ST AN2405 Application note

AN2405

Application note

Migrating from RS232-only applications to

RS232/USB applications using Turbo Plus uPSD

Introduction

Most laptops and recent desktops do not have serial ports however many legacy applications still use RS232. The scope of this application note is to migrate such RS232 applications to RS232/USB applications using Turbo Plus uPSD. Since Turbo Plus uPSD has two UART ports, one of them is used for the USB-to-Serial Bridge connection. The scope is to implement an easy migration with minimal impact on legacy applications.

Product(s) -Obsolete

Product(s) Obsolete

July 2007

Rev 1

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Contents	AN2405

Contents

1	Migration description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		3
	1.1	Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
	1.2	Loading CDC class drivers for USB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	3
	1.3	.INF file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	4

1.3.1 Usbser.inf (Windows 2000,XP only) file: . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.4 CDC Firmware Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5 CDC Class Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.6USB_UART1 Bridge (HW Connection-User setup or Automatic USB Detect) 8

		1.7 USB-to-Serial Bridge plug-in . . . . . . . . . . . . . .		Product(s). . . . . . . . . . . . . . . . . . . .	. 9
					9
		1.8 Example of easy migration to RS232_USB application: . . . . . . . . . . . . . .
	2	Conclusion . . . . . . . . . . .	. . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . . . . . .	10
	3	References . . . . . . . . . . . .	. .Obsolete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		11
	4	Revision history			12
			. . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . . . . . .
			-
		Product(s)
	Obsolete

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AN2405	Migration description

1 Migration description

1.1Architecture

									USB Migrated PC Application
									(Legacy Serial Port or Virtual
									Serial Port over USB)
		Legacy PC Application
									UARTdrivers + CDC class
									device drivers for USB
		UART drivers							(usbser.sys, usbser.inf)
									UARTT H/W & DB9 Connector
		UART H/W & DB9
									+
		Connector
									USB H/W & USB Type A
						Easy
									Product(s)
			RS232			Migration			Connector
		UART0 H/W & DB9								RS232 or USB
		Connector
									UART0 H/W & DB9
		UART0 firmware driver
									Connector
									+
						Obsolete CDC class driver
		Receiving over UART0
		UART0 only							USB H/W & USB Type B
		microcontroller							Connector
		Firmware Application
									UQRT0 firmware driver + USB
		Transmitting and
		Product(s)			-
									MCU -> Turbo Plus uPSD
									UART0 Tx and Rx connected
									to UART1 Rx and Tx
									(HW connection-User Setup or
									Automatic USB Detect)
Obsolete									USB-to-UART1 Bridge Plug-in
									Unchanged Firmware
									Application Transmitting and
									Receiving over UART0

1.2Loading CDC class drivers for USB

Install the setup application provided with this example and the necessary CDC class drivers will be loaded on your PC. The driver installed will work with Windows 2000 & XP

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Migration description	AN2405

only. The .inf file has to be modified to work with Windows 98/Me. When connected to a device that has CDC class implemented, Windows will see USB as a virtual COM port.

PC Application

Usbser.sys Usbser.inf

CDC Descriptors

Target Device

1.3.INF file

		Product(s)
	When a USB device is connected, windows checks the .inf file to load the appropriate driver
	for the device.	Obsolete
	their own VID & PID.
	Microsoft does not provide an .inf file with the usbser.sys driver file. The .inf file usbser.inf
	provided via the setup application allows the user to load the usbser.sys driver file under
	Windows 2000 and Windows XP. The .inf file has to be modified to work with Windows
	98/Me.
	Application manufacturers can modify this file and the device descriptors in usb_desc.h for
		-
	Product(s)
	To install the drivers from a directory instead of running the provided setup application, copy
	the usbser.inf file and usbser.sys file to a folder. When the dialog box displaying “Found
	New Hardware Wizard” opens up, choose Install from a specific location and point to the
	folder where the usbser.inf file is copied.
Note:	Do not copy the .inf file into the windows\inf folder manually.
1.3.1	Usbser.inf (Windows 2000,XP only) file:
	[Version]
	DriverVer=08/03/2004,5.1.2600.2180
	Signature=$CHICAGO$
	Class=Ports
	ClassGUID={4d36e978-e325-11ce-bfc1-08002be10318}
ObsoleteProvider=%String0%

; Port Class Install [ClassInstall] AddReg=USBClassInstall

[USBClassInstall]

HKR,,,,%Enumerator% HKR,,Icon,,"-23"

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