/* Function for outputting usage info to the serial port.  */
static void help(void)
/* Function for outputting usage info to the serial port.  */
static void help(void)
{
    printf("Usage:\r\n");
    printf("a: Enter start channel for sweep/channel for constant carrier\r\n");
    printf("b: Enter end channel for sweep\r\n");
    printf("c: Start TX carrier\r\n");
    printf("d: Enter time on each channel (1ms-99ms)\r\n");
    printf("e: Cancel sweep/carrier\r\n");
    printf("m: Enter data rate\r\n");
    printf("o: Start modulated TX carrier\r\n");
    printf("p: Enter output power\r\n");
    printf("s: Print current delay, channels and so on\r\n");
    printf("r: Start RX sweep\r\n");
    printf("t: Start TX sweep\r\n");
    printf("x: Start RX carrier\r\n");
}