Serial Comm with Xbee on 3pi

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1

Hello everyone, I am new.

I recently bought a 3pi and I have the following problem:

I am using the code example serial1 in where I have added from another example a method that gives the voltage of the battery. The method follows:

void bat_test()
{
	int bat = read_battery_millivolts();

	print_long(bat); // This works prints on the screen
	print("mV"); // This line also works, it prints
	memcpy_P(send_buffer, bat, 10); // my problem is here
	serial_send(send_buffer, 10); // and here

	delay_ms(300);
}

In the serial1 example I have added the above method and I have also added a new case to the switch statement:

case 'b':
			bat_test();
			break;

Therefore, when I send from the laptop a b it calls the bat_test(). The communication works, when I send a b it prints on the 3pi LCD screen but it doesnot send me back a correct buffer on my laptops console.

If you ask me why I have placed the number 10 on the buffer I do not know I was trying randomly. I think that number represents the bytes of the buffer? Without being sure.
I want to know how can I send variables from the program space to the serial port?

I know it is something easy for most of you in here, but I cannot find it.

Thank you in advance, for all your replies!

2

Hello.

memcpy is used to copy the elements of one array to another, but bat is an integer, not an array. You need a way to create an ASCII string representation of the integer bat (e.g. 5321 needs to become {‘5’, ‘3’, ‘2’, ‘1’}). You could write the code to do this yourself, or you could include <stdio.h> and use sprintf():

#include <stdio.h>

...

  char str[10];  // make the array long enough to hold your string + terminator char (0)!

  char len = sprintf(str, "%d mV", bat);
  if (len > 0)
    serial_send(str, len);

...

Note that I haven’t actually tried this code, so please let me know if you have any trouble with it.

- Ben

3

It worked perfectly fine.
Thank you so much! :smiley: