Cant send serial data using USB to serial help..

I must be missing something very basic and hoping someone can help.

I have an arduino UNO hooked up and I wired a serial to USB adaptor to my computer. I did reverse TX and RX (even though both are on the same computer hooked up a common ground).

I can read data from the arduino in my terminal window (tried Terra Term, Putty and Arduino monitor) but I can not send. The terminals just wont take any input.

I also tried using a nano with the reset to ground to try a different source.

If I loop back I can send and receive input without issue, as soon as I hook up to arduino I can only receive.

I hooked up 2 Arduino and used an example script that simply sends the letter H and L to turn the LED of one Arduino off and on (that works fine). When I substitute the sending arduino with a direct serial connection I can no longer send anything to the receiving arduino.

In Short: I can always receive on the Serial adaptor Works fine in loop back Checked my port settings to make sure they match Tried with and without ground Swapped TX and RX multiple times

What am I missing?

Any hints or help would be appreciated.

Arduino scripts that works until I try to substitute with USB to serial: Arduino A (which I tried to replace with serial adaptor

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println('H');
  delay(1000);
  Serial.println('L');
  delay(1000);
}

Arduino B. Receiving Arduino Script:

const int ledPin = 13; 
int incomingByte;      

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  if (Serial.available() > 0) {
    incomingByte = Serial.read();
    if (incomingByte == 'H') {
      digitalWrite(ledPin, HIGH);
    }
    if (incomingByte == 'L') {
      digitalWrite(ledPin, LOW);
    }
  }

}

Arduino A is continually sending ‘H’ and ‘L’ every second.

You need to do the same from the Serial Monitor window since you the human would be replacing the Arduino A.

yeah I know what the code is doing and I posted it simply to to stop wasted posts of people asking for the code.

It's not relevant to the issue that no matter terminal or adaptor I'm using I can not send any data to the Arduino.

VagGuy: It's not relevant to the issue that no matter terminal or adaptor I'm using I can not send any data to the Arduino.

What is relevant is how you have these two Arduinos connected.

And from your writing, I have no idea how they are connected.

ieee488:
What is relevant is how you have these two Arduinos connected.

And from your writing, I have no idea how they are connected.

How the arduino connected is not relevant AT ALL. Since I said the two arduino can communicate without issue.

As I stated before the problem is trying to use a serial to USB to communicate instead of a 2nd arduino.

I also stated that I had the serial to USB connected to the TX and RX and GND. I also stated that I tried to reverse the TX and RX multiple times in case I had them the wrong way around.

The point of the two arduinos was that they do communicate and that USB serial adaptor doesn’t. wow…

Don’t mean to be rude but did you even read my question?

VagGuy: How the arduino connected is not relevant AT ALL. Since I said the two arduino can communicate without issue.

As I stated before the problem is trying to use a serial to USB to communicate instead of a 2nd arduino.

Post two diagrams - one showing the connections between the two Arduinos when the communication worked. And the other showing the connections with the USB device when the communication does not work.

AND post the two programs that go with the two diagrams.

...R

VagGuy: Don't mean to be rude but did you even read my question?

Don't mean to be rude, but ever heard the phrase "a picture is worth a 1000 words"? ? ?

Your words have been extremely unhelpful bordering on useless in explaining your situation. Don't mean to be rude. :roll_eyes: