Labview serial communication with Arduino to actuate relays

[What_a_Wookiee]

 I've created the attached VI to communicate over comm port with an Arduino that I want to use to control a couple relays. The Arduino actuates the relays quickly when triggered through the Arduino IDE, but I haven't been able to get it to work with LabView without including at least 1.516 seconds of delay before the VISA Write subVI I'm using to dump an integer into the serial channel as a trigger. My first thought was increase the baud rate from 9600, but after trying a couple higher rates including 115200, I saw no change in behavior. Open to suggestions if anyone is willing to offer. My Arduino code is below. Thanks in advance.

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int Relay1 = 4;

int Relay2 = 2;

int incomingByte1;

void setup() {

  pinMode(13, OUTPUT);     //Set Pin13 as output

  digitalWrite(13, HIGH);  //Set Pin13 High

  pinMode(Relay1, OUTPUT); //Set Pin4 as output

  pinMode(Relay2, OUTPUT); //Set Pin2 as output

  Serial.begin(9600); //Start serial communication at 9600 baud

}

void loop() {

 if (Serial.available() > 0) {

  incomingByte1 = Serial.read();

  if (incomingByte1 == 50)  //Sets negative polarity to relays on 2 input

  {digitalWrite(Relay1, LOW);

  digitalWrite(Relay2, HIGH);

  Serial.println("DOWN");    //Negative polarity string to indicator

  }

  else if (incomingByte1 == 51)  //Sets positive polarity to relays on 3 input

  {digitalWrite(Relay1, HIGH);

  digitalWrite(Relay2, LOW);

  Serial.println("UP");    //Positive polarity string to indicator

  }

  else {Serial.println(incomingByte1);}  //Sends trigger byte to indicator in all other cases

  }

}

[santo_13]

If you just want to get it done, use the LabVIEW Hobbyist Toolkit Download - NI and control the Digital Output lines from LabVIEW.

[crossrulz]

1. You should not need to flush the buffer on either end of your transaction.

2. That delay really should not be needed. You might want to try making a proper loop with an Event Structure in it so you can interactively control the Boolean control and send the command when required. Initialize the serial port before the loop and close the resource after the loop.

[What_a_Wookiee]

I don't want to just "get it done".  I want to know what's causing the issue with my current iteration.

[What_a_Wookiee]

Not flushing the buffer on one or both sides did not change the behavior.  I started with no delay and the VI didn't work at all.  It only works when I add in the delay with minimum 1.516 s of delay time.  Anything less than that and it stops working.  I also had it with a while loop structure to begin with, but it did not affect the behavior with or without the loop.  I'm wanting to use that VI as a subVI for a larger program, so I don't really have need for a loop structure in there in the final version.