[En-Nut-Discussion] RS485 on NutOS

Hugo Simon hugo.simon at gmx.de
Tue Oct 23 20:37:10 CEST 2007

How can I use RS485 halfduplex on NutOS on Ethernut 2.1?

I set the RS485 setting as described in the turtorial and can receive
characters via

    fread(&buffer, 1, 1, RS485));

But I cannot send via

    fputc(((char *)packet)[i], RS485);

I initialized Uart as follows:

    u_long flow_485 = USART_MF_HALFDUPLEX;
     * Setup the uart1 device.
    NutRegisterDevice(&DEV_UART1, 0, 0);
    RS485 = fopen(DEV_UART1_NAME, "r+b");
    if (RS485==NULL)
        puts_P(PSTR("ERROR: cannot initialize RS485 interface"));
    _ioctl(_fileno(RS485), UART_SETSPEED, &baud);
    _ioctl(_fileno(RS485), UART_SETFLOWCONTROL, &flow_485);

If I send a character as shown, Simply nothing happens. Do I have to enable
the transmitter somehow?

I have some routines running on a naked AVR system without NutOS. Can I
implement them on NutOS, directly using the Uarts, Ports and Interrupts I
need or does that interfere with NutOS?
I think this would be a better solution, because my routines detect bus
collisions and other errors.

Any help would be nice

Thank you

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