitLength / samplePeriod);
DecoderOutput frameStartDecoderOutput = null;
bool frameStarted = false;
bool[] decodedBits = new bool[8]{ false, false, false, false, false, false, false, false };
int decodedBitsCount = 0;
int dataStartIndex = 0;
int dataStopIndex = 0;
DecoderOutput parityDecoderOutput = null;
bool parityBitFound = false;
// decode bytes
foreach (BitSet value in values) {
int bits = (int)Math.Round ((double)value.Count / samplesPerBit, MidpointRounding.ToEven);
if (!frameStarted) {
// check for start bit
if (!value.Value) {
if (bits > 0) {
frameStarted = true;
frameStartDecoderOutput = new DecoderOutputEvent(value.StartIndex, value.StartIndex + samplesPerBit,
DecoderOutputColor.Orange, "B");
}
// decode data if available
if (bits - 1 > 0) {
dataStartIndex = dataStopIndex = value.StartIndex + samplesPerBit;
for (int i = 0; i < bits - 1 && i < numberOfBits - 1; i++) {
decodedBits [i] = value.Value;
decodedBitsCount = i + 1;
}
}
}
} else {
// decode data
int processedBitCount = 0;
if (decodedBitsCount + bits <= numberOfBits) {
if (decodedBitsCount == 0) {
dataStartIndex = dataStopIndex = value.StartIndex;
}
for (int i = decodedBitsCount; i < decodedBitsCount + bits; i++) {
decodedBits [i] = value.Value;
processedBitCount++;
}
decodedBitsCount += processedBitCount;
dataStopIndex += processedBitCount * samplesPerBit;
} else if (decodedBitsCount + bits > numberOfBits) {
// decode remaining data if available
for (int i = decodedBitsCount; i < numberOfBits; i++) {
decodedBits [i] = value.Value;
processedBitCount++;
}
decodedBitsCount += processedBitCount;
dataStopIndex += processedBitCount * samplesPerBit;
// omit parity check if set to NONE
if (parityType == PARITY_NONE) {
parityBitFound = true;
}
// check parity
if (!parityBitFound && bits - processedBitCount > 0) {
bool parity = checkParity (decodedBits);
if ((parityType == PARITY_EVEN && value.Value == parity) ||
(parityType == PARITY_ODD && value.Value == !parity)) {
parityBitFound = true;
parityDecoderOutput = new DecoderOutputEvent (
value.StartIndex + processedBitCount * samplesPerBit,
value.StartIndex + (processedBitCount + 1) * samplesPerBit,
DecoderOutputColor.Green, "P");
processedBitCount++;
} else {
// if parity is wrong, then clear context values and proceed to next bit set
frameStarted = false;
frameStartDecoderOutput = null;
parityBitFound = false;
parityDecoderOutput = null;
decodedBitsCount = 0;
decodedBits = new bool[8]{ false, false, false, false, false, false, false, false };
continue;
}
}
// check for stop bits
if (parityBitFound && bits - processedBitCount > 0) {
if (value.Value == true && bits - processedBitCount >= numberOfStopBits) {
byte decodedByte = decodeByte (decodedBits);
decoderOutputList.Add (frameStartDecoderOutput);
decoderOutputList.Add (new DecoderOutputValue<byte> (dataStartIndex, dataStopIndex,
DecoderOutputColor.DarkBlue, decodedByte, "data"));
if (parityDecoderOutput != null) {
decoderOutputList.Add (parityDecoderOutput);
}
decoderOutputList.Add (new DecoderOutputEvent (
value.StartIndex + processedBitCount * samplesPerBit,
value.StartIndex + (processedBitCount + numberOfStopBits) * samplesPerBit,
DecoderOutputColor.Red, "E"));
}
// clear context values and proceed to next bit set
frameStarted = false;
frameStartDecoderOutput = null;
parityBitFound = false;
parityDecoderOutput = null;
decodedBitsCount = 0;
decodedBits = new bool[8]{ false, false, false, false, false, false, false, false };
continue;
}
}
}
}
}
return decoderOutputList.ToArray();
}
// decodes byte from bool array
private static byte decodeByte(bool[] bits) {
byte decodedByte = 0x00;
for (byte i = 0; i < 8; i++) {
if (bits [i]) {
decodedByte = (byte)(decodedByte | 0x01 << i);
}
}
return decodedByte;
}
// checks even parity, negate for odd parity
private static bool checkParity(bool[] bits) {
int ones = 0;
for (byte i = 0; i < 8; i++) {
if (bits[i]) ones++;
}
return ones % 2 != 0;
}
}
}