nrf9160 DK serial send - recieve buffer

[Adev]

Hello guys,

I wan`t to make an project that send trough serial port a new image to flash my nrf9160.

By the moment I managed to send and recieve data but only on uart0.

So if someone could explain me a little more what is hapening and how can i fix next issues i`m stuck with:

1. When I send a buffer from my python script ( on COM port that coresponds to uart0) I recieve only byte by byte not the whole string at once.

2. When I send back and string to the same port my soft goes in a infinite loop that sends the same message.

3. When I try to use uart1 I see no activity on none of 3 COM ports that are assigned to the pc when I connect my board.

Here is the code I`m using for uart : 

in main() :

uart = device_get_binding("UART_0");
if (!uart)
{
printk("Herror\r\n"); // error happens.
}

uart_irq_callback_set(uart, uart_cb);
uart_irq_rx_enable(uart);
printk("UART loopback start!\n");

callback() : 

static void uart_cb(struct device *x)
{
uart_irq_update(x);
int data_length = 0;

if (uart_irq_rx_ready(x)) {
data_length = uart_fifo_read(x, uart_buf, sizeof(uart_buf));
uart_buf[data_length] = 0;
}

}

and function used to send over uart: 

void uart_sendCOM(struct device *x, u8_t *Cont)
{
u16_t len = strlen(Cont);
uart_fifo_fill(x, Cont,len );
uart_irq_tx_enable(x);
}

Thank you for help.

[Adev]

I tried another, more simple aproach : 

void uart_sendCOM(struct device *x)
{
   k_sleep(1000);
   uart_fifo_fill(x, "test\r", strlen("test\r"));

}

static void uart_cb(struct device *x)
{
      int data_length = 0;
     uart_irq_update(x);

if (uart_irq_rx_ready(x))
   {
       data_length = uart_fifo_read(x, &uart_buf[uart_buff_len], sizeof(uart_buf));
       uart_buff_len += data_length;
    }

 if (uart_buff_len == UART_BUFF_MAX_SIZE || uart_buf[uart_buff_len - 1] == '\n' || uart_buf[uart_buff_len - 1] == '\r')
   {
    uart_buff_len = 0;
    }
}

In main() I have :

uart = device_get_binding("UART_0");
if (!uart)
{
printk("Herror\r\n"); // error happens.
}

uart_irq_callback_set(uart, uart_cb);
uart_irq_rx_enable(uart);
printk("UART loopback start!\n");

The problem is that recieve works good, but send part is not working...