Arduino and Raspberry Pi Serial communication + multiple variables

Question

I have a raspberry pi and an arduino. So far I have been able to have the Pi send data to the arduino using serial communication, however it only send one variable and I have multiple variables(2) that I want to send to the arduino (x,y coordinates). Does anyone know if this is possible. I want the first number that is sent from the pi to be the x and the second one the y and the next one the x of the next coord ect.

I have tried editing the code that I use to send one variable but it doesn't work.

Any help would be awesome

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Dead-coder Dead-coder · Accepted Answer · 2013-08-12T20:42:19

Consider the following method to send 2 variable at the same time:

    int xpos, ypos;

    char x_tx_buffer[20], y_tx_buffer[20];
    char x_dummy_buffer[20];
    char y_dummy_buffer[20];
    char *p_x_tx_buffer, *p_y_tx_buffer;

    sprintf(x_dummy_buffer,"%d", xposs);
    sprintf(y_dummy_buffer,"%d", yposs);

    p_x_tx_buffer = &x_tx_buffer[0];
    *p_x_tx_buffer++ = x_dummy_buffer[0];
    *p_x_tx_buffer++ = x_dummy_buffer[1];
    *p_x_tx_buffer++ = x_dummy_buffer[2];
    *p_x_tx_buffer++ = x_dummy_buffer[3];

    p_y_tx_buffer = &y_tx_buffer[0];
    *p_y_tx_buffer++ = y_dummy_buffer[0];
    *p_y_tx_buffer++ = y_dummy_buffer[1];
    *p_y_tx_buffer++ = y_dummy_buffer[2];
    *p_y_tx_buffer++ = y_dummy_buffer[3];
    uart0_filestream = open("/dev/ttyAMA0", O_RDWR | O_NOCTTY | O_NDELAY);      //Open in non blocking read/write mode
    if (uart0_filestream == -1)
    {
        //ERROR - CAN'T OPEN SERIAL PORT
        printf("Error - Unable to open UART.  Ensure it is not in use by another application\n");
    }
    if (uart0_filestream != -1)
    {
        int countx = write(uart0_filestream, &x_tx_buffer[0], (p_x_tx_buffer - &x_tx_buffer[0]));       //Filestream, bytes to write, number of bytes to write
        int county = write(uart0_filestream, &y_tx_buffer[0], (p_y_tx_buffer - &y_tx_buffer[0]));       //Filestream, bytes to write, number of bytes to write
        if (countx < 0 || county < 0)
        {
            printf("UART TX error\n");
        }
    }
    close(uart0_filestream);

You can send a max of 8 bytes at a time. Keep that in mind and with that you can modify the about code to send your x and y values in the same uart0_filestream.

Good luck.

Arduino and Raspberry Pi Serial communication + multiple variables

1 Answers