Sharp7. Invalid buffer passed to Send/Receive.

[jacken]

Hi there, I'm a newbie when it comes to programming in C# with VS2015. I use S7-1200, all actions related with compability ( full acces, put/get, unchecked optimized block) were performed. The connection with PLC was made succesfully but i can't use other functions like DBRead. I'm always getting the same error as in the topic. I've made a simple DB in my PLC with 8 integer variables. Here's my very simple code:

//-------------- Connection
            var client = new S7Client();
            int result = client.ConnectTo("192.168.0.1", 0, 0);
            if (result == 0)
            {
                Console.WriteLine("Connected to 192.168.0.1");
            }
            else
            {

               Console.WriteLine(result);
               Console.WriteLine(client.ErrorText(result));
               Console.ReadKey();
               return;
            }
            //-------------- Read DB5
            Console.WriteLine("\n---- Read DB 5");
            int test1, test2, test3, test4, test5, test6, test7, test8;
            byte [] db5Buffer = new byte[16];
            result=client.DBRead(5, 0, 16, db5Buffer) ;
            test1 = S7.GetIntAt(db5Buffer, 0);
            test2 = S7.GetIntAt(db5Buffer, 2);
            test3 = S7.GetIntAt(db5Buffer, 4);
            test4 = S7.GetIntAt(db5Buffer, 6);
            test5 = S7.GetIntAt(db5Buffer, 8);
            test6 = S7.GetIntAt(db5Buffer, 10);
            test7 = S7.GetIntAt(db5Buffer, 12);
            test8 = S7.GetIntAt(db5Buffer, 14);
            if (result != 0)
            {
                Console.WriteLine("Error: " + client.ErrorText(result));
            }
            Console.WriteLine("Test3: " + test3);
            Console.WriteLine("Test4: " + test4);

So the question is what size of my Buffer should be? In my opinion 8 integers equal 16 bytes so do you have any idea what's wrong with the buffer?
Regards,
jacken

[Davide Nardella]

Hi,
maybe the message is wrong :(
the issue is not related to your parameters but to the telegram received.

could you insert a brekpoint at line 2217 of Sharp7.cs ?

                SendPacket(PDU, Size_RD);
                if (_LastError == 0)
                {
                    Length = RecvIsoPacket();
                    if (_LastError == 0)      // <--Insert breakpoint here
                    {
                        if (Length<25)
                            _LastError = S7Consts.errIsoInvalidDataSize;
                        else

I need to know the value of Length.
And, if possible, the dump of PDU[] (only 100 bytes).

Which firmware has your CPU ?

Could you make the same test using ClientDemo.exe ? (you should download Snap7 package)

[jacken]

Hello again,
I had a short break so sorry for responding just now.
I inserted the breakpoint as you mentioned and the value of Length is equal 19. So that's why this condition (Length<25) is true. I analyzed the RecvIsoPacket() method but couldn't find any solution for my problem. CPU firmware: 4.1.3. I made the same test with ClientDemo but when tried to use Data read/write option there was the following response: "CLI:function refused by CPU (unknown reason)". I don't know if that's what you mentioned about PDU dump but i made a screenshot of PDU when i used the breakpoint. Every byte after position 27 is equal 0. Any suggestions?

[Davide Nardella]

Hi,
"Cli:CLI:function refused by CPU" is an error raised by S71200/1500 CPU when a client cannot access either due to "protocol not enabled" or DB optimized.

Did you read this (the S71200/1500 chapter) ?
http://snap7.sourceforge.net/snap7_client.html#target_compatibility

DB must not be optimized.
GET/PUT must be enabled.

After the modifications remember to download the configuration into the PLC.

I tested Sharp7 with a CPU whit the same firmware and works.

[jacken]

Omg, I didn't download the hardware configuration to my plc. That fixed my problems. Thank you

[Chtitmaxou]

I know that this post is very old.
But do you remember how you found a solution?
Because i have exactly the same problem.
Length is equal to 19, so i can't read anything...

Thank you

[muhammed kurt]

Hi,
I got rid of the same problem by applying what Davide Nardella suggested. In my case the error message was "Bad data size passed to send/recv buffer is invalid" and length was always 19. Follow instructions on the link http://snap7.sourceforge.net/snap7_client.html#target_compatibility if you have a S71200/1500 device.

HTH

[Chtitmaxou]

finalement j'ai du downgrader le firmware vers 1.8.2 (à partir du 1.8.3 ça ne marche pas)
Merci quand-même