DF1 protocol problems

[saucekorn69 0]

Hi everyone, I'm currently writting a driver in order to communicate with a AB Micrologix 1500 following DF1 Protocol under vb.net. I succesfully implemented read and write with 3 adress fields, but It seems not working properly when I send unlimited number of commands. After a couple of commands, PLC only reponds NAK signal, like if the sink message is full. I tried to increase inteval time between command transfer, but it still doesn't work. Here is a part of my code: Do Try m_oRS232.Write(m_OutputBuffer) ' Send Command m_oRS232.Read(2) ' Read Response Catch ex As Exception Throw New CDF1Exception("Error 1 SEND COMMAND Function : ", ex) SendCommandV4 = False Exit Function End Try If m_InputBuffer(0) = DLE And m_InputBuffer(1) = ACK Then ' Message received correctly ' Read entire packet Exit Do ElseIf m_InputBuffer(0) = DLE And m_InputBuffer(1) = NAK Then ' Message not received correctly m_NAKCounter += 1 PurgeInputBuffer() ElseIf m_InputBuffer(0) = DLE And m_InputBuffer(1) = ENQ Then ' Message not received correctly m_ENQCounter += 1 PurgeInputBuffer() If m_ENQCounter = 0 Then Try m_oRS232.Write(Chr(DLE) + Chr(ACK)) PurgeInputBuffer() Catch ex As Exception Throw New CDF1Exception("Error 4 SEND COMMAND Function : ", ex) SendCommandV4 = False Exit Function End Try End If End If If m_NAKCounter >= 3 Or m_ENQCounter >= 3 Then Throw New CDF1Exception("Error 5, NAK counter: " + m_NAKCounter + " ENQ counter: " + m_ENQCounter) m_NAKCounter = 0 m_ENQCounter = 0 SendCommandV4 = False Exit Function End If Loop Try m_oRS232.Read(m_ReponseLength) Catch ex As Exception Throw New CDF1Exception("Error 2 SEND COMMAND Function : ", ex) SendCommandV4 = False Exit Function End Try If Buffer.ValidateNextMessage(m_oRS232.InputStream) Then Try m_oRS232.Read(2) m_InputBuffer = m_oRS232.InputStream Catch ex As Exception Throw New CDF1Exception("Error 3 SEND COMMAND Function : ", ex) SendCommandV4 = False Exit Function End Try If m_InputBuffer(0) = DLE And m_InputBuffer(1) = ENQ Then ' Validation correct m_InputBuffer(0) = DLE m_InputBuffer(1) = ACK SendCommandV4 = True Else m_NAKCounter += 1 End If Else ' Validation incorrect, re-send entire message m_InputBuffer(0) = DLE m_InputBuffer(1) = ENQ End If Try m_oRS232.Write(m_InputBuffer) PurgeInputBuffer() Catch ex As Exception Throw New CDF1Exception("Error 4 SEND COMMAND Function : ", ex) SendCommandV4 = False Exit Function End Try Does anyone have a advice or suggestions ?? Best regards. Nicolas Chaillou. Edited 11 Jul 2005 by saucekorn69

[saucekorn69 0]

Ok, I'm replying to myself, maybe someone will be able to give me an advice. My problem is that ReadPollRate value is not enough big, but according to Jiri Toman, I have to calculate it using baud rate value and numbers of integers I'm about to read. Fact is that i know my baudrate (19200) but I want to read an undetermined number of integers, so I'm kind of stuck... Can anyone help me ? Nicolas Chaillou.

[chas183 0]

This may be of some help. It is a very good read if nothing else. chas183 click here

[saucekorn69 0]

Thanks, but I already read this topic which as you said, really helped me. My driver perform all this kind of command described there, but I'm still stuck on timeouts problems...