Arduino stops sending/receiving data over Serialport after random time

Question

I got a C# WPF application wich communcates with my arduino uno over serial port. Everything works fine for 3 to 20 seconds then i can not send or receive anything from/to the arduino.

What im trying to archieve: Connected a arduino uno to an optical sensor of a mouse to read from its registers, now i want to process the data on my pc.

I tried using another arduino uno and also some other mouse optical sensor, wich did not change anything. Opening and closing the serialport after each communication did not work for me. I have seen a few questions here on stack exchange, i looked through everyone but they could not help me. Serial.flush() seems to be not working, or its some kind of overflow i cant figure out.

I would really appreciate it if someone could explain me what the root of this problem is.

For completeness, here is my C# code:

 public class SerialCommunication
 {
 public SerialPort serialPort = new SerialPort();
 public SerialCommunication()
 {
 string[] ports = SerialPort.GetPortNames();
 if (ports.Count() == 1)
 {
 MessageBox.Show("No serialport is available");
 return;
 }
 serialPort.PortName = ports[1];
 serialPort.BaudRate = 115200;
 serialPort.Parity = Parity.None;
 serialPort.DataBits = 8;
 serialPort.Handshake = Handshake.None;
 serialPort.StopBits = StopBits.One;
 serialPort.NewLine = "\r\n";
 serialPort.WriteTimeout = 2000;
 serialPort.ReadTimeout = -1;
 serialPort.Open();
 }
 }
public partial class MainWindow : Window
 {
 public static readonly object _lock = new object();
 private SerialCommunication serialCommunication = new SerialCommunication();
 public MainWindow()
 {
 InitializeComponent();
 GetWindow(this).KeyDown += HandelKeyDown;
 serialCommunication.serialPort.DataReceived += (sender, args) =>
 {
 string bufferstring = ((SerialPort)sender).ReadLine();
 OnMessageReceived(bufferstring);
 //serialCommunication.serialPort.DiscardOutBuffer();
 //serialCommunication.serialPort.DiscardInBuffer();
 //Thread.Sleep(3);
 //byte[] buffer = new byte[15];
 //((SerialPort)sender).Read(buffer, 0, buffer.Length);
 //string bufferstring = Encoding.UTF8.GetString(buffer);
 };
 serialCommunication.serialPort.WriteLine("OK");
 }
 private void OnMessageReceived(string message)
 {
 if (message.Length != 15 || message.Contains('O') || message.Contains('K') || message.Contains('\n') || message.Contains('\r'))
 {
 serialCommunication.serialPort.DiscardInBuffer();
 serialCommunication.serialPort.DiscardOutBuffer();
 serialCommunication.serialPort.WriteLine("OK");
 return;
 }
 //Format: "y: 0x%02X,x: 0x%02X"
 string x = message.Substring(3, 4);
 string y = message.Substring(11, 4);
 int offsetX = (Convert.ToInt32(x, 16) - 128);
 int offsetY = (Convert.ToInt32(y, 16) - 128);
 // the next three lines only visualize the received data but do not change it 
 MoveX(offsetX / 50);
 MoveY(offsetY / 50);
 ShowMessage(message);
 Thread.Sleep(2);
 serialCommunication.serialPort.WriteLine("OK");
 }
}

Foto of how the application and data it receives look like: On the right side is the data, at the top the current position

Here is my arduino code:

#include <Arduino.h>
// 5v
#define POWER 13
// Serial I/O
#define SDIO 11
// Serial clock
#define SCK 12
// Registers
#define DELTAY 0x02
#define DELTAX 0x03
#define serialInputBufferSize 16
char dataBuffer[serialInputBufferSize];
unsigned short inputBufferLength = 0;
bool sendPosition = true;
char tmp[16];
void InitMouse()
{
 digitalWrite(SCK, HIGH);
 delayMicroseconds(5);
 digitalWrite(SCK, LOW);
 delayMicroseconds(1);
 digitalWrite(SCK, HIGH);
 // Wait for the serial transaction timer to time out:
 delay(1000);
}
byte readRegister(byte addr)
{
 byte r = 0;
 // Set the dataline to output
 pinMode(SDIO, OUTPUT);
 for (int i = 7; i >= 0; i--)
 {
 digitalWrite(SCK, LOW);
 digitalWrite(SDIO, addr & (1 << i));
 digitalWrite(SCK, HIGH);
 }
 // Switch the dataline from output to input
 pinMode(SDIO, INPUT);
 // The datasheet mentions to wait at least 100 μsec
 // when switching from write to read operations.
 // This is needed for the chip to prepare the data
 delayMicroseconds(110);
 // Clock trough the register and read its data
 for (int i = 7; i >= 0; i--)
 {
 digitalWrite(SCK, LOW);
 digitalWrite(SCK, HIGH);
 r |= (digitalRead(SDIO) << i);
 }
 // Delay at the end guarantees >100 μsec before next transaction
 delayMicroseconds(110);
 return r;
}
byte y = 0;
byte x = 0;
void WaitForMovementThenSendPositionOffset()
{
 x = 0;
 y = 0;
 while (((y == 0 && x == 0) || x == NULL || y == NULL) && sendPosition)
 {
 delay(1); // kann eigentlich weg
 y = readRegister(DELTAY);
 x = readRegister(DELTAX);
 }
 if (sprintf(tmp, "y: 0x%02X,x: 0x%02X", y, x) > 0)
 {
 tmp[16] = 0;
 if (!Serial.println(tmp))
 {
 // Serial.end();
 // Serial.begin(9600);
 // Serial.begin(115200);
 Serial.flush();
 }
 sendPosition = false;
 }
}
void serialEvent()
{
 sendPosition = false;
 // Read serial data into the buffer
 while (Serial.available())
 {
 dataBuffer[inputBufferLength++] = Serial.read();
 }
 Serial.flush();
 if (strstr(dataBuffer, "OK"))
 {
 sendPosition = true;
 WaitForMovementThenSendPositionOffset();
 }
}
void setup()
{
 pinMode(SCK, OUTPUT);
 pinMode(SDIO, INPUT);
 pinMode(POWER, OUTPUT);
 digitalWrite(POWER, HIGH);
 Serial.setTimeout(1000);
 // Serial.begin(9600);
 Serial.begin(115200);
 InitMouse();
}
void loop()
{
}

• jsotola: what troubleshooting have you done?
• Michael Santos: @jsotola as mentioned above: I tried using another arduino uno and also some other mouse optical sensor, wich did not change anything. Opening and closing the serialport after each communication did not work for me. I have seen a few questions here on stack exchange, i looked through everyone but they could not help me. I also tried around with delay() and other useless stuff for 2 days now
• jsotola: start with basics ... lower the baud rate ... use a simple Arduino sketch that sends repeatedly "ABC123" one character at a time with a short pause in between characters ... observe the result on the C# side of the connection
• Michael Santos: @jsotola i tried baudrate 9600 wich did not help, on the c# side i get the results i want. I will add a foto of how my wpf application looks like and the data it receives, but thank you
• jsotola: you need to modify the arduino sketch to the minium code that still exhibits the undesired behavior ... that is why i said to start by sending ABC123 and see if it still happens

Answer 1

Every time you receives data, it tries to read a full line (SerialPort.ReadLine()). If there's not a full line available, it will block the current thread until there is or until it times out.

These calls will stack up and eventually cause the application to fail.

• Michael Santos: If i restart the c# application, it still does not work. I have to restart the arduino, then it works again. I think problem is on the arduino side, but i give it a try and use a buffer with SerialPort.Read() instead.

Answer 2

The problem was in the serialEvent() method. I did not rest the bufferindex where i red the received message so it allways stayed there until the arduino ran out of memory and also i did not gave the arduino enough time to receive the message so i added delay(1) there.

Here is my updated code:

void serialEvent()
{
 inputBufferLength = 0;
 sendPosition = false;
 delay(1);
 // Read serial data into the buffer
 while (Serial.available())
 {
 if (inputBufferLength < serialInputBufferSize)
 {
 dataBuffer[inputBufferLength++] = Serial.read();
 }
 else
 {
 Serial.read();
 }
 }
 Serial.flush();
 if (strstr(dataBuffer, "OK"))
 {
 sendPosition = true;
 WaitForMovementThenSendPositionOffset();
 }
}