AnsweredAssumed Answered

problem with usb device cdc in hal library

Question asked by ctc.ctc on Sep 26, 2017
Latest reply on Sep 27, 2017 by ctc.ctc

Hello, all

I recently learn to use stm32 usb device

I think it's easy to build a CDC example with HAL library in CubeMX,

And I put the code into stm32f429-discvoery, it's the HS pin, but actually use FS speed

I'm successfully to connect stm32 in Linux, like I use command "cat /dev/ttyACM0"

and I can easy to observe stm32 usb transmit data

 

But there is something strange and I don't know why.

When I plug the usb line and I can find /dev/ttyACM0,

I cannot direct connect it, like "cat /dev/ttyACM0"

it will show a error info "cat: /dev/ttyACM0: Device or resource busy"

 

But after about 10 seconds, it will success connect it.

Everytime I try same way, it all need 10 seconds wait,

All I setting in CubeMX for USB is default, only VBUS sensing with Enable

I'm not sure why, but it's there any possible to connect usb cdc more quickly?

Outcomes