USB connection trouble

Question

I am currently running a robotic's project using an Hokuyo (URG-04LX-UG01 - http://www.hokuyo-aut.jp/02sensor/07scanner/urg_04lx_ug01.html). This one is plugged to my computer using USB. Although it creates the port "/dev/ttyACM0" when I plug it, I can't connect to it using the associated library (serial connection error). Until here, nothing's strange, bugs or misprogramming happens but here is my problem : When I plug the hokuyo to an USB HUB, which is also plugged to my computer, I can connect to it and everything works perfectly.

My laptop is a samsung 900x3c running Linux Mint 15.

Do you know what an USB HUB changes in the USB communication ? Is there a link with my laptop ? (I used to face the same problem using an ARM-Based embedded computer) Is it possible to fix the issue without using any hardware solution ? If it's not, is there anything more compact than an USB HUB which could fix it ?

Thanks !

Answer 1

Is your USB-HUB powered from external power adapter? URG-04LX-UG01 seems to consume 2,5W/5V=0,5A. This is limit for USB. Laptop USB ports are not so powerful and if device consumes a little bit more than max, then they just cut the power.

Update

The device is USB 2.0 Full Speed. I've seen USB controller, that had problems with USB 1.0 or USB 2.0 devices. Hub presents itself as USB 2.0 High Speed and handles USB 2.0 Full Speed transparently for the Laptops USB controller. Do you have another Laptop/PC to check this?

Answer 2

I'm kind of late on my feedback for that issue, but better late then never so :

I've been able to determine that the whole issue came from my USB cable. Somehow there was an electrical issue in that cable and the computer-or the hokuyo- was not able to properly communicate through it. I think that the USB HUB was somehow able to correct theses electrical issues.

Anyway, problem solved !