Copyright: Copyright (c) 1997 Teledesign Systems Inc.


Contents
 AirTest Help Contents

 	Introduction

Setup

Menus

Comm Port Window

PC Systems Requirements

Trouble Shooting

Serial Port Basics

Contacting Teledesign

Copyright (c) 1997 Teledesign Systems Inc.


Menu_Port
Port Menus

Open Comm Port X - Open the PC comm port.  This menu changes to a Comm Port X menu when the port is opened.

Comm Port X - Select the port as the active port (port window with the focus).  The active port has a check mark next to its menu.

The following menus act on the active port window.

Start - Start a transmission.

Pause - Pause the transmission.

Stop - Stop the transmission.

Send Error - Send a transmit error.

Clear Screen - Clear the Tx Message, Tx Data and Rx Data text boxes.

Show Status - Toggles open or closed the status panels at the bottom of the port window.

Close Port - Close the port.

Exit - Exit AirTest.  AirTest closes any open ports before exiting.


Menu_Setup
Setup Menus

Test Setup - Open the test setup screen used to set the type of test.

Port Setup - Open the port setup screen used to control the comm port settings.

Control Line Setup - Open the control line setup screen used to set the operation of the comm port control lines.


Menu_Window
Window Menus

Tile - Tile the open port windows.

Tile Horizontally - Tile the open port windows horizontally.

Tile Vertically - Tile the open port windows vertically.

Cascade - Cascade the open port windows.

Comm Port List - This list shows all the open comm ports.  The active comm port has a check next to its menu.  Selecting a menu makes that comm port active.


Menu_Help
Help Menus

Contents - AirTest help contents.

Index/Search - AirTest help index with search capability.

Using Help - How to use help.

About AirTest - Show the About AirTest screen.


Port_Window
Comm Port Window

Click on the control of interest for more information.


Setup

PC to Modem Connection

The PC and modem serial ports are connected using a standard serial cable.  The most common type of this cable has a 9 pin subminiature D connectors on both ends and is a straight through cable (i.e. pin 1 to pin 1, pin 2 to pin 2, etc).  If either the PC or modem uses a 25 pin connector then a standard 9 to 25 pin serial port adapter can be used.  See RS-232 Serial Port Basics.

Open PC Comm Port

The PC comm (serial) port windows are opened with the Open Comm Port menus under the Port menu (see Port Menus).

AirTest Setup

AirTest has three setup screens which are opened using the Setup menu.

Test Setup - Set the type of test to be run.  If two PCs are used then the test settings for both versions of AirTest must match.

Port Setup - Set the serial port settings.  These settings should match the modem settings.

Control Line Setup - Set the operation of the serial port control lines.


Setup_ControlLine
Control Line Setup

Click on the control of interest for more information.


Setup_Port
Port Setup

Click on the control of interest for more information.


Setup_Test
Test Setup

Click on the control of interest for more information.

The tests selected for the receiving and transmitting modems must be the same (if the two modems are tied to different computers).


Menus

     Port Menus

     Setup Menus

     Window Menus

     Help Menus


Setup_Port_BaudRate
Baud Rate - Selects the baud rate of the comm ports.


Setup_Port_Parity
Parity - Selects the type of parity used by the comm ports.


Setup_Port_StopBits
Stop Bits - Selects the number of stop bits used by the comm ports.


Setup_Port_DataBits
Data Bits - Selects the number of data bits used by the comm ports.


Port_Window_StatusBtn
Status Button - Toggles open and closed the status panels at the bottom of the port window.


Port_Window_ClrScrnBtn
Clear Screen Button - Clears the Tx Message, Tx Data and Rx Data text boxes.


Port_Window_ErrorBtn
Transmit Error Button - Sends a single transmit error.


Port_Window_TxBtn
Transmit Buttons - Start, pause and stop for transmissions.


Port_Window_TxMsg
Tx Message Box - Shows the message to be transmitted (only available in Chat mode).


Port_Window_TxData
Tx Data Box - Show the transmit data.  The size of this box can be adjusted by moving the bar between the tx data box and the rx data box.


Port_Window_RxData
Rx Data Box - Shows the receive data.  The size of this box can be adjusted by moving the bar between the tx data box and the rx data box.


Port_Window_LEDs
LED Indicators - Indicate the state of the serial port lines.  The lines driven (outputs) by the PC use a red LED and the lines received (inputs) use a green LED.


Port_Window_StatusCmd
Status Bars - Shows the status of the port.  Clicking these will open or close the status panels.


Port_Window_TxStatusPnl
Transmit Status Panel - Displays the transmit status parameters.  The panel can be opened and closed by pressing the transmit status bar or by pressing the status button (on the tool bar).


Port_Window_Reset
Reset Buttons - Resets the values on the status panel.


Setup_ControlLine_TxDCD
Do not tx over DCD - If active, AirTest does not transmit when DCD is active.


Setup_ControlLine_CTS
Use CTS for transmit flow control - If active, AirTest waits for CTS before sending transmit data.


Setup_ControlLine_RTS
Activate transmit with RTS - If active, transmit bursts are framed with RTS.  Otherwise RTS will always remain inactive.


Setup_ControlLine_TxWaitTime
Wait fixed time before sending data - If active, AirTest waits the designated time after RTS is activated before sending data.  If inactive, data is sent immediately after RTS is activated.


Setup_ControlLine_RxPktSep
Receive packet separation - This controls how AirTest determines the breaks between receive bursts.

Use DCD - DCD is used to frame the receive bursts.

Time - A break between bursts occurs when no data is received for the set amount of time.


Setup_Test_Chat
Chat - This tests allows the user to enter and send text messages.


Setup_Test_SingleChar
Single Character - This test sends bursts of a single character.  The number of characters in the bursts is set with the Message Length control.  The time between bursts is set with the Message Repeat Time control.


Setup_Test_Repeated
Repeated Message - This test sends the defined message repeatedly.  The time between the messages is set with the Message Repeat Time control.


Setup_Test_RndmFixed
Random Data with Fixed Message Length - This test sends bursts of a random characters.  The number of characters in the bursts is set with the Message Length control.  The time between bursts is set with the Message Repeat Time control.  Note that with this test two header characters are sent with each burst.


Setup_Test_RndmRndm
Random Data with Random Message Length - This test sends bursts of a random characters.  The number of characters in the bursts is also random from 1 to the setting of the Message Length control.  The time between bursts is set with the Message Repeat Time control.  Note that with this test two header characters are sent with each burst.


Setup_Test_MsgLength
Message Length - This control sets the number of characters in a transmit message.


Setup_Test_MsgRepeatTime
Message Repeat Time - This control sets the amount of time between transmit messages.


Setup_Test_PktNumber
Send and Receive Packet Number - When enabled a two character incrementing packet number from 1 to 99 is added to the beginning of each message.  This allows the user to determine if messages are lost or repeated.


Intro
Introduction

AirTest is provided free by Teledesign Systems so that our customers and potential customers can test, evaluate and compare their wireless communications equipment.  We hope that you find this software useful and easy to use.  If you have questions or comments, please contact Teledesign Systems through one of the means listed.

AirTest can be used to send chat messages between several modems or it can be used to run automated tests which send data and monitor the results.  With the automated tests, AirTest will automatically monitor and calculate the Bit Error Rate (BER) of the link to provide a measurement of the quality of the wireless link.

See Setup for information on how to configure AirTest for operation.


Trouble Shooting

Transmit does not send data:

The cause of this is usually shown in the transmit status box at the bottom of the port window.

1) Tx: Wait for DCD.  The transmission is waiting for the DCD line to become inactive (which typically indicates that the modem is receiving data).  This wait state can be disabled by turning off the "Do not transmit over DCD" control on the control line setup screen.

2) Tx: Wait for Rx.  The transmission is waiting until it stops receiving data from the modem.  This wait state can be disabled by turning off the "Do not transmit while receiving" control on the control line setup screen.

3) Tx: Wait for CTS. The transmission is waiting for the CTS line to become active.  This wait state can be disabled by turning off the "Use CTS for transmit flow control" control on the control line setup screen.

4) Tx: Timed Wait.  The transmission is waiting the set time before transmitting.  This wait state can be disabled by turning off the "Wait fixed time before sending data" control on the control line setup screen.  Alternatively, the time can be adjusted.

Receive does not sync up to the BER test:

1) This can be due different test settings between the transmit and receive versions of the AirTest software.  Use the test setup screen to make the necessary adjustments.

2) The AirTest port setup does not match the setup of the modem.  This causes invalid receive characters.  This can normally be detected because there will be Parity/Framing Errors.

3) There are too many characters and/or messages with errors.  This is normally caused by an unreliable modem link.

Parity/Framing errors:

This is usually caused by an incorrect port setup.

1) The AirTest port setup does not match the setup of the modem.

2) The port setup is different between the modems at each end of the test.

Multiple receive messages are received together:

1) This can be caused by too high a setting for the Rx Packet Separation time which is set on the control line setup screen.

A) Decrease the receive packet separation time.

B) Change the setup to use DCD to separate receive packets.

2) This can also be caused by a slow computer.  In this case the computer is not fast enough to detect the separation between receive packets

A) Close all other programs running on the computer.  Including any DOS TSR (Terminate and Stay Resident) programs which run in background.

B) Do not have transmit and receive simultaneously running on the same port.

C) Minimize your interaction with the computer while the test is running (minimize mouse movement and button clicks).

D) Use a faster PC (faster processor or more memory).

Sync losses:

Sync losses occur when the receive side gets too many characters and/or messages with errors.  This is normally caused by an unreliable modem link.

Overrun errors:

Overrun errors are when receive characters are lost because the computer does not process the receive interrupts quickly enough. This is normally caused by the computer being too slow computer to respond to all the events which occur.

1) Close all other programs running on the computer.  Including any DOS TSR (Terminate and Stay Resident) programs which run in background.

2) Minimize your interaction with the computer (mouse movement and button clicks) while the test is running.  Mouse movement is especially taxing on the computer because it causes a larger number of high priority interrupts.

3) Do not run two ports or transmit and receive simultaneously.

4) Use a serial port card which has a 16550 UART (as opposed to an 8250 or 16450).  16550 UARTs have a receive buffer which reduces the serial port event processing requirements on the PC.

5) Use a faster PC (faster processor and/or more memory).


RS-232 Serial Port Basics

See also: 	RS-232 Pinouts

RS-232 Signal Levels

PC Serial Ports

Serial ports on PCs are DTEs which use female 9 or 25 pin subminiature D connectors.

Modem Serial Ports

Most modems (both wired and wireless) are DCEs with male 9 or 25 pin subminiature D connectors.

PC to Modem Interface Cable

The PC and modem serial ports are connected using a standard serial cable.  The most common type of this cable has a 9 pin subminiature D connectors on both ends and is a straight through cable (i.e. pin 1 to pin 1, pin 2 to pin 2, etc).  If either the PC or modem uses a 25 pin connector then a standard 9 to 25 pin serial port adapter can be used.

RS-232 Standard

The EIA (Electronic Industries Association) RS-232C standard is a standard for short distance (less than 50 feet) serial communications.  The standard defines the electrical signal levels, interface characteristics and the operation of the control signals (handshake lines).  Although the standard defines the operation of the handshake lines, there is significant variation in the way these signals are used by different equipment.

Connectors

The RS-232 standard does not require the use of a specific connector.  However, most asynchronous RS-232 serial ports use either a 9 pin or 25 pin subminiature D connector.  The same signals are provided with both connectors, but of course the pinouts are different.

DCE vs. DTE

RS-232 serial ports come in two varieties; DCE (Data Communications Equipment) and DTE (Data Terminal Equipment).  This defines the direction of the serial port's lines (driven or received).  It also typically defines the polarity of the connector.  DCE's typically use female pin connectors and DTEs typically use male pin connectors.

Connecting a DCE to a DTE is the most common setup and requires a standard straight through cable (i.e. pin 1 to pin 1, pin 2 to pin 2, etc.).  When connecting two DCEs or two DTEs together a null modem cable is required.  The purpose of a null modem cable is to cross connect the appropriate signals.  However, null modem cables are not all the same and therefore it is important to verify that a specific cable is appropriate for a specific application.

Asynchronous Data

Most RS-232 ports are asynchronous (as opposed to synchronous).  Asynchronous ports do not use clocks or timing signals to synchronize data transfers.  Instead data is framed into asynchronous characters which the ports then synchronize to.

An asynchronous character consists of a start bit, data bits and stop bits.  The start bit indicates the beginning of a character.  The number of data bits varies, but is typically between 7 and 9 bits.  The data bits sometimes include a parity bit which provides error check information with each character.  The number of stop bits also varies but is typically 1 or 2 bits.

Flow Control

Flow control is the method for controlling the flow of data between the DCE and DTE.  Flow control is used to prevent the DTE and DCE data receive buffers from overflowing.  There are several methods used for flow control and as with everything related to RS-232 there is no one standard.  The two main variations of flow control are hardware flow control which uses the

RS-232 handshake lines and software flow control which uses characters sent along with the normal data.

Hardware Flow Control

Hardware flow control typically uses two control lines, one for each direction fo data.  When a port activates its flow control signal it is indicating its readiness to receive data.  Deactivating the flow control signal indicates that the port can no longer receive data because its buffer is full or close to full.

The most common form of hardware flow control and the one used by most full duplex wired (as opposed to wireless) modems is RTS/CTS.  With RTS/CTS flow control, RTS provides flow control for the DTE and CTS provides flow control for the DCE.  One problem with RTS/CTS flow control is that for many half duplex modems (most wireless modems) the RTS signal is used to frame transmit data going from the DTE to the DCE.  This use of RTS conflicts with using RTS for flow control of data to the DTE.

An alternative form of hardware flow control is DTR/DSR.  With DTR/DSR flow control, DTR provides the flow control for the DTE and DSR provides flow control for the DCE.

Software Flow Control

Software flow control uses characters sent over the data lines to control data flow.  These characters are sent along with the normal flow of data between the DTE and DCE.  There is typically one character which is used to stop the flow of data and a different character to restart the flow.  Software flow control can use any characters to start and stop flow.  However, the most common characters used are the ASCII XON (starts flow) and XOFF (stops flow) characters.  Because these are the most common characters used, software flow control is often referred to as XON/XOFF flow control.  The ASCII XON character is the decimal character 17 (0x11 hex) and is also known as DC1 or Ctrl-Q.  The ASCII XOFF character is the decimal character 19 (0x13 hex) and is also known as DC3 or Ctrl-S.

A problem with software flow control is that the normal data passed over the communications link cannot include the flow control characters.  If it does, the flow of data will be incorrectly stopped or started.  This limits the characters which can be used by the host application and also prevents the sending of binary (all character numbers) data.


Teledesign Systems Inc.

Teledesign Systems Inc. can be reached during our normal business hours of 8 AM to 5 PM (Pacific Standard Time) Monday through Friday.

Phone numbers:

(800) 663-3674 or (800) MODEMS4 (USA & Canada only)

(408) 436-1024

(408) 436-0321 Fax

Internet:

www.teledesignsystems.com

Email:

corpcomm@teledesignsystems.com


RS-232 Serial Port Pinouts

RS-232 Pinouts

	Connector		Direction
Signal	9 Pin	25 Pin	DCE	DTE
SG	5	1, 7	--	--
TXD	3	2	Input	Output
RXD	2	3	Output	Input
RTS	7	4	Input	Output
CTS	8	5	Output	Input
DCD	1	8	Output	Input
DSR	6	6	Output	Input
DTR	4	20	Input	Output
RI	9	22	Output	Input

RS-232 Signal Description

Signal	Description
SG - Signal Ground	Ground
TXD - Transmit Data	Data from the DTE
RXD - Receive Data	Data to the DTE
RTS - Request to Send	Control from DTE requesting to transmit data.
CTS - Clear to Send	Response from DCE indicating a readiness to receive transmit data.
DCD - Data Carrier Detect	Status from DCE indicating that it is receiving data.
DSR - Data Set Ready	Status from DCE indicating that it is operational.
DTR - Data Terminal Ready	Status from DTE indicating that it is operational.
RI - Ring Indicator	Status from DCE indicating a ring condition.
Note: This table indicates the standard operation of the control lines.  There is significant variation in the way these signals are used by different equipment.


RS-232 Serial Port Signal Levels

RS-232 Signals Levels

	Level	(volts DC)
Direction	Low	High
Drivers	-15 to -5	+5 to +15
Receivers	-25 to -3	+3 to +25

RS-232 Signal Polarity

Voltage Level	State
Low	Mark
	Control signal inactive
	Stop bit state
	Logic one data bit state
High	Space
	Control signal active
	Start bit state
	Logic zero data bit state


Bit Error Rate
Bit Error Rate Test

The BER test result is shown in the receive status panel.

A BER (Bit Error Rate) test is used to determine how noisy a link is for data operation.  The result tells what percentage of bits are corrupted.  A BER of 3 x 10-4 means that 3 out of 10,000 (104) bits are corrupted.

The longer a BER test runs the more accurate the result.  To get an accurate result a BER test should run until at least 100 errors have been received.  This provides a 90% confidence level in the BER result.  However, for relatively error free operation this can take too long to run.  An alternative is to run the BER test until at least 10 errors have been received which provides a 68% confidence level.


Setup_ControlLine_NoTxWhileRx
Do not transmit while receiving - If active, AirTest does not transmit while receiving data.


Port_Window_RxStatusPnl
Receive Status Panel - Displays the receive status parameters.  The panel can be opened and closed by pressing the receive status bar or by pressing the status button (on the tool bar).


PC_System_Requirements
PC Systems Requirements

•	Processor: 80486 or higher (Pentium recommended).

•	Operating System: Windows 3.1, Windows 95, Windows NT.

•	Memory: At least 4 MB (8 MB recommended).

•	Free Hard Disk Space: 4 MB


Port_Window_RxStatusParam
Receive Status Parameters

Msgs: The number of messages (bursts) received.  For test setups which measure BER, the number of messages in error is also displayed.  How messages are separated is controlled with the receive packet separation settings.

Bits: The number of bits received.  For test setups which measure BER, the number of bits in error is also displayed.  This number only includes the bits after AirTest has synchronized to the incoming data.

Parity/Framing Errs: The number of parity or framing errors detected.  Note: If many errors occur close together, they may not all be detected.

Msg Overrun Errs: This indicates the number of messages which have had receive overrun errors.  An overrun error is when receive data is lost because the PC does not process the receive data interrupt quickly enough.  Messages which have overrun errors are not used in the calculation of BER.

BER: The Bit Error Rate of the link.

Sync Losses: The number of times that the BER test has lost synchronization.  This occurs if there are a large number of errors in the received data.  This parameter is only displayed for setups which measure BER.


Port_Window_TxStatusParam
Transmit Status Parameters

Msgs: The number of messages (bursts) transmitted.

Bits: The number of bits transmitted.


License
AirTest License

By using this Software, you are agreeing to be bound by the terms of this agreement. If you do not agree to the terms of this agreement do not use the software.

1) USE AND COPIES.  You may install and use an unlimited number of copies of this Software ("Software" refers to all the program files and documentation) and you may also make unlimited copies of the software and give them away as long as you meet the following requirements.

A) The Software is not modified in any way.

B) Any copies are provided with all the necessary (included) files and documentation.

2) RESTRICTIONS.  You agree not to sell, rent or lease the Software.  You also agree not to modify, reverse engineer, decompile, or disassemble the Software.

3) COPYRIGHT.  This Software is owned by Teledesign Systems Inc. and is protected by United States copyright laws and international treaty provisions.

4) NO WARRANTY.  THIS SOFTWARE IS PROVIDED TO YOU AS IS AND TELEDESIGN SYSTEMS INC. MAKES NO WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.