Control NIOS II program from "NIOS II Console" (without HAL functions)

Hello,

I'm trying to implement control of NIOS II program from nios ii console.

Here is snippet of code:

void sw_get_command(cmd_type *cmd) {
    alt_u8 btn;
    btn = (alt_u8) btn_read(BTN_BASE) & 0xf;    // read 4 pushbuttons
    if (btn != 0) {                                // a button pressed
        if (btn & 0x01)                           // button 0 pressed
            cmd->pause = cmd->pause ^ 1;            // toggle pause bit
        if (btn & 0x02)                           // button 1 pressed
            cmd->prd = pio_read(SWITCH_BASE) & 0x03ff;  // load new interval
        if (btn & 0x04)
        {
            alt_u8 rvalid = 0;
            alt_u32 data_reg = 0;
            do{
                data_reg = IORD(JTAG_UART_BASE, JUART_DATA_REG_OFT);
                rvalid = data_reg >> 15 & 0x01;
            } while (rvalid == 0);
            printf("data = %c\n", (char)data_reg & 0xff);
            printf("ravail = %d\n", (data_reg >> 16) & 0xffff);
        }
        btn_clear(BTN_BASE);
    }
}

The sw_get_command is called from while(1) loop.

If button 2 is pressed (condition btn & 0x04), user is invited to type some value in NIOS II Console.

The value can have multiple symbols.

I'm faced to problem how to read all symbols. Actually when I read a symbol (in the command data_reg = iord(jtag_uart_base, juart_data_reg_oft)), it seems that read fifo is erased.

Otherwise how to explain that after leaving the do-while loop, the value of ravail (number of characters remaining in the read fifo) is 0 (1st image - screenshot of NIOS II console).

Another question: after some "exercises" with button 2, the communication crashes and Eclipse becomes unavailable (2nd screenshot - fragment of Windows Task Manager screenshot).

Thanks in advance.

https://alteraforum.com/forum/attachment.php?attachmentid=13559&stc=1