CODEWITHSUNDEEP
c#serial-port
AndreB
AndreB

Reputation: 188

c# Handling handshake RTS/CTS

So just a bit of context I have 2 devices that communicate with each other by rs232 with RTS/CTS and i need to replace one of the devices with my own device and software.

I am trying to achieve this by using the System.IO.Ports.SerialPort library that from what i could gather online this library handles the handshaking by itself if we set the RtsEnable property to "true" and the Handshake property to "RequestToSend" but I am facing some issues receiving data from the device.

When testing my software i am not being able to receive anything from the device but if I change the wiring to simply work as a sniffer between the two original devices I can receive the data properly. From what I can gather it must be something I am doing wrong to handle the handshaking.

Here is the code i am trying:

stationPort = new SerialPort(stationPortNumber, baudRate, parity, dataBits, stopBits);
stationPort.RtsEnable = true;
stationPort.Handshake = Handshake.RequestToSend;
stationPort.DataReceived += StationPort_DataReceived;
stationPort.Open();

private static void StationPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    byte[] bytes = new byte[20];
    stationPort.Read(bytes, 0, stationPort.BytesToRead);
    string hexConvert = BitConverter.ToString(bytes);
    Console.WriteLine("Station OUT >>> " + hexConvert);
}

I also double checked the wiring to make sure it was properly connected and also changed the converter because sometimes these are not wired properly so I chose a MOXA UPort 1150 which is more reliable.

With that being said, my question is what am I doing wrong with my implementation? Am I supposed to do more to guarantee the handshaking?

Upvotes: 0

Views: 3404

Answers (1)

kunif
kunif

Reputation: 4350

Possibly, The equipment you are using may be half-duplex.

In that case, in order to communicate with the SerialPort class of C#, it is necessary to set Handshake to None and control the ON/OFF of the RTS signal by the application program itself.
The SerialPort class API does not have that function.
Handshake Enum

When using the communication function of Win32API, communication may be possible by setting the fRtsControl flag to RTS_CONTROL_TOGGLE in DCB.
DCB structure

RTS_CONTROL_TOGGLE 0x03
Specifies that the RTS line will be high if bytes are available for transmission. After all buffered bytes have been sent, the RTS line will be low.

In any case, you will need to check the communication specifications of the device.
However, even if you are not sure, it may be better to try the above control a little in C#.

You may also want to try @baddack's comment.
As noted, the fact that the DTR signal (DSR for the other party) is ON may be the basis for determining that communication is possible.

In connection with that, are the signal lines cross-connected?

Are TxD/RxD, RTS/CTS, DTR/DSR cross-connected to each other?
Also check what you need to do with these specifications for your equipment.

Upvotes: 1

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