Archive for October, 2011
The I2C interface is relatively uncomplicated to write for on the AVR, not withstanding all the details of the protocol and all the messages generated by the AVR hardware. The more advanced AVR microcontrollers, support the I2C two wire interface – three wires if counting ground. It is not called I2C in the Atmel documentation however. Instead …..
Example Three
Create a new example directory and set it up as before in example one. Next edit usbconfig.h and change the values to the following.
Set USB_CFG_HAVE_INTRIN_ENDPOINT to 1,
set USB_CFG_DEVICE_CLASS to 0,
set USB_CFG_INTERFACE_CLASS to 3,
set USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH to 34, and
set USB_CFG_IMPLEMENT_FN_WRITE to 1.
The source code for example three is given in the download.
The report descriptor now …..
The HID Interface
All HID interfaces are required to have one IN endpoint, besides the control endpoint zero. If there is no IN endpoint, a HID device will not be created on the host. This is so even if the HID interface does not send any input reports. At least this is how the Linux kernel behaves.
In …..
USB can be quite a complex interface to learn. It is definitely not as easy to explain or as intuitive as the well known serial port. The specification for USB is hundreds of pages long. Books such as USB Complete by Jan Axelson and USB Design by Example by John Hyde are just as big. There …..
