Maybe he's having the same issue we are, where we can't figure out how to get reliable USB communication working with the KR203? We're opening the device directly from the SetupAPI and CreateFile. That seems to be fine, and so does sending commands to the device. Reading from the device is the problem; many times, there is no response. We're trying to monitor status, and it's not going well.
You're toolbox app works much better, responding exactly half the time. How is your toolbox app opening, writing and reading the device? Is there sample code? Personally, I've spent almost a week on this issue with no success!!

Hi Robersi,
Could you please give me more details about your task?What device are you going to use to print labels through the USB port?How do you want to send labels to print (using your own app or something else)?Which language do you want to use for labels (ZPL or ZBI)?
Alexander PalchikovSoftware Engineer, Kutir MobilityPosted on behalf of Zebra Technologies