HalfduplexUSB-to-serialbridgeusingtheST72611USB.PDFVIP

AN1071 APPLICATION NOTE HALF DUPLEX USB-TO-SERIAL BRIDGE USING THE ST72611 USB MICROCONTROLLER by USB Application Team INTRODUCTION This application note describes how to develop a bridge that allows a RS232 peripheral to be connected to a host computer through a USB connection. Communication with the host computer is based on the HID (Human Interface Device) USB protocol, permitting a maximum speed of 800 Bytes/sec with a USB Low Speed device. It makes development of the user host application easy by using the native HID driver and func- tions library provided by the OS (Operating System). A reference firmware has been developed by STMicroelectronics based on a low-cost, low- pin-count USB microcontroller such as the ST72611 or ST72623. It can be obtained by con- sulting your ST sales office. A demonstration board has also been developed: It can be obtained by consulting your ST sales office, and the schematic is given in this document. AN1071/0102 1/17 1 Table of Contents INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 SYSTEM FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 USB COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 SERIAL COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3