Serial communication between two arduinos

I am working on a project and have an Arduino Duemiloanove keeping track of speed and i need to send that information to the Arduino Mega. Right now i am using a "Serial.print" on the Duemilonave and "Serial.read" on the Mega. im not shure if this is correct. Please help me!

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0 MDeGrauw over 14 years ago

Hi did you made sure that the ground connection between the two arduino boards is ok.
You need 3wires for serial connection when the arduino boards both have their own power supply.
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0 jerriclynsjohn over 13 years ago in reply to MDeGrauw

hey when u said that we have to use 3wires for serial communication if the arduinos are powered by itself, what did you mean. I mean i use only the TX and RX of both powered arduinos and communication ceases when i remove the USB's (i power them using standard powerconnector, barrel jack)
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0 phoenixcomm over 13 years ago in reply to jerriclynsjohn
what he meant was, that when anytime you need three (3) wires:
transmit(1) to receive(2)
receive(1) to transmit(2)
logic ground(1 and 2)
and of course speed and start and stop bits must match on both CPUs.

that should work but I have a question???
how does cpu2 or visa versa know when you started talking???
you need to start your sentence or packet with some sort of thing that lets other guy to start listening.
sort of like start bits..

please look at my blog protocols.

enjoy
Cris
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0 e14 Contributor over 13 years ago in reply to phoenixcomm

For the arduino you use an if statement to check if there is something to read:

if (Serial.available() > 0) {
incomingByte = Serial.read();
}

then you can reference "incomingByte" elsewhere in the code.
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0 jerriclynsjohn over 13 years ago in reply to phoenixcomm

what do you mean by the 3. logic ground (1 and 2) . I'm quiet a newbie in this arduino world. help me!
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0 e14 Contributor over 13 years ago in reply to jerriclynsjohn

There are a total of three wires between the two arduinos.

1) TX to RX     (transmit pin to recieve pin)
2) RX to TX     (recieve pin to transmit pin)
3) Ground to Ground     (Common ground between the two arduinos)
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0 e14 Contributor over 13 years ago in reply to jerriclynsjohn

There are a total of three wires between the two arduinos.

1) TX to RX     (transmit pin to recieve pin)
2) RX to TX     (recieve pin to transmit pin)
3) Ground to Ground     (Common ground between the two arduinos)
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