Understanding the protocol

English
1

Just started programming in c# to receive events from push buttons.
I tried to understand the bits with the protocol explanation. I got the most important, but some help will always be welcome.

Receive:
I pressed on button 3 on kit VMB8PB
This is what I received : :15:248:1:4:0:4:0:0:240:4:

  1. 15 : ?
  2. 248 : ?
  3. 1 : Address
  4. 4: ?
  5. 0 : ?
  6. 4 : ButtonPress ( 4 = button 3)
  7. 0 : BottonRelease (will be 4 if released)
  8. 0 : BottonLongPress (will be 4 if longpress)
  9. 240: ?
  10. 4:?

Send
I tried to get the name of the button (addres 01). ‘Push button name request’
Tried with the packet creator , but no idea what i’ve got to send
11 01 00 ?? EF 00 00 01 00
RTR?

Is it the same packet I have got to send via TCP/IP ?

Manu

2

You received COMMAND_PUSH_BUTTON_STATUS - Page 3 of the protocol for the VMBxPB.

The bytes indicate the following:
0x0F: Start of packet (STX)
0xF8: High priority + Rtr Off
0x01: Address
0x04: 4 Data bytes
0x00: Data byte [1] = COMMAND_PUSH_BUTTON_STATUS
0x04: Data byte [2] = Bitmask for Button Pressed (btn 3 is pressed 00000100)
0x00: Data byte [3] = Bitmask for Button Released (none)
0x00: Data byte [4] = Bitmask for Button LongPressed (none)
0xF0: Checksum (2’s complement starting from STX to data byte [3])
0x04: End of packet (ETX)

3

Example for COMMAND_PUSH_BUTTON_NAME_REQUEST - Page 6 of the protocol for the VMBxPB:

0x0F: Start of packet (STX)
0xFB: Low priority + Rtr Off
0x01: Address
0x02: 2 Data bytes
0xEF: Data byte [1] = COMMAND_PUSH_BUTTON_NAME_REQUEST
0x01: Data byte [2] = Request name for pushbutton 1 (00000001)
0x03: Checksum (2’s complement starting from STX to data byte [2])
0x04: End of packet (ETX)

4

hi , after searching a lot on the web, I almost get the protocol send packets working. The only one I don’t know: how to generate " 0xFB: Low priority + Rtr Off "
Pdf says : SID10 & SID9 : Priority (00:hightes… 11 : lowest priority)
is this ‘11’ binary or Hex? and do i just need to add 0x01 when RTR is true?
-> priority_rtr (in code)

can someone help me?

thxx
Manu

[code]public class VelbusProtocol
{
public static byte GetCheckSum(List _bytes)
{
int checksum = _bytes[0];
for (int i = 1; i < _bytes.Count - 1; i++)
{
checksum += _bytes*;
}
checksum &= 0xff;
checksum ^= 0xff;
byte checksumb = byte.Parse(checksum.ToString());
return checksumb;
}

    public static byte] GeneratePackage(byte address, byte] parameters, byte priority, bool rtr)
    {
        // how to calulate this one?
        byte priority_rtr = 0xFB;

        List<byte> _datas = new List<byte>();
        _datas.Add(0x0F);                                       // SOF
        _datas.Add(priority_rtr);                              // add priority 
        _datas.Add(address);                                   // address
        _datas.Add(byte.Parse(parameters.Length.ToString()));   // add params count
        for (int i = 0; i < parameters.Length; i++) { _datas.Add(parameters*); }; // add params
        _datas.Add(GetCheckSum(_datas));                        // add Checksum
        _datas.Add(0x04);                                       // EOF
        return _datas.ToArray();
    }



    public static string test()
    {
        // Set led 1 on of kit VMB8PB on address 01
        byte] package = VelbusProtocol.GeneratePackage(0x01, new byte] { 0xF6, 0x01 }, 0x00, false);


        string temp = "";
        for (int i = 0; i < package.Length; i++)
        {
            temp += package*.ToString("X2") + " ";
        }
        return temp;
        //returns  "0F FB 01 02 F6 01 FC 04 "
    }[/code]***
5

My mistake, the rtr flag is in the data size byte, not in the priority byte.

Recap:

  • is always FB or F8
  • if you want on then add 0x40 to the

Without rtr on:
0x0F: Start of packet (STX)
0xF8: High priority
0x01: Address
0x04: 4 Data bytes and rtr off
…

With rtr on:
0x0F: Start of packet (STX)
0xF8: High priority
0x01: Address
0x44: 4 Data bytes and rtr on
…

Sample code for Delphi

procedure TPacket.SetPriority(const Value: TPriority);
begin
  if Value = vpLow then
    FPackedData[1] := $FB
  else
    FPackedData[1] := $F8;
end;

function TPacket.GetRtr: Boolean;
begin
  Result := ((FPackedData[3] and $40) = $40);
end;

procedure TPacket.SetRtr(const Value: Boolean);
begin
  if Value then
    FPackedData[3] := FPackedData[3] or $40 { set flag }
  else
    FPackedData[3] := FPackedData[3] and $0F; { clear flag }
end;

So basically the low order-nibble is the number of data bytes. And the high-order nibble contains a flag for rtr.

6

Its almost working. Got some problems with sending a request. (VMB8PB)

This one works :
Module Status request : 0F FB 01 02 FA 01 F8 04

These doesnt work :
Module type request : "0F FB 01 40 F4 04 "
Button Name Request : "0F FB 01 02 EF B1 03 04 "
Read from memory : "0F FB 01 03 FD 00 00 F4 04 "

any idea? is it the parity byte?

another small question:
what is the baudrate of the serial bus?
110; 300; 600; 1200; 2400; 4800; 9600; 14400; 19200; 38400; 56000 …

Manu

7

Your checksums are probably incorrect. The checksum for the first packet (module type request) should be 0xB5.

unsigned char checksum(unsigned char*lpData, int nSize)
{
	unsigned char c = 0;
	int i = 0;
	
	for(; i<nSize; ++i)
		c += lpData*;
	
	return (-c);
}

Current baud rate is 38400.*

8

think i found it:

public static byte GetCheckSum(List<byte> _bytes)
        {
            int checksum = _bytes[0];
            for (int i = 1; i < _bytes.Count; i++)
            {
                checksum += _bytes*;
            }
            checksum &= 0xff;
            checksum ^= 0xff;
            checksum += 0x01;
            byte checksumb = byte.Parse(checksum.ToString());
            return checksumb;
        }

this must be a good c# function*

9

That looks good indeed :slight_smile: But you could take almost exactly the same code as in C. C# appears to handle data types in the same manner.

[code]
public static byte GetChecksum(List _bytes)
{
byte checksum = 0;
for (int i=0; i<_bytes.Count; i++)
checksum += _bytes*;

return (byte)(-checksum);

}
[/code]*