USB_CDC Port open notification automatically (DTR)

[SODIUM]

I use SDK 15.3.0 with the example of USB_CDC. In the example, the virtual com port transmission works only when the terminal sends a DTR signal. I need the DTR notification to be sent when the device is connected to the UBS. How can I send this signal from the program, for example, in the event APP_USBD_EVT_POWER_DETECTED? I know that there is an app_usbd_cdc_acm_ctx_t structure, but if you just write a positive number in line_state, nothing happens. Still need to call some kind of interrupt.

[Kenneth]

Check out this reply:

https://devzone.nordicsemi.com/f/nordic-q-a/10877/the-terminal-used-must-send-a-dtr-signal-in-order-to-configure-the-uart-interface-mcu-pins/40690#40690 

[SODIUM]

My desktop program works with a virtual COM port without sending a DTR signal. I can not change the program. I need to transfer data without sending a DTR signal.

[Kenneth]

What if you try to set .line_state = 1 as reset value in app_usbd_cdc_acm.c? 

static void cdc_acm_reset_port(app_usbd_class_inst_t const * p_inst)
{
    app_usbd_cdc_acm_t const * p_cdc_acm = cdc_acm_get(p_inst);
    app_usbd_cdc_acm_ctx_t *   p_cdc_acm_ctx = cdc_acm_ctx_get(p_cdc_acm);

    p_cdc_acm_ctx->line_state = 1;

    // Set rx transfers configuration to default state.
    p_cdc_acm_ctx->rx_transfer[0].p_buf = NULL;
    p_cdc_acm_ctx->rx_transfer[1].p_buf = NULL;
    p_cdc_acm_ctx->bytes_left = 0;
    p_cdc_acm_ctx->bytes_read = 0;
    p_cdc_acm_ctx->last_read  = 0;
    p_cdc_acm_ctx->cur_read   = 0;
    p_cdc_acm_ctx->p_copy_pos = p_cdc_acm_ctx->internal_rx_buf;
}

Edit: Looks like you have already tried this. Then it seems you don't have any other choice than to start for instance a terminal window prior to using your program to enable the DTR signal before starting your app.

Edit2: Looks like there are some threads on DTR signal already, e.g.:
https://social.technet.microsoft.com/Forums/en-US/ff955e67-9c9f-408a-b58f-c6d317ed1b08/windows-serial-port-dtr-handling-during-and-after-boot-stuck-high?forum=win10itprogeneral 

Have you for instance tried to point driver to nRF5_SDK_nnnn\examples\usb_drivers