I'm developing a USB host application using the Stellarisware drivers and the EK-LM3S3748 board.
I have a bar code scanner plugged into the HOST port, and I'm seeing random VBUS errors, even when the scanner is just sitting there and not activated. It's a low-power Motorola scanner and plays fine when plugged into my Windows box.
Power is supplied to the board via the USB debug port, I'm not sure if that's not able to source enough power to drive the whole affair, but the scanner will work flawlessly for a while, then *boom* more VBUS errors.
Is anyone aware of what might cause this kind of issue? I've looked through the docs and the errata and nothing seems germane to this problem.
All info appreciated!
..ed..
Hello Edward,
Have you measured the voltage on VBUS whe you get VBUS errors? If so, does it go below 4.75 V ? Make sure you do not short VBUS and D+.
What version of Stellarisware are you currently using 8555? ( This information is located at the bottom of the readme.txt in one of the example projects i.e. usb_dev_msc)
If it would be possible run the unmodified usb_dev_msc example and connect a flash drive to the USB host, does the flash drive enumerate?
Do you have other devices connected to the LM3S3748 board, or do you only have the scanner connected?
What is the peak current consumption for the Motorola scanner?
- Erick
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Sorry about the long delay, we had a few minor fires to put out.
Turns out that, if I power the board externally (either with a 5V power supply or a 5V-to-USB wall wart), the problem goes away. It's just too much to run off the PC USB port, apparently.
Thanks for the response, though!