Develop Reference

Read response from device modbus C#

Good afternoon everyone. Faced a problem: it is necessary to read data from the devices using the modbus protocol. I can not understand how to get a response from the device.
So I call my function, but how do I get data from the device? Maybe someone can help.
P.S. Please, do not advise using ready-made libraries like nmodbus - with them I did everything, I want to try it myself. Thank you.
static void Main(string[] args)
{
var serial = new SerialPort("COM6", 19200);
serial.Handshake = Handshake.None;
serial.Parity = Parity.None;
serial.DataBits = 8;
serial.StopBits = StopBits.One;
serial.Open();
serial.Write(ReadHoldingRegister(2, 1024, 16), 0, 8);
serial.Close();
Console.ReadLine();
}
#region Function 3
public static byte[] ReadHoldingRegister(int id, int startAddress, int length)
{
byte[] data = new byte[8];
byte High, Low;
data[0] = Convert.ToByte(id);
data[1] = Convert.ToByte(3);
byte[] _adr = BitConverter.GetBytes(startAddress - 1);
data[2] = _adr[1];
data[3] = _adr[0];
byte[] _length = BitConverter.GetBytes(length);
data[4] = _length[1];
data[5] = _length[0];
myCRC(data, 6, out High, out Low);
data[6] = Low;
data[7] = High;
return data;
}
#endregion
#region CRC
public static void myCRC(byte[] message, int length, out byte CRCHigh, out byte CRCLow)
{
ushort CRCFull = 0xFFFF;
for (int i = 0; i < length; i++)
{
CRCFull = (ushort)(CRCFull ^ message[i]);
for (int j = 0; j < 8; j++)
{
if ((CRCFull & 0x0001) == 0)
CRCFull = (ushort)(CRCFull >> 1);
else
{
CRCFull = (ushort)((CRCFull >> 1) ^ 0xA001);
}
}
}
CRCHigh = (byte)((CRCFull >> 8) & 0xFF);
CRCLow = (byte)(CRCFull & 0xFF);
}
#endregion
}

Processing a response is not "simple", you really need to account for errors, inter character and inter packet timing, etc. It should also probably be on a separate high-priority thread. The Modbus specs have some processing state diagrams that illustrate what (at a minimum) should be done. However, as a VERY SIMPLE, brute force, polling EXAMPLE, you could start with something like this:
static Queue<byte> GetResponse(SerialPort serial, int timeoutMSecs)
{
Queue<byte> response = new Queue<byte>();
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
while (stopwatch.ElapsedMilliseconds < timeoutMSecs)
{
if (serial.BytesToRead == 0) continue; // Nothing received, continue waiting
response.Enqueue((byte)serial.ReadByte()); // Add rx byte to queue
stopwatch.Reset(); // Reset timeout
if (response.Count > 255) break; // Maximum RTU packet?
}
return response;
}
In your main function
static void Main(string[] args)
{
...
serial.DiscardInBuffer(); // Clear any remaining rx bytes
serial.Write(ReadHoldingRegister(2, 1024, 16), 0, 8);
Queue<byte> response = GetResponse(serial, 5);
if (response.Count > 0)
{
// Process Response
// 1) check the CRC
// 2) if crc ok, check if it is an exception response
// 3) if not an exception check that it "matches" the request
// ...
}
...
}

summing Int32 represented by byte array in c#

I have an array of audio data, which is a lot of Int32 numbers represented by array of bytes (each 4 byte element represents an Int32) and i want to do some manipulation on the data (for example, add 10 to each Int32).
I converted the bytes to Int32, do the manipulation and convert it back to bytes as in this example:
//byte[] buffer;
for (int i=0; i<buffer.Length; i+=4)
{
Int32 temp0 = BitConverter.ToInt32(buffer, i);
temp0 += 10;
byte[] temp1 = BitConverter.GetBytes(temp0);
for (int j=0;j<4;j++)
{
buffer[i + j] = temp1[j];
}
}
But I would like to know if there is a better way to do such manipulation.

You can check the .NET Reference Source for pointers (grin) on how to convert from/to big endian.
class intFromBigEndianByteArray {
public byte[] b;
public int this[int i] {
get {
i <<= 2; // i *= 4; // optional
return (int)b[i] << 24 | (int)b[i + 1] << 16 | (int)b[i + 2] << 8 | b[i + 3];
}
set {
i <<= 2; // i *= 4; // optional
b[i ] = (byte)(value >> 24);
b[i + 1] = (byte)(value >> 16);
b[i + 2] = (byte)(value >> 8);
b[i + 3] = (byte)value;
}
}
}
and sample use:
byte[] buffer = { 127, 255, 255, 255, 255, 255, 255, 255 };//big endian { int.MaxValue, -1 }
//bool check = BitConverter.IsLittleEndian; // true
//int test = BitConverter.ToInt32(buffer, 0); // -129 (incorrect because little endian)
var fakeIntBuffer = new intFromBigEndianByteArray() { b = buffer };
fakeIntBuffer[0] += 2; // { 128, 0, 0, 1 } = big endian int.MinValue - 1
fakeIntBuffer[1] += 2; // { 0, 0, 0, 1 } = big endian 1
Debug.Print(string.Join(", ", buffer)); // "128, 0, 0, 0, 1, 0, 0, 1"
For better performance you can look into parallel processing and SIMD instructions - Using SSE in C#
For even better performance, you can look into Utilizing the GPU with c#

How about the following approach:
struct My
{
public int Int;
}
var bytes = Enumerable.Range(0, 20).Select(n => (byte)(n + 240)).ToArray();
foreach (var b in bytes) Console.Write("{0,-4}", b);
// Pin the managed memory
GCHandle handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
for (int i = 0; i < bytes.Length; i += 4)
{
// Copy the data
My my = (My)Marshal.PtrToStructure<My>(handle.AddrOfPinnedObject() + i);
my.Int += 10;
// Copy back
Marshal.StructureToPtr(my, handle.AddrOfPinnedObject() + i, true);
}
// Unpin
handle.Free();
foreach (var b in bytes) Console.Write("{0,-4}", b);
I made it just for fun.
Not sure that's less ugly.
I don't know, will it be faster? Test it.

Calculate CRC 8 of data received on serial port c#

I am receiving data from serial port in an byte array
How can I calculate the checksum of the data not included the sync (54) and checksum (F2) byte and want to match with the last check sum byte.
Updated :
int bytes = comport.BytesToRead;
byte indexCRC;
int sumCRC = 0;
byte checksumCRC = 0;
byte checksum;
byte[] RXBuffer = new byte[bytes];
comport.Read(RXBuffer, 0, bytes);
checksum = RXBuffer.Last();
byte[] RXBufferCRC = new byte[bytes];
for (indexCRC = 1; indexCRC < RXBufferCRC.Length; indexCRC++)
{
sumCRC = sumCRC + RXBufferCRC[indexCRC];
}
checksumCRC = (byte)(sumCRC);

Start the index from 1 but before doing that delete the last index of the array and store the array in an other array something like that
int Secbytes = comport.BytesToRead;
byte[] SecRXBuffer = new byte[Secbytes];
Array.Copy(SecRXBuffer, VanguardConstants.RECEIVEINDEX, RXBuffer, 0, Secbytes);
byte[] tmp = new byte[bytes - 1];
Array.Copy(RXBuffer, tmp, Secbytes - 1);
for (i = 1; i < tmp.Length; i++)
{
Sum = (byte)(Sum + tmp[i]);
}
Checksum = ((byte)Sum);

http://err.se/crc8-for-ibutton-in-c/
Here is an implementation of a CRC8 function in C#.

Converting from byte[] to string

I have the following code:
using (BinaryReader br = new BinaryReader(
File.Open(FILE_PATH, FileMode.Open, FileAccess.ReadWrite)))
{
int pos = 0;
int length = (int) br.BaseStream.Length;
while (pos < length)
{
b[pos] = br.ReadByte();
pos++;
}
pos = 0;
while (pos < length)
{
Console.WriteLine(Convert.ToString(b[pos]));
pos++;
}
}
The FILE_PATH is a const string that contains the path to the binary file being read.
The binary file is a mixture of integers and characters.
The integers are 1 bytes each and each character is written to the file as 2 bytes.
For example, the file has the following data :
1HELLO HOW ARE YOU45YOU ARE LOOKING GREAT //and so on
Please note: Each integer is associated with the string of characters following it. So 1 is associated with "HELLO HOW ARE YOU" and 45 with "YOU ARE LOOKING GREAT" and so on.
Now the binary is written (I do not know why but I have to live with this) such that '1' will take only 1 byte while 'H' (and other characters) take 2 bytes each.
So here is what the file actually contains:
0100480045..and so on
Heres the breakdown:
01 is the first byte for the integer 1
0048 are the 2 bytes for 'H' (H is 48 in Hex)
0045 are the 2 bytes for 'E' (E = 0x45)
and so on..
I want my Console to print human readable format out of this file: That I want it to print "1 HELLO HOW ARE YOU" and then "45 YOU ARE LOOKING GREAT" and so on...
Is what I am doing correct? Is there an easier/efficient way?
My line Console.WriteLine(Convert.ToString(b[pos])); does nothing but prints the integer value and not the actual character I want. It is OK for integers in the file but then how do I read out characters?
Any help would be much appreciated.
Thanks

I think what you are looking for is Encoding.GetString.
Since your string data is composed of 2 byte characters, how you can get your string out is:
for (int i = 0; i < b.Length; i++)
{
byte curByte = b[i];
// Assuming that the first byte of a 2-byte character sequence will be 0
if (curByte != 0)
{
// This is a 1 byte number
Console.WriteLine(Convert.ToString(curByte));
}
else
{
// This is a 2 byte character. Print it out.
Console.WriteLine(Encoding.Unicode.GetString(b, i, 2));
// We consumed the next character as well, no need to deal with it
// in the next round of the loop.
i++;
}
}

You can use String System.Text.UnicodeEncoding.GetString() which takes a byte[] array and produces a string.
I found this link very useful
Note that this is not the same as just blindly copying the bytes from the byte[] array into a hunk of memory and calling it a string. The GetString() method must validate the bytes and forbid invalid surrogates, for example.

using (BinaryReader br = new BinaryReader(File.Open(FILE_PATH, FileMode.Open, FileAccess.ReadWrite)))
{
int length = (int)br.BaseStream.Length;
byte[] buffer = new byte[length * 2];
int bufferPosition = 0;
while (pos < length)
{
byte b = br.ReadByte();
if(b < 10)
{
buffer[bufferPosition] = 0;
buffer[bufferPosition + 1] = b + 0x30;
pos++;
}
else
{
buffer[bufferPosition] = b;
buffer[bufferPosition + 1] = br.ReadByte();
pos += 2;
}
bufferPosition += 2;
}
Console.WriteLine(System.Text.Encoding.Unicode.GetString(buffer, 0, bufferPosition));
}

number formation for byte conversion

How to format the number which can be converted to Byte[] (array);
I know how to convert the result value to byte[], but the problem is how to format the intermediate number.
This is by data,
int packet = 10;
int value = 20;
long data = 02; // This will take 3 bytes [Last 3 Bytes]
i need the long value, through that i can shift and I'll fill the byte array like this
Byte[0] = 10;
Byte[1] = 20;
Byte[2] = 00;
Byte[3] = 00;
Byte[4] = 02;
Byte 2,3,4 are data
but formatting the intermediate value is the problem. How to form this
Here is the sample
long data= 683990319104; ///I referred this as intermediate value.
This is the number i receiving from built in application.
Byte[] by = new byte[5];
for (int i = 0; i < 5; i++)
{
by[i] = (byte)(data & 0xFF);
data>>= 8;
}
Here
Byte[0] = 00;
Byte[1] = 00; //Byte 0,1,2 are Data (ie data = 0)
Byte[2] = 00;
Byte[3] = 65; //Byte 3 is value (ie Value = 65)
Byte[4] = 159; // Byte 4 is packet (is Packet = 159);
This is one sample.
Currently BitConverter.GetBytes(..) is ues to receive.
Byte while sending, the parameter is long.
So i want the format to generate the number 683990319104 from
packet = 159
value = 65
data = 0
I think now its in understandable format :)

Not entirely sure what you are asking exactly, but I think you are looking for BitConverter.GetBytes(data).

The use of 3 bytes to define the long seems unusual; if it is just the 3 bytes... why a long? why not an int?
For example (note I've had to make assumptions about your byte-trimming based on your example - you won't have the full int/long range...):
static void Main() {
int packet = 10;
int value = 20;
long data = 02;
byte[] buffer = new byte[5];
WritePacket(buffer, 0, packet, value, data);
for (int i = 0; i < buffer.Length; i++)
{
Console.Write(buffer[i].ToString("x2"));
}
Console.WriteLine();
ReadPacket(buffer, 0, out packet, out value, out data);
Console.WriteLine(packet);
Console.WriteLine(value);
Console.WriteLine(data);
}
static void WritePacket(byte[] buffer, int offset, int packet,
int value, long data)
{
// note I'm trimming as per the original question
buffer[offset++] = (byte)packet;
buffer[offset++] = (byte)value;
int tmp = (int)(data); // more efficient to work with int, and
// we're going to lose the MSB anyway...
buffer[offset++] = (byte)(tmp>>2);
buffer[offset++] = (byte)(tmp>>1);
buffer[offset] = (byte)(tmp);
}
static void ReadPacket(byte[] buffer, int offset, out int packet,
out int value, out long data)
{
// note I'm trimming as per the original question
packet = buffer[offset++];
value = buffer[offset++];
data = ((int)buffer[offset++] << 2)
| ((int)buffer[offset++] << 1)
| (int)buffer[offset];
}

oooh,
Its simple
int packet = 159
int value = 65
int data = 0
long address = packet;
address = address<<8;
address = address|value;
address = address<<24;
address = address|data;
now the value of address is 683990319104 and i termed this as intermediate value. Let me know the exact term.