tud_cdc_connected() or tud_cdc_line_state_cb() problem when unplug USB connector

[hathach]

Discussed in https://github.com/hathach/tinyusb/discussions/1185

^{Originally posted by mastupristi November 11, 2021} hi, I'm using tinyUsb 0.12.0, on i.MX RT1051. I'm successfully using the tud_cdc_line_state_cb() callback to be notified when on the PC I connect/disconnect to the ttyACM0 (on PC I use minicom). The scenario is: with the usb cable plugged in I run minicom and the tud_cdc_line_state_cb() is called with dtr=1. In the moment I quit minicom the tud_cdc_line_state_cb() is called with dtr=0. The problem arises if, with minicom running, i unplug the usb cable. In that case the tud_cdc_line_state_cb() is not called. But when I plug the cable back in it is called again with dtr=1. This makes it difficult if not impossible to code state machines take into account the connection state.

Is this behavior intentional? How can I be notified of the cable disconnection?

best regards Max