RTS and CTS are high when SerialPort.Handshake = Handshake.RequestToSend


Run the following minimal program. Measure RTS and CTS. Both are high but both should be low. RTS should only be high once the input buffer is approaching full, but no data has been sent or received in this minimal program.

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.NetduinoPlus;
using System.IO.Ports;

namespace NetduinoPlusApplication1
public class Program
    public static void Main()
        SerialPort s = new SerialPort("COM2");
        s.Handshake = Handshake.RequestToSend;
        Debug.Print("Check D7 and D8"); // Netduino+
        while (true)


Garrcomm wrote Oct 19, 2011 at 8:20 AM

I've reproduced it with:
SolutionReleaseInfo.solutionVendorInfo: Netduino (v4.2.0.0 RC3) by Secret Labs LLC
SoftwareVersion.BuildDate: Oct 16 2011
SoftwareVersion.CompilerVersion: 410713

And can confirm the issue.

Garrcomm wrote Oct 22, 2011 at 7:14 AM

Ps. this also seems to happen with 4.1, so it's an old bug :)

SolutionReleaseInfo.solutionVendorInfo: Netduino Plus by Secret Labs LLC
SoftwareVersion.BuildDate: Feb 14 2011

SporkInTucson wrote Dec 10, 2011 at 6:01 PM

It's disappointing to see that there's no movement on this. Does "Release: Unassigned" mean that it's not even on the development road-map? RTS/CTS is listed as a feature on your spec sheets (http://netduino.com/netduino/specs.htm). If there's no timeline for fixing this, maybe you should remove mention of RTS/CTS from the specs. The forums have several RTS/CTS discussions, none of which end with successful hardware flow control, so I'm assuming that RTS/CTS never ever worked.

Garrcomm wrote Dec 10, 2011 at 7:28 PM

Hi SporkInTucson,

I can assure you people are working on it and it's being researched as part of the 4.2 update. Please bare with us.

remotewizard wrote Mar 7, 2012 at 2:34 PM

It would be a great help to me as well; I'd like to use a GPRS shield that requires RTS/CTS to send binary data.

kurtnelle wrote Jan 11, 2014 at 2:52 AM

Has there been any update on this? Desperately need hardware flow control.