USB2SERIAL V2.0 User Manual

This is the online usermanual for USB2SERIAL V2.0 USB to Serial/RS232/RS485 converter sold on this site.

Introduction

USB2SERIAL (USB to Serial Converter Board) is a serial interface board based on the popular converterchip FT232 .The board can be used to provide Serial Interface /networking capabilities to your embedded projects. The Board can be used as either as a USB to RS485 converter Board or USB to RS232/Serial(TTL) converter Board.

The Board supports the following conversions.

• USB to Serial (TTL) (3.3 V interface)
• USB to Serial (TTL) (5.0 V interface)
• USB to RS 232
• USB to RS 485
• USB to Parallel (8bit / 4bit)
• The Board can also be used as a FT 232 Break Out Board.

Specifications

• Dimensions – 96.26MM X 42.11 MM (L X B)
• 3V or 5V interface voltage selection
• FT 232 based USB interface
• RS232 /RS 485 Selection
• Selectable RS485 transmission control using RTS/DTR pair or CBUS pins
• DB 9 Male Connector for RS232 Connection
• 2 Pin Terminal Block Connector For RS 485 interface
• RX/TX Transmission Indicator LED
• RS485 communication Indicator LED's
• Full Access to CBUS pins on FT232
• Extra ground pins
• Extra 5V and 3V VCC pins for powering other circuits

Operating System Support

USB2SERIAL will work on all major operating systems that support the FT232 chip like Windows,Linux,Mac OS etc .The examples and code samples for USB2SERIAL are tested on Windows (Windows7) and Linux OS's (Ubuntu,Linux Mint).

The frameworks like Mono and PySerial are cross platform and will work on all major OS's,tutorials and code using these frameworks will work on Mac OS too.

Installing Software Drivers

VCP Drivers

Windows/Linux and Mac OS  Virtual COM Port (VCP) drivers for FT232 can be easily downloaded from the FT232 website.

For Windows you can easily download an installer package from the Website.

D2XX Drivers(optional)

If you are planning on programming the CBUS pins available on the FT232 chip ,D2XX drivers need to be installled on your computer.

You can download D2XX drivers for your platform from FT232's Website.

Block Diagram and Description

USB2SERIAL board uses the FT232 chip from FTDI to convert the USB protocol to Serial TTL stream which is then given to either MAX232 for USB to RS232 conversion or  to MAX 485 for USB to RS485 conversion.The conversion choice is controlled by the jumper CONN1 on the board.

The TX and RX from the FT232 is connected to MAX232 and MAX485 through the selector CONN1 as shown in below figure.Selecting the jumper settings on CONN1 would enable the user to select between RS232 and RS 485 serial modes.The transmit and receive modes of the RS485 protocol chip MAX485 can be controlled either by using the CBUS pins (CBUS1 and CBUS2) or by using the RTS,DTR pin pairs.This can be selected by using the selector CONN2.

The CBUS0 pin of the FT232 is connected to TX/RX LED to indicate the transmission and reception of data by the FT232 chip

CBUS1 & CBUS2 are used to select between TX an RX modes of MAX485 in RS485 modes.They can be used separately through CONN2 if RS485 functionality is not required.CBUS3 & CBUS4 are brought outside through the connector P1.

RTS, CTS, DTR, DSR, DCD, RI are brought outside through P2.

The LEVEL SELECT jumper (k1) is used to select between 5V land 3V logic if you are directly connecting the TX and RX pins of the FT232 to a micro controller.

The board has a Male DB9 connector for interfacing with a standard PC serial port using RS232.A Terminal Block Connector(TBC) (P3) is provided for connecting to a twisted pair RS485 network.

Extra Ground pins are available at P4.K2 has Ground and VCC pins (5V and 3.3V) available for powering external circuits.

Jumper Settings- Loop Back Mode

In loop back mode, the TX of FT232 is connected to the RX of the FT232 so whatever data is transmitted is send back to the receive pin of the FT232.This can be used to check whether the FT232 is functioning properly.The jumper settings of loopback mode are set in CONN1 as shown below.

Jumper Settings- RS232 Mode

In this mode ,USB2SERIAL functions as a USB to RS232 converter.You can use this mode to communicate with legacy hardware that understands the RS232 signal levels(+15v to -15V).The jumper settings at CONN1 are shown below.You can ignore the jumper settings at the CONN2 connector for RS232 communication.

Jumper Settings- RS485 Mode (DTR/RTS)

In this mode USB2SERIAL acts as an USB to RS485  converter,The ~RTS and ~DTR pins of FT232 pins are used to put the MAX485 chip in transmit and receive mode. The jumper settings of the CONN1 and CONN2 are shown below.

Here ~RTS pin of FT232 is connected to the ~RE pin of MAX 485 and ~DTR pin of FT232 is connected to DE pin of MAX485 as shown in below figure.The RXD of FT232 is connected to the RO pin of MAX485 and TXD of FT232 is connected to  DI pin of MAX485.Jumpers are shown as red rectangles in the below figure.

Jumper Settings- RS485 Mode (CBUS Mode)

In this mode USB2SERIAL acts as USB to RS485 converter but instead of RTS and DTR pins ,CBUS pins of FT232 are used to control the transmit and receive modes of MAX485.The jumper settings of CONN1 and CONN2 are shown below.

The CBUS1 pin of FT232 is used to control the ~RE pin of MAX485 and CBUS2 pin is used to control the DE pin of MAX485.Before using this mode ,the CBUS pins should be configured to IO mode using FT_Prog.

Connecting USB2SERIAL under Windows(using PuTTY)

After connecting the USB to Serial Converter to the USB port of your PC, Open the Device Manager.
You can open the Device Manager by right clicking on the My Computer Icon and Selecting Manage. Which will open the Computer Management Window where you can select the Device Manager.

Alternatively You can go to the "Control Panel -> Hardware and Sound -> Device Manager".

After opening the Device Manager check under the Ports(COM & LPT) for USB serial Port(COM xx)

Here its (COM31) that is the number of the virtual serial port .The number may change depending upon your system or any other serial ports you have in your PC.
If you see a yellow warning symbol near the USB Serial Port it means that the drivers are missing and you have to install FT232 drivers from the FTDI website.

In order to communicate with the port you will require a terminal program like PuTTY. If you are using Windows XP it has a built in terminal program which you can use, In this example we will be using PuTTY which can be freely downloaded from its site.

Download the PuTTY executable from the site and click on it to launch the program.In windows 7 a security warning will be raised ,just press 'Run' to continue. Click on t Serial under Category to go to the serial port configuration page.

Now under “Options Controlling local serial lines”
Change the COM port to COM31 (or COM xx depending on your serial port number).
Select “None” for Parity and Flow control.

Now click on Session in the Category section and select serial as shown in the figure. The selected COM Port and Speed will appear inside the setting boxes. Click Open to start the serial connection.

Now put the USB2SERIAL in loop back mode so that TX and RX of FT232 are connected together.Now type some thing on the PuTTY console ,the characters will be echoed back as shown in the below figure.

Connecting USB2SERIAL under Linux (using PuTTY)

Connect the USB2SERIAL (USB to Serial Converter) to your computer.
Open the Terminal and type “ dmesg | tail ” without quotes in the terminal and press enter.

In the output from the terminal we can see that the Linux system has detected the chip and assigned a serial port (ttyUSB0) to it.
Please note that ttyUSB0 is similar to the COM31 and will be used to connect to the USB to Serial Converter using PuTTY. ttyUSB0 is system dependent and may change depending upon the serial ports present.

In this example we will use PuTTY to communicate with USB to Serial Converter.Check whether PuTTY is installed on your Linux system by typing “putty” in the terminal. If PuTTY is installed a window “PuTTY Configuration” will pop up.

You can also use the whereis command to check where putty is installed.

If PuTTY is not installed ,use your Linux distributions package manager to install it from the repositories.In Linux Mint/Ubuntu you can do it by typing “sudo apt - get install putty” in the terminal.

Go to the terminal and type “sudo putty” and provide the root password. The PuTTY window will pop up.

Click on the Serial under Category to go to the serial port configuration page.
Now under “Options Controlling local serial lines”
Change the /dev/ttys0 port to ttyUSB0 (or ttyUSBx depending on your serial port number).
Select “none” for Parity and Flow control.

Now click on Session in the Category section and select serial as shown in the figure. The selected ttyUSB0 Port and Speed will appear inside the setting boxes. Click Open to start the serial connection.

Now a console window will pop up .Put the USB2SERIAL board in loop back mode and type some characters into the PuTTY console.

The transmitted characters are received back (loop back mode ) and is shown on the console window.