topic Re: Virtual comport cannot detect disconnect in LPC Microcontrollers

Virtual comport cannot detect disconnect

kensu — Mon, 12 Jun 2017 12:26:09 GMT

Hi , I use the VCOM sample project to make my debug message output from USB Virtual com port. It work.

My evaluation board is MCB1800, I use the "usbd_rom_cdc_vcom" sample project.

But I find if my PC terminal tool(ex: teraTerm) is close or disconnected. The firmware cannot detect it's already disconnect.

How to detect if the terminal is already disconnected in the firmware?

It seems there is no interrupt handler to process the connection is disconnected from PC(connected --> disconnected).

Thanks

Ken

Re: Virtual comport cannot detect disconnect

jeremyzhou — Tue, 13 Jun 2017 06:38:30 GMT

Hi Ken Su,

Thank you for your interest in NXP Semiconductor products and

the opportunity to serve you.

I wonder whether you can share or tell me the demo you use, then I can replicate the issue on my site.

I'm looking forward to your reply.

Have a great day,

TIC

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

Re: Virtual comport cannot detect disconnect

kensu — Wed, 14 Jun 2017 01:18:09 GMT

Hi, the demo is very simple.

In the Cdc_vcom.c code, there si vcom_write API.

I use this API to output debug message, and PC receive it with terminal tool.

Then I close the terminal, I hope the firmware can detect the terminal is closed.

But "pVcom->tx_flags & VCOM_TX_CONNECTED" always show it is connected.

This status can not update.

The only way to detect if the PC terminal is closed is that the busy status is keep. So that the firmware may know the terminal is closed?

Any better method?

Thanks

Ken