DF1 for PLC5

Hi,

I am trying to communicate with PLC5 through VB.Net using DF1 protocol. To start with I am trying to get the plc to echo the data what I send. Here is the code that I am trying,

Dim DLE, STX, ETX, BCC As Byte
Dim DST, SRC As Byte
Dim TNSH, TNSL As Byte
Dim CMD, STS, FNC As Byte
Dim DATA As Byte
Dim R1, R2 As Byte

DLE = &H10
STX = &H2
DST = &H1
SRC = &H0
CMD = &H6
STS = &H0
TNSL = &H5
TNSH = &H0
FNC = &H0
DATA = &H64
ETX = &H3
BCC = &H9B

Dim TS() As Byte = {DLE, STX, DST, CMD, STS, TNSH, TNSL, FNC, DATA, ETX, BCC}

R1 = &H0
R2 = &H0

Dim RS() As Byte = {R1, R2}

Dim RS232 As New IO.Ports.SerialPort
RS232.PortName = "COM3"
RS232.BaudRate = 19200
RS232.DataBits = 8
RS232.StopBits = IO.Ports.StopBits.One
RS232.Parity = IO.Ports.Parity.None
If (RS232.IsOpen = False) Then
RS232.Open()
End If

RS232.Write(TS, 0, 10)

Threading.Thread.Sleep(500)

RS232.Read(RS, 0, 1)

RS232.Close()

MsgBox(RS(0).ToString)
MsgBox(RS(1).ToString)

I am trying to get the inital acknowledgement from the plc, but when the control comes to the read, it times out, without any reply.

I will appreciate if anybody who have experience with DF1 can help me out to find what I am doing wrong.

Thanks for the help in advance.

Regards.

Have you monitored the actual bytes that come out of the port ?

One thing that stands out is that the end-of-transmission should be two bytes: DLE ETX, instead of just ETX.

Thanks Eddie. It was my oversight. I corrected and tried that again. Now I get a NAK reply. Still, I am not sure whats wrong.

A few things:

If you goto sourceforge.net and search DF1, you'll find some example projects in both VB and C.

DF1 echo is CMD 0x0F FNC 0x05.

If you keep sending a message w/ the same TNS, depending on the receiving device's configuration it may ignore you.

Make sure you're configured for full duplex.

As Eddie mentioned, end of message is indeed DLE ETX.

Jason, I will check on the website you mentioned.

The DF1 manual says CMD 06 and FNC 00 for echo. (Page 7-8). I am not sure we are refering to the same command.

About the configuration for full duplex, is there anything to be addressed from the software side??

Sorry about the CMD/FNC, you are indeed correct. That's what I get for not paying attention to the section of the page that refers to the command I am interested in.

Have you checked to see if anything is coming back from the PLC, a DLE NAK, DLE ENQ, or DLE ACK?

Fix the ETX to DLE ETX?

Make sure your checksum(BCC or CRC) configuration matches what you are trying to do, BCC in this case.

Another note, DF1 defines multibyte value transmission as little endian, IOW least significant bytes are transmitted first. It looks like your TS array has the TNS bytes swapped. A minor issue, and won't be a problem at this stage in your program.

Yes i fixed up the ETX to DLE ETX, I also found the SRC missing in the transmission. I fixed that one too.

I am getting the DLE NAK reply from the PLC. Previously you mentioned about configuring for full duplex. Can you brief that please.

Ok, that's good. Have you made sure that your calculated BCC is correct?

Yes for simplicity, I have made the data to be &H0 and the BCC to be &H2. Still the reply is NAK.

The configuration for the PLC5 port is set for BCC?

Yes, its configured for the bcc.

Ok, can you post the exact bytes you are transmitting?

This is the latest

Dim DLE, STX, ETX, BCC As Byte
Dim DST, SRC As Byte
Dim TNSH, TNSL As Byte
Dim CMD, STS, FNC As Byte
Dim DATA As Byte
Dim R1, R2, R3 As Byte

DLE = &H10
STX = &H2
DST = &H0
SRC = &H0
CMD = &H6
STS = &H0
TNSL = &HB
TNSH = &H0
FNC = &H0
DATA = &H0 '&H64
ETX = &H3
BCC = &H2 '&H9B

Dim TS() As Byte = {DLE, STX, DST, SRC, CMD, STS, TNSH, TNSL, FNC, DATA, DLE, ETX, BCC}

R1 = &H0
R2 = &H0
R3 = &H0

Dim RS() As Byte = {R1, R2, R3}

Dim RS232 As New IO.Ports.SerialPort
RS232.PortName = "COM3"
RS232.BaudRate = 19200
RS232.DataBits = 8
RS232.StopBits = IO.Ports.StopBits.One
RS232.Parity = IO.Ports.Parity.None

If (RS232.IsOpen = False) Then
RS232.Open()
End If
RS232.DiscardInBuffer()

RS232.Write(TS, 0, 12)

Threading.Thread.Sleep(500)


RS232.Read(RS, 0, 2)

I am using the channel 0. I am wondering is it right to give both the source and desitination to be zero. Some of the examples I have seen in the web uses that. I even tried the 1 and 0 for source and destination and vice versa, but still no sucess. Is there any specific configuration made to the serial port to be in full duplex mode??

For full duplex, your PLC5 isn't going to care much about the SRC and DST values.

I don't know VB, but you show the BCC to be "&H2 '&H9B". What exactly does that mean? Is that two bytes? A BCC checksum is one byte.

The BCC shown is &H2 the other value following it is commented out.