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[N3] Serial loopback: second byte missing


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#1 Michiel

Michiel

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Posted 26 March 2016 - 11:06 PM

Hi all,

 

I'm doing some tests with my Netduino 3's UART ports, and I've come across something weird.

 

When doing a loopback on any serial port, the second byte that was written to the port, is missing from the bytes read back from that same (or other, doesn't matter) port.

 

Simplified code snippet:

namespace NetduinoApplication4
{
    public class Program
    {
        public static void Main()
        {
            var sp = new SerialPort(SerialPorts.COM1, 2400, Parity.None, 8, StopBits.One);
            sp.Open();

            var writeBuffer = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05 };
            var readBuffer = new byte[writeBuffer.Length];

            while (true)
            {
                sp.Write(writeBuffer, 0, writeBuffer.Length);
                sp.Flush();

                var read = sp.Read(readBuffer, 0, readBuffer.Length);

                Debug.Print("Read: " + readBuffer[0] + " " + readBuffer[1] + " " + readBuffer[2] + " " + readBuffer[3] + " " + readBuffer[4]);

                Thread.Sleep(1000);
            }
        }
    }
}

Output:

Read: 1 3 4 5 0
Read: 1 3 4 5 0
Read: 1 3 4 5 0

Of course, I'm expecting those lines to read "1 2 3 4 5". Also, the variable "read" is set to 4, instead of the expected 5.

 

I can reproduce this on every COM port and with different array sizes.

 

Netduino deploy tool output:

HalSystemInfo.halVersion:               4.3.1.0
HalSystemInfo.halVendorInfo:            Netduino 3 (v4.3.2.2) by Secret Labs LLC
HalSystemInfo.oemCode:                  34
HalSystemInfo.modelCode:                177
HalSystemInfo.skuCode:                  4103
HalSystemInfo.moduleSerialNumber:       00000000000000000000000000000000
HalSystemInfo.systemSerialNumber:       0000000000000000
ClrInfo.clrVersion:                     4.3.1.0
ClrInfo.clrVendorInfo:                  Netduino 3 (v4.3.2.2) by Secret Labs LLC
ClrInfo.targetFrameworkVersion:         4.3.1.0
SolutionReleaseInfo.solutionVersion:    4.3.2.2
SolutionReleaseInfo.solutionVendorInfo: Netduino 3 (v4.3.2.2) by Secret Labs LLC
SoftwareVersion.BuildDate:              Jul 14 2015
SoftwareVersion.CompilerVersion:        410894

Am I doing something wrong, or is this a bug?  :o






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