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RS485 Tracer with USB interface Disclosure Number: IPCOM000016236D
Original Publication Date: 2002-Nov-30
Included in the Prior Art Database: 2003-Jun-21

Publishing Venue



Disclosed is a tracer device for the RS485 communication line with the USB interface. A tracer is required to analysis data flow between host computer and I/O peripheral devices to debug interface problems. The RS485 is serial interface standard, however it is not so popular as the RS232 and the USB, so tracers for RS485 was expensive and not commercially available. The USB(Universal Serial Bus) is a popular interface between PC and I/O peripheral devices. Almost all PC have USB ports and Operating Systems, such as Windows, Linux, support USB recently. The USB keyboard protocol is defined strictly by the Human interface Device(HID) specifications. If trace data are converted to a usage Index defined in the USB HID specifications, trace data from USB port can be seen like as text input from keyboard. No special application is required to see trace data. Large scale of data can be recorded depending on PC memory and storage size. Furthermore, trace data can be seen real-time as keyboard input operation. Normally, other tracers should be started recording, and recorded data cannot be seen during recording until it is stopped recording. How to implement the tracer is as follows; Modify firmware and power cable for keyboard logic card which have both USB and RS485 interface to use both interface simultaneously Modify keyboard firmware to receive all data from RS485, covert it to USB HID usage index using scan code conversion logic and transmit USB HID usage index via USB interface