Using circular buffer for reading data from serial port

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I am currently using an byte[] to store the response send by the serial port.

But the need is to store the data into an circular buffer (using the Circular Buffer provided on GitHub) and as data come into it

1.if data is not fully received discard it.
2.take some data
3.and parse it like E0 means start of data.

Basically the Circular buffer operation is what I am looking for?

What I have tried:

Here is the Circular buffer

using CircularBuffer;
using System;
using System.Collections.Generic;
using System.IO.Ports;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


namespace SerialPortCommunicationWithStateMachines
{
    public class DataReceiveHandle
    {
        public static int MAX_PACKET_LENGTH = ChannelDataCount.count;

        public bool newData = false;

        public int rxOffset = 0;

        public byte[] rxBuffer = new byte[MAX_PACKET_LENGTH];

      
        public byte[] rxPackage = new byte[MAX_PACKET_LENGTH];

     

        public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
        {
           // var xbuffer = new CircularBuffer<byte>(10);
            if (e.EventType != SerialData.Chars) return;

            SerialPort port = (SerialPort)sender;

            

            int bytesCount = port.BytesToRead;
          
            port.Read(rxBuffer, rxOffset, bytesCount);


            rxOffset = rxOffset + bytesCount;

            if (HasCompletePackage())
            {
                Console.WriteLine("Full packet has been received");
                rxBuffer.CopyTo(rxPackage, 0);
                rxOffset = 0;

                newData = true;
            }

            if (newData == true)
            {
                if (rxPackage[0] == 224
                    && rxPackage[1] == 242
                    && rxPackage[2] == 1
                    && rxPackage[3] == 0
                    && rxPackage[4] == 60
                    && rxPackage[5] == 37
                    && rxPackage[6] == 133
                    && rxPackage[7] == 0
                    && rxPackage[8] == 0)
                {
                    Console.WriteLine("Header Content is:");
                    for (int i = 0; i <= 8; i++)
                    {
                        Console.WriteLine(rxPackage[i]);
                    }
                }

                Console.WriteLine("Message Content is: ");

                for (int i = 9; i < MAX_PACKET_LENGTH; i++)
                {
                    Console.WriteLine(rxPackage[i]);
                }

            }


        }
        private bool HasCompletePackage()
        {
            if (rxOffset == 60)
                return true;
            else
                return false;
        }
    }
    }

Posted 4-Jun-18 19:53pm

Nishikant Tayade

Updated 7-Jun-18 22:44pm

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Comments

Mehdi Gholam 5-Jun-18 2:31am

And your question is?

Nishikant Tayade 5-Jun-18 2:36am

@MehdiGholam As there is no circular buffer implementation provided by default

How can i read the data send by serial port into Circular buffer(provided on Git) so to read it,parse it?

for details:
https://stackoverflow.com/questions/49593013/how-can-i-read-and-calculate-serial-port-with-circular-buffer-c-sharp

Nishikant Tayade 5-Jun-18 2:49am

@MehdiGholam can you please share an solution or another way out of this problem now?

Richard MacCutchan 5-Jun-18 3:06am

You need to Reply to the person you want to contact.

Patrice T 5-Jun-18 3:47am

To reply to a comment, use the 'Reply' button on left of user name (on top of comment).

Nishikant Tayade 5-Jun-18 4:17am

Ok.Can you please help me now?

Eric Lynch 5-Jun-18 8:40am

Looking at your attempted implementation, you are missing a few elements. With a circular buffer, one would expect your pointer rxOffset to proceed towards the end of the buffer (at buffer size) wrapping (or resetting) to the start. You seem to be missing logic to consider this case. Typically, a circular buffer would also have two pointers, which "chase" each other. One indicates where you next add data to the buffer and the other indicates where you next remove data from the buffer (aka read/write). You would also need to add logic to handle buffer overflow, mb making sure the write pointer doesn't overtake the read pointer. Finally, you probably need to handle a partial read at the buffer boundary (when a wrap occurs)...dividing your read into two parts. I have bad connectivity right now, or I'd include some sample code. I'd just Google it. It's a well-established, fairly simple pattern. There should be truckloads of samples / explanations available.

See: https://en.m.wikipedia.org/wiki/Circular_buffer
See also: http://geekswithblogs.net/blackrob/archive/2014/09/01/circular-buffer-in-c.aspx

Nishikant Tayade 8-Jun-18 1:33am

@EricLynch The solution that you have provided is completely right,in my serial port communication class I am using a new implementation of Ring Buffer provided on GitHub
https://github.com/xorxornop/RingBuffer/blob/master/PartiallyConcurrent/RingBuffer.cs

I don't know how many bytes of packet i will receive and that is the main issue that's why i am trying to use the Circular/Ring buffer,

public class DataReceiveHandle
{
public static int MAX_PACKET_LENGTH = ChannelDataCount.count;

public static bool newData = false;

public static int rxOffset = 0;
public static int rxWrite = 0;
public static int rxRead = 0;

public static byte[] rxBuffer = new byte[MAX_PACKET_LENGTH];

public static byte[] rxPackage = new byte[MAX_PACKET_LENGTH];

public static void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{

if (e.EventType != SerialData.Chars) return;

SerialPort port = (SerialPort)sender;

int bytesCount = port.BytesToRead;

port.Read(rxBuffer, rxOffset, bytesCount);

SequentialRingBuffer rBuffer = new SequentialRingBuffer(4096, rxBuffer, true);

rxWrite=rBuffer.CurrentLength;

// rxOffset = rxOffset + bytesCount;

byte[] tempArray = new byte[256];
tempArray=rBuffer.ToArray();

foreach (byte item in tempArray)
{
Console.WriteLine(item);
}

}
I tried different way but was unable to do an correct implementation, can you please have look at it?

[no name] 5-Jun-18 15:05pm

And the point of your "circular buffer" is ..... ?

I find plenty of "interesting" items at Princess Auto; though I don't always know what they are for either.

2 solutions

Solution 1

Quote:
there is no default implementation of circular/Ring Buffer in C#

And what do you think the Queue Class[^] is?

Quote:
This class implements a queue as a circular array. Objects stored in a Queue are inserted at one end and removed from the other.

Queues and stacks are useful when you need temporary storage for information; that is, when you might want to discard an element after retrieving its value. Use Queue if you need to access the information in the same order that it is stored in the collection ...

Posted 7-Jun-18 20:31pm

OriginalGriff

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Jochen Arndt · Accepted Answer · 2018-06-07T22:46:00

Note:
Answered this on a repost of this question but going to add it here as well because the repost might get deleted. Added also some more information.

I still don't think that there is a need for a ring buffer here.

You already have a buffer: rxBuffer. To make that a ring buffer all you have to do is handling the write access using rxOffset accordingly:

C#

// Check if we have to wrap to the begin of the buffer
int bytesToRead = min(bytesCount, rxBuffer.Length - rxOffset);
port.Read(rxBuffer, rxOffset, bytesToRead); 
rxOffset += bytesToRead;
if (rxOffset >= rxBuffer.Length)
{
    bytesToRead = bytesCount - bytesToRead;
    port.Read(rxBuffer, 0, bytesToRead); 
    rxOffset = bytesToRead;
}

Now you have a ring buffer. Depending on what to do with that you might implement a reader having another class level variable defining the current read position (and checking that rxOffset will not overrun that read position).

But implementing the above you might recognise that it does not solve your problem. Your problem is actually not how to implement a ring buffer but to define how the received data has to be handled (processed). That is a task which must be done before writing any line of code. Once you have defined that, you can think about possible implementations.

Assuming that you have a start sequence and a length field do this with each receiving:

Locate the start seqence if not detected so far
If start detected and enough following bytes has been received (length field present), get that
If length present, receive until all package bytes has been received
If a complete package data has been received, process the data

Note also that the above defines "states" as mentioned in an answer to your previous question.

If you think now about a possible implementation you might recognise that there is no need for a circular buffer. Using a "normal" buffer two times the size of the max. package length would be sufficient. All you need are class member variables (in bold because that is important here) for the current receive position (rxOffset), the start sequence position, the length, and optionally the state. Once a package has been received and processed, reset all those variable.