Interconnectivity 1 Oct 98 Page 6
Implementing a USB-to-InfraRed Dongle
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Philips Semiconductors - Asia Product Innovation Centre
Visit http://www.flexiusb.com
TECHNICAL DESCRIPTION
GENERAL
This application note describes the implementation of
§ A USB-IR dongle; and
§ A USB compound hub with a USB-IR dongle device.
The main difference in the two designs lie in the USB Controller used. To implement a USB
device, the PDIUSBD11 (D11) general-purpose USB interface is selected. To implement a
compound hub with USB-IR functionality, you must use PDIUSBH11A (H11A) or PDIUSBH12
(H12). The device functionality is the same for all the designs, H11A provides 4 USB walk-up
ports and the H12 provides only 2 USB walk-up ports.
The firmware implementation for the USB-IR dongle on the microcontroller can be divided into
two parts. The microcontroller has to service the USB controller and at the same time decode and
encode the data for the IR front-end. The hub functionality adds another 2 Kbytes of code onto
the firmware.
The USB-IR dongle portion uses the D11/H11A/H12 as the USB interface for implementing HID
functionality. This includes Keyboard, Mouse and Gamepad functionality.
For the USB-IR device only, it enumerates as a multi-interface composite device. The individual
interfaces, each conforms to the HID Class definition, be it a HID Keyboard, a HID mouse or a
HID gamepad. The default HID device driver from Windows 98 is loaded. Thus, the whole
system may be implemented ready to ship without a need to develop your own device driver.
For the compound hub with the USB-IR device, the hub is first enumerated. The generic driver
for Windows 98 is loaded before it enumerates the embedded USB-IR device. The enumeration of
the USB-IR device follows the same procedure as explained in the previous paragraph.
The USB-IR device translates USB requests into IR signals conforming to the Philips Infrared
RCMM (1-way) and Infrared RCMM² (2-way) protocols. The RCMM protocol is proprietary; an
NDA would be required to obtain the protocol description. The contact person for the NDA is
listed under the Contacts section.