Objective Development Forums

AVR-USB works well with the ATMega16 and 32. However, the fuse bits differ from device to device. This means that you can't simply use fuse bit values from an example device for one of the bigger ATMegas.

You don't need two devices, a composite device with two HID functions should be sufficient. Please see the USB HID specification how to build a report descriptor for a composite device. Or have a look at the report descriptor of a combined keyboard/mouse device.

You don't need a higher clock rate to lift the 254 bytes limit. That's only an optimization to save code size since we can store the message size in a byte. However, increasing the message size won't buy you much. Currently, assuming that you do 254 byte transfers, the number of transactions is 1 x ...

OK, then this is probably the practical limit with the software driver. Maybe you get more with a different host operating system or driver, maybe not.

If anybody gets better results, please post them here!

Did you insert a 3.3 V regulator in the processor's supply or take other measures to reduce the voltage levels on D+ and D-? There are chipsets which accept 5 V levels on USB and others where the input comparator's common mode range is exceeded. These other chipsets don't accept 5 V levels. If you d...

I don't have figures at hand, but the driver can be much faster. As far as I remember, it gets close to the theoretical limit of low speed USB (which is MUCH less than the 1.5 Mbit low level transfer rate). For optimum performance, please use control transfers of at least 128 bytes in size. Although...

I've added another project to the projects page: USB-Servo demonstrates how servos (as they are used in remote controlled vehicles) can be controlled via USB. See http://www.obdev.at/products/avrusb/projects.html for details.

I have added a new project to http://www.obdev.at/products/avrusb/projects.html : An I2C bus interface.

There are many chips with I2C bus interface available especially sensors. If you want to build an USB based sensor, this is a cheap and simple solution.