How to auto open usb port after restart?

[Tomlee]

Hi

I am testing <InstallFolder>\examples\peripheral\usbd_cdc_acm project,   when I use serial tool of pc to open port, it can send or receive data.

but if I don't want to use serial tool of pc,   I  use app_usbd_cdc_acm_write() to send data out directly after restart,  and it runs here 

if (!dtr_state)
{
/*Port is not opened*/
return NRF_ERROR_INVALID_STATE;
}

, it shows port not opened.   Could somebody help me , please?

[Jørgen Holmefjord]

Hi,

When you say "directy after restart", which restart are you referring to then? Did you reset the nRF52833, the PC with the serial tool, the serial tool itself, etc?

Have you modified the example to call app_usbd_cdc_acm_write() somewhere else in the code? 

You should be able to use the APP_USBD_CDC_ACM_USER_EVT_PORT_OPEN/APP_USBD_CDC_ACM_USER_EVT_PORT_CLOSE events in the event handler to determine when the port is open and ready to send data.

Best regards,
Jørgen

[Jørgen Holmefjord]

Something needs to open the COM port on the other side of the USB connection for the event to be generated. 

Why would you want the want the code to generate the port open event if nothing have opened the port and can receive what you are writing?

[Tomlee]

Because I want to send some data when fw init.

Thank you.