I have an Aruduino Mega and Duemilanove. I want each to communicate to each other. Can I have the Serial TX on the Mega send to the Serial RX on the Duemilanove?
I know that Serial.read will work on the Duemilanove to receive info from the Mega, but how do I send info from the Mega?
I would just use the Serial.print() function from the Mega.
I am not quite getting the outcome I was expecting. I think I might be using the print function incorrectly.
Mega code
int speedOfWheels;
int i = 0;
void setup() {
speedOfWheels = 0;
pinMode(0,INPUT);
pinMode(1,OUTPUT);
Serial.begin(9600);
Serial1.begin(9600);
}
void loop() {
Serial.print("doesn't matter");//send data to Duemilanove
if (Serial.available() > 0 && i == 0) {
speedOfWheels = Serial.read(); //get data from Duemilanove
Serial1.println(speedOfWheels);
}
i++;
}
Duemilanove code
#include <Wheel.h>
Wheel wheels;
void setup() {
pinMode(0,INPUT);
pinMode(1,OUTPUT);
Serial.begin(9600);
}
void loop() {
wheels.reverse(124);
delay(40);
if (Serial.available() > 0)//if data sent from Mega
Serial.write(wheels.getSpeed());//send data back to Mega
}
did you connect the grounds of the two boards together ?
You should !
No I didn't is that important?
Yes, it might not be the problem, but ground is the common reference for the RX and TX signals and they should be connected together.
Also in your duemielnove code you never read the data you just check if it is available, that way the buffer will not be emptied, and there will always be data if the mega sent data just once.
What's your project? Maybe we can make some suggestions that are more than just debugging, that would help you future-proof your journey.
Well I just wanted to see if I can get some communication between the two. I am just messing around mostly, trying to learn the capabilities of the arduino. I changed some of my code. I am just getting some weird symbols.
Duemilanove Code
#include <Wheel.h>
Wheel wheels;
char input[20];
void setup() {
// set all the other pins you're using as outputs:
pinMode(0,INPUT);
pinMode(1,OUTPUT);
Serial.begin(9600);
}
void loop() {
//turn led on to signal car is in operation
wheels.reverse(124);
delay(40);
int i = 0;
while (Serial.available() > 0) {
input[i] = Serial.read();
i++;
}
Serial.write(wheels.getSpeed());
}
Mega Code
int speedOfWheels;
void setup() {
speedOfWheels = 0;
pinMode(0,INPUT);
pinMode(1,OUTPUT);
Serial.begin(9600);
Serial1.begin(9600);
}
void loop() {
Serial.print("speed");
while (Serial.available() > 0) {
Serial1.println(Serial.read());
}
}
On the Mega
Serial is connected to the computer by default...
Serial1 is what you hook to the Nove
Which one is hooked to the computer and which is physically wired over to the Nove? Please describe pin/port numbers as well.
For the Nove:
Try using Serial.print(wheels.getSpeed(), HEX) and see if that changes things.
The Mega is going to be connected to the computer. I have Serial1 tx connected to the Nove rx and rx connected to tx.. I now get -1 as the out put.
With your last code, you are waiting, on both the Nove and the Mega, for the other one to send some data first.
In the Mega, I have Serial1.print(); at the first line. I thought this will send a message to the Nove. Than the Nove will pick it up with Serial.read()
Oops. Missed that.
Have you looked at the difference between Serial.print() and Serial.write()?
I still get -1. I know that the value sent from the Nove is not -1, it is 124
Ok, tell me if I'm getting warm.
Your Mega is hooked to the PC. Upon reset, it continuously prints "speedspeedspeedspeed" etc.. to your serial monitor.
You are trying to send a BYTE value from the PC to the Mega, which if the Mega receives the BYTE, it will transfer it to the Nove. Part of the problem may in fact be that you are sending the newline character to the Nove as well. Use Serial1.print( Serial.read() ); instead of the println version.
You are sending ASCII from the PC, so a space ' ' = 0x20 in HEX, and 'z' = 0x7A in HEX. It's kind of hard to type 0x00 through 0xFF when you are typing on your keyboard. I haven't found a reliable way to do it using ALT+DECIMAL VAL either, like ALT+248 for degree symbol '°'. You would eventually need to create a command sequence, or come up with a way to parse the data on the Nove, and send stuff like "SPD,00" through "SPD,FF" or "SPD,000" through "SPD,255".
Now on the Nove side, it's not clear what the input array is being used for, and you'll need to check the bounds on your index variable so you don't index off into LALA land in RAM.
Whatever index goes to though, supposedly to control wheel speed?, the Serial.write(wheels.getSpeed()); should be Serial.print(wheels.getSpeed(),HEX);
Then on the Mega side, instead of printing "speedspeedspeed" to the PC, how about:
while (Serial1.available() > 0) {
*Serial.print("Speed: "); *
Serial.println(Serial1.read(),DEC);
//Should look like
//Speed: 000
//Speed: 001
// ...
//Speed: 254
//Speed: 255
}
I was trying to send a value to the Nove, have the Nove get a value and return it to the Mega. The Serial1.print is to send the initial value to the Nove, not the serial monitor.
Serial is hardwired to PC
Serial1 is one of the OTHER UARTS that should be hooked to your Nove
Arduino Mega example:
// Arduino Mega using all four of its Serial ports
// (Serial, Serial1, Serial2, Serial3),
// with different baud rates:
void setup(){
Serial.begin(9600);
Serial1.begin(38400);
Serial2.begin(19200);
Serial3.begin(4800);
Serial.println("Hello Computer");
Serial1.println("Hello Serial 1");
Serial2.println("Hello Serial 2");
Serial3.println("Hello Serial 3");
}
void loop() {}
The Serial1 from the Mega is connected to the Nove.
Hopefully you have your Nove pins 0 and 1 hooked up to pins 18 and 19 of the Mega?