Serial Monitor Question

Projects Programming
1

I have an Arduino Mega communicating serially to this DMX controller:
http://response-box.com/gear/2010/04/rs-232-driven-dmx-engine/

In general, the unit works perfectly. I can send messages from a terminal emulator to this box all day and it works.

From the Arduino Serial Monitor, in the top field, I can type commands no problem, and it works perfectly.
For example: typing A321@255:000 in the top field tells the DMX controller to send value 255 to channel 321 with 000 ms delay. Works! "Both NL and CR" are checked off, and set to 9600.

However, when I try to send commands from within my code, such as:
Serial.println("A321@010:000");
It doesn't work!

Question:
What is the difference between typing in the top field of serial monitor, and embedding it in the code?

I should also mention I am have the TX and RX pins connected from the Arduino to a TTL to RS232 converter.

2

Typing in the serial monitor sends data to the rx pin on the arduino.
Printing from the arduino sends data from the TX pin.

3

Serial.println() sends CR and LF characters, which the DMX controller might not like. Try using Serial.print() instead.

4

AWOL:
Typing in the serial monitor sends data to the rx pin on the arduino.
Printing from the arduino sends data from the TX pin.

Hi Thanks for the response. I'm not sure I understand.
So when a message is sent from Serial Monitor, that message sent via the RX pin? That means that I just have to switch the RX and TX pins from the Arduino to my TTL/RS232 converter. Well, I just tried that, and guess what? It works! Thank you!

I don't really understand why. It would seem that sending a message should always go out the TX pin. It means that I have to swap those wires all the time from testing mode (manual sending of messages) and arduino mode (automated changes from the Arduino code).

But thank you for the insight. Could you explain a little about why this is the case. I'm really unclear on this.

5

christop:
Serial.println() sends CR and LF characters, which the DMX controller might not like. Try using Serial.print() instead.

6

anchan:
sending a message should always go out the TX pin

When the message comes from the SerialMonitor it is being received, not sent.

...R

7

I don't really understand why. It would seem that sending a message should always go out the TX pin.

It does.

The message goes out of the TX on your TTL/RS232 converter, which connects to RX on the Arduino.
When using Serial.print(), Arduino sends the message out of its TX to the RX on your TTL/RS232 converter.