3JTech 2.4 GHz FHSS Master/Slave Wireless RS232 / IrDA User`s
Contents
1. 9 Pin RS 232 Cables Connect one end to the PC COM port and another end to the WM COM port Power Supply Adjust the voltage to 7 6 V and connect the power adapter connector to the WM Note that this is applicable to the prototype WM board with ewd 8010 processor only Reset Button After applying the power press the reset button to start running the firmware The I Am Alive LED indicator will start to flash once per second Note that the production version WM will not need this reset button Firmware Correct version of firmware must be loaded on the Master WM and Slave WMs Note that the production version of 3JTech WM will have single flash memory containing both Master and Slave firmware and the selection is determined by the DIP switch setting Distance between Master WM and Slave WMs Adjust to proper distance for testing 9 3 Running the test tool vbterm master exe This program simulates a PC host application that controls the Master WM vbterm slave exe This program simulates a camera that controls the Slave WM Revision 1 0 1a 3 TECH 3J Tech Co Ltd Select the COM port Use the above two programs to select the COM port CommPort gt Port Configuring the PC COM port Use the above two programs to set the corresponding COM port to the following settings CommPort gt Property gt Maximum Speed and Connection Preferences 115200 baud 8 bits n2. Click on the COM port control button to open the COM port The following status indicators will be updated CTS status indicator turns green to indicate that WM is connected to the PC COM port RTS status indicator turns green to indicate PC is ready to accept input from WM Revision 1 0 iS 3 TECH 3J Tech Co Ltd Master connects to Slave Use the Dial Phone Number button The 3 from the left to select the slave ID to connect to and click on OK button to start the connection The following status indicators will be updated if connection is successful DTR on Master turns green to indicate that call request has been made to Master WM DCD on Master turns green to indicate that call request is acknowledged by the Master WM DCD on Slave turns green to indicate that call request is present DTR on Slave turns green to indicate that Slave has accepted the call from the Master If the connection is not successful a message box Timeout on DCD will appear after 5 seconds Slave connects to Master Use the DTR button to connect to the Master The following status indicators will be updated if connection is successful DTR on Slave turns green to indicate that call request has been made to Slave WM Ring with slave ID appears on Master scrolling window area to indicate that the slave is calling the master DTR on Master turns green to indicate that Master has accepted the call from the Slave DCD on Master turns green to
3. 0 Initially the WM on the PC side holds DCD low and the PC holds DTR low because there is no connection 1 The RS232 Device drives DTR high to request its WM slave to make a connection to the master The RS232 Device s WM slave initiates a connection to the PC s WM master The PC s WM issues the following message RING xxxxx CR xxxxx slave serial If it wishes to accept the connection the PC raises DTR The PC s WM master completes the call acceptance with the slave WM Since there is now a connection in place both master and slave WM drive DCD high Ov vee ua tS 10 3 3 3 Disconnection The WM s will maintain the connection as long as DTR on both sides is held high If either side PC or RS232 Device wishes to tear down the connection it will lower DTR on its side The appropriate WM will initiate call tear down When the call is torn down each WM will lower DCD to indicate the dropped connection Both RS232 Device and PC should then hold DTR down until the next connection is desired or accepted Revision 1 0 s 3 TECH 3J Tech Co Ltd 10 4 Illustrations Please see the attached Visio drawing which documents the timing waveforms described in this memo Wireless Modem Handshaking Scheme Version 0 Master Initiated Sends slave serial Je sey DTR DCD e e S DTR Slave Initiated DCD RING slave serial gt Jejse w DTR DCD e els DTR Revision 1 0 20
4. indicate that call request is acknowledge by the Master WM DCD on Slave turns green to indicate that call request has been accepted by the Master If the connection is not successful a message box Timeout on DCD will appear after 5 seconds Call Termination Use the DTR button to disconnect the call When the call is terminated the Status indicators will be updated Both DCD and DTR status indicators turns red to indicate Signal is deasserted Log screen contents Screen contents can be logged to a file This feature can be used for comparing the text file transfer result See below Key input and screen display After a connection is established between the Master and a slave key input on one end of the connection will be displayed on the other end Use Comport properties gt Echo on to allow local echoing If there is no connection available key input will not be sent to the other end Text File Transfer After a connection is established between the Master and a Slave text file transfer can take place VB application will scroll the text received on its window You can log the screen contents from the start to the end of the file transfer and do file compare to verify the file transfer result Revision 1 0 16 3J Tech Co Ltd 3 TECH Note Be sure to turn on hardware flow control before doing the file transfer Also VB application can be modified to just capture the received data and save it to a file di
5. 3JTech 2 4 GHz FHSS Master Slave Wireless RS232 IrDA User s Manual amp Programming Guide Revision 1 3 3J Tech Co Ltd 342 Fushing N Rd 2F Taipei Taiwan A3J Eng Inc 15344 E Valley Blvd Suite C City of Industry CA 91746 USA Revision Date 3 TECH 3J Tech Co Ltd Revision History Changes 1 0 1 1 1 2 1 3 2002 1 11 3 6 01 3 9 01 8 11 01 First Release PP Corrected of slave devices added more info regarding RS 232 specs HH Added section on testing HH Change 8 N 2 to 8 N 1 Revision 1 0 3 TECH 3J Tech Co Ltd Table of Contents 1 10 INTRODUCTION Ep 4 SYSTEM FEATURES erp 5 I ODE R 0s 5 RS 232 SERIAL LINE SPECIFICATION eeeeeee eese estes tn tensa sensns tss insunt tss intus ses su sassone sens tato sassu senatus nao 6 MASTER SLAVE LOCKING AND CONNECTION eeeeeeeee eee eee enen statuens tatnen sins taste sensns ses tn sense tatus enata an 6 COMMUNICATION BETWEEN PC APPLICATION amp MASTER WM eee esee eene tn ennt tntn attain sensi tntnan 7 6 1 Slave COnfiQuration Comahds o coe rte reto e UP CERO OI Oe oco eee DRE 7 6 2 Connection Comhafidsus oet dose Hr y o ARR dea dank NH E etwas ee edes eet Ie e Clo de eves 7 6 3 Status Inquiry Commands sse eene eene tetnetre tret eeetre tritt etrr erts trit re treten etre EErEE Enere 7 CO
6. MMUNICATION BETWEEN RS232 DEVICE amp SLAVE WM eeeeeeeeeeeee teens statuens ttn tn nensis iustas instan 8 TESTING OF THE WM SYSTEM e eeeeeeee sensn neta statu nts tatus tes tn sens testa ens ta sensns ta senten sensn ases eso vossos sossa su sesoses 8 EXAMPLE OF PROGRAMMING WIRELESS MODEMS USING 3JTECH S CAMIT 10 Od IniFOuleliof eite e toti ttd intet De Mr tot M T S 10 9 2 Settingup the equipments Em 14 9 3 Running the test tool 23 ct in o etre drei tee e eer aie T N ete a a n a 14 COMMUNICATION PROTOCOLS eese eese eene entente sth sensns tn s tns ta sistunt tss tatus ses ensens estas sn sta senses sns ens tatnen 18 HISE TUTUP M 18 PIED euo m MI 18 10 3 PLOCCAUIES ME 18 10 4 BITE TD E 19 Revision 1 0 3 TECH 3J Tech Co Ltd 1 Introduction This document presents the user s manual and programming guide for a digital 2 4 GHz frequency hopping spread spectrum wireless expansion module for RS232 and IrDA in master and slave mode The main purpose of this device is to extend the range of RS232 and IrDA communication as well as providing a multipoint environment Revision 1 0 3 TECH 3J Tech Co Ltd 2 System Features 2 4 GHz Frequency Hopping Spread Spectrum One 115 2Kbit full duplex channel Point to Multi point communication Range 2000 Fee
7. Master and a Slave That is to say that two slaves can not connect or send data between each other A given Master may connect to only one Slave at a time although multiple Slaves may be locked to the same Master A Slave can only lock to one Master Locking and connecting are two important concepts related to the establishment of connections between Wireless Modems Locking refers to listening to another device or being prepared to make a data connection Connecting refers to actually making a data connection to another device Only Slave devices lock to a Master Slaves do not lock to other Slaves and Master devices do not lock and usually they are unaware of the lock status of their own Slaves A Slave may only lock to one Master at a time The Slave will remain locked to that Master until it looses RF contact with that device Once it looses RF contact it will try to find a Master to lock to In order to make a connection between a particular Slave and a Master the Slave must already be locked to that Master A Slave may only connect to a single Master which is the Master that it 1s locked to The Slave determines which Master to lock to by listening for its own the slave s serial number to be broadcast by a Master The Slave will lock to whichever Master broadcasts the slave s address Therefore it is a configuration error to configure more than one Master to control the same Slave Ifa Slave does not detect its o
8. d Raw data throughput tested by transferring large files using Z Modem protocol Data rates for uni directional and bi directional transfers will be stated Data rates at various levels of RF signal quality will be stated Performance under degraded RF reception conditions Slave locking connection request re establishment of link and throughput will be tested FCC Part 15 compliance unofficial testing This test is designed to generate confidence that the design will pass official FCC testing It is not a substitute for actually performing the official tests Revision 1 0 10 3J Tech Co Ltd 3 TECH 9 Example of Testing Wireless Modems using 3JTech s CAMit 9 1 Introduction This test tool is designed to test the 3JTech Wireless Modem WM for CAMIt product A basic test configuration is illustrated below z Modem Desktop System o Modem Modem Modem il Desktop System In the above diagram the top PC controls the Master WM and the bottom PC controls three Slave WMs The top PC downloads the slave WM Slave IDs to the Master WM which then broadcasts the IDs periodically When a Slave WM starts up it scans for a Master that broadcasts its ID and locks to that Master A PC application program is used here to simulate a camera for testing purpose Test Application for controlling the Master WM Notice that the application queries the serial number and b
9. een made and to which slave RS232 Device To summarize either side RS232 Device or PC may initiate a connection and either side may terminate an active connection Of course a RS232 Device initiating a connection may only connect with the PC This means that a slave WM will connect with the master WM The RS232 Device need not inform its WM where to make the connection because there is only one possibility However the master WM must inform the PC which RS232 Device has just initiated a connection The scenario where the PC initiates the connection raises different requirements The PC must instruct its WM the master which slave to connect to The slave WM must inform its connected RS232 Device that a connection has just been established to the PC 10 3 Precedures 10 3 1 General First PC and RS232 Device should drive DTR high to command the attached local WM to establish a connection and low to issue a command to tear down a connection The WM should drive DCD high to indicate a successful connection establishment and low to indicate a connection tear down 10 3 2 Use of AT Commands for Communication of Slave Serial s Revision 1 0 18 3J Tech Co Ltd 3 TECH In addition to the signals DTR and DCD the PC application should issue and receive certain specific AT commands during the period when DTR is low The following AT commands will be used ATD lt slave serial gt lt CR gt will be sent by the master to i
10. f the finished product Revision 1 0 S TECH 3J Tech Co Ltd 4 RS 232 Serial Line Specification The RS 232 communications interface supports a specific subset of protocols and capabilities of a serial line The following requirements constrain the type of RS 232 communications supported by the Wireless Modem 1 Baud Rate Fixed at 115200 bits per second Changing baud rate including auto baud detection is not supported Character format Fixed at N 8 1 No parity 8 data bits per byte and 1 stop bits Terminal Type Fixed as a DCE for both Master and Slave Connector type 9 Pin Mini Sub D female for both Master and Slave Flow Control Hardware flow control RTS CTS is required PC must monitor CTS and stop sending data when the Wireless Modem de assertes CTS The Wireless Modem monitors RTS asserted by the PC as well 6 Data transparency The data sent over the link may contain any valid 8 bit character sequence when the device is in Connected Data mode In Data mode the device does not attempt to interpret the data in the stream In Command mode only valid commands may be sent to the device oe od ad 5 Master Slave Locking and Connection In this section we discuss the concepts of Master and Slave devices and the concepts of locking and connecting A Wireless Modem may be configured as either a Master or a Slave by switching a mechanical switch Connections may only be made between a
11. ication program and WM Valid commands for Master WM are ATD xxxxx CR Dial to the slave wireless modem It will be followed by the PC driving DTR high to start the dialing The response is OK lt CR gt or ERROR lt CR gt AT amp Zn xxxxx CR Store slave serial number Where n is the nth slave serial number 0 B The response is OK lt CR gt or ERROR lt CR gt ATI0 lt CR gt View Serial Number WM will respond with Master WM s serial number The response format is SN xxxxx lt CR gt Revision 1 0 13 3 TECH 3J Tech Co Ltd ATI3 lt CR gt View ROM version WM will respond with version and build date The response format is REV bbbbyymmdd lt CR gt where bbbb is build number yy is year mm is month and dd is day Valid commands for Slave WM are ATI0 lt CR gt View Serial Number WM will respond with serial number The response format is SN xxxxx lt CR gt S0 lt CR gt Slave host queries LOCK status to see if we have locked to a host WM If locked send back LOCK lt CR gt else NO LOCK lt CR gt ATI3 lt CR gt View ROM version WM will respond with version and build date The response format is REV bbbbyymmdd lt CR gt where bbbb is build number yy is year mm is month and dd is day Note that xxxxx is slave serial number 5 bytes and CR is hexdecimal number 0x0d Invalid command will get ERROR lt CR gt response from the WM 9 2 Setting up the equipments
12. nd the Slave WM is much simpler than that between the PC application and the Master WM Whereas the Master WM may accept connections from multiple slaves a particular slave may only connect to its own master This constraint means that it is not necessary for the slave WM to specify the target of a connection request Likewise the slave WM does not need to specify the origin of an incoming connection request Please see the section on Handshaking for more information Connection to Master Command for Slave The device connected to a Slave WM does not send an AT command to cause the WM to connect to the Master Instead it simply drives DTR high and waits for DCD to go high to signal a successful connection Status Inquiry Commands for Slave ATI0 lt CR gt View Serial Number WM will respond with serial number The response format is SN xxxxx lt CR gt S0 lt CR gt Slave host queries LOCK status to see if we have locked to a host WM If locked send back LOCK lt CR gt else NO LOCK lt CR gt ATI3 lt CR gt View ROM version WM will respond with version and build date The response format is REV bbbbyymmdd lt CR gt where bbbb is build number yy is year mm is month and dd is day Note that xxxxx is slave serial number 5 bytes and CR is hexdecimal number 0x0d Invalid command will get ERROR lt CR gt response from the WM 8 Testing of the WM System Although final testing of the complete system is the
13. ndicate to which a connection is desired The slave serial number will be specified as 5 hexadecimal digits e g 123AB The PC s WM will respond with OK lt CR gt if the command was understood After OK is received from the WM the PC should drive DTR high to initiate the connection When a slave WM initiates a connection the PC s WM the master should issue the message RING slave serial gt lt CR gt to inform the PC from which slave RS232 Device to expect a connection The master WM will only accept the connection if the PC drives DTR high 10 3 3 Timing Details 10 3 3 1 Connection Initiated by PC In this case the following sequence of events should occur 1 Initially the WM on the PC side holds DCD low and the PC holds DTR low because there is no connection The PC issues the following command ATD xxxxx lt CR gt xxxxx slave serial The PC s WM responds with OK lt CR gt The PC s WM initiates a connection with the appropriate slave WM The RS232 Device s WM raises DCD to indicate an incoming connection The RS232 Device acknowledges the connection to its WM by driving DTR high Since the RS232 Device has accepted the connection the slave WM completes call acceptance with the master WM 8 Since a connection is now in place the master WM indicates this fact to the PC by driving DCD high DiQN Um SS 10 3 3 2 Connection Initiated by RS232 Device In this case the following sequence of events should occur
14. o parity 1 stop bits Hardware Flow Control Use the above two programs to turn on the hardware flow control CommPort Property gt Flow Control gt RTS Status Indicators and Control buttons There are a few status indicators on the upper area of the application GUI Red color indicates that the status is not asserted and green color indicates that the status is asserted DTR and RTS are used as both status indicator and control button CTS and DCD are status indicators only You can click on the control buttons to toggle the state of it DTR Data Terminal Ready Use this button on Slave host application to connect and disconnect from the Master On Master use Dial phone number button to connect to one of the slaves and use DTR to disconnect from the slave RTS Request to Send RTS is used to assert and deassert the RTS pin on the PC COM port This control button is not effective when the hardware flow control is turned on Turn the hardware flow control off when you need to manually control the state of the RTS pin CTS Clear to Send WM firmware asserts CTS to the PC to indicate that it is ready to receive more data from PC If hardware flow control is turned on DCD Data Carrier Detect The status is to indicate the handshaking status during call setup and termination COM port control button The control button is used to open and close PC COM port Host application opening the PC COM port
15. of the test application controls only one WM either Master or Slave and is not able to cooperate with other instances of the test application Therefore a human operator is required to operate the application to run the test cases A brief description of the test cases follows e Stability of individual WM units software amp hardware Tested by placing and disconnecting multiple data connections over an extended period of time 2 days e Stability of connection and handshaking protocol Tested by placing and disconnecting multiple data connections over an extended period of time 2 days e Reliability of slave locking protocol Tested by repeatedly power cycling a slave WM repeated for master e Operation with multiple simulated RS232 Devices Tested by placing and disconnecting multiple data connections and transferring files using Z Modem file transfer protocol e Compatibility with PC RS 232 port Inferred from successful testing using a PC e Compatibility with sample test application Inferred from successful testing using the application Revision 1 0 3 TECH 3J Tech Co Ltd Standby battery life Measured for one unit by monitoring it every 6 hours Details of battery used in test will be specified Unit to unit variability not tested Active battery life Measured for one unit by leaving it operating in data connection mode Details of battery used in test will be specified Unit to unit variability not teste
16. re are three slave IDs in the list any one of the slaves will hear its ID Revision 1 0 is 3J Tech Co Ltd 3 TECH within 1 92 seconds 0 64 sec slave ID 3 slave IDs However after power on locking may take longer than 7 68 seconds because the slave must find the correct hop channel before the locking process may begin Handshaking Protocol The handshaking protocol between PC camera and WM is defined in 3JTech Serial Line Handshaking Protocol Proposal document LED indicators Three LED indicators are used to show the operating status of the WM boards LED 1 I Am Alive indicator This LED flashes once per second to indicate that the application code is running LED2 Data Mode indicator When a call is established between a Master WM and a Slave WM this LED flashes once per second When in data mode data exchange can take place LED3 Locked indicator This is only used by the Slave WM to indicate that it has found its Master WM and it is locking to it Visual Basic Test application program The PC application program is written in Microsoft Visual Basic It implements the handshaking protocol required to instruct WM to set up and tear down a call The idea is to use it as a debugging tool during the firmware development and also as a reference for vendor s real host application development Visual Basic has been chosen for fast prototyping and ease of learning Commands and responses between Test appl
17. rectly Thus binary file transfer can be accomplished Revision 1 0 1r 3 TECH 3J Tech Co Ltd 10 Communication Protocols 10 1 Background The Wireless Modem project uses wireless modems to replace cables carrying data and control information between several digital RS232 Devices and a controlling application hosted on a PC Because the application and the RS232 Devices must be able to properly control the wireless modems the system requires a suitable communication protocol between the application and the master modem and between the RS232 Devices and the slave modems 10 2 Description The current description concerns the use of serial line RS 232 signals and messages for the purpose of controlling the wireless modems At any one moment only one slave modem may have a connection to the master As a result the controlling application must take responsibility for contacting each slave in turn to determine if it has data In this case the slave modem connected to the RS232 Device must inform the RS232 Device that a connection has been established In addition either the PC application or the RS232 Device must terminate the wireless connection whenever there is no data remaining to be sent on the connection When a RS232 Device acquires new data that it wishes to send it may initiate a connection to the application In such a case the master wireless modem connected to the master must inform the application that a connection has b
18. responsibility of the customer a certain degree of testing has been performed to ensure a minimum level of quality and development risk The Wireless Modem system has been tested in the following areas Stability of individual WM units software amp hardware Stability of connection and handshaking protocol Reliability of slave locking protocol Operation with multiple simulated RS232 Devices Revision 1 0 3 TECH 3J Tech Co Ltd Compatibility with PC RS 232 port Compatibility with sample test application e Standby battery life Active battery life Raw data throughput tested by transferring large files using Z Modem protocol Performance under degraded RF reception conditions FCC Part 15 compliance unofficial testing A complete description of the testing process is beyond the scope of this document Instead the following sections give some general information about the nature of testing performed For all ofthe tests except for the FCC Part 15 the test environment was as follows 3JTech has developed a PC application in Visual BASIC which simulates the operation of the RS232 Device and of the controlling application The application may be used to exercise the WM system in a variety of ways The number of slave WM s that may be included in the test proceedure is limited by the number of serial ports on the PC or the number of PC s Of course for RF range testing it is necessary to have more than one PC Each instance
19. t line of sight 115 2Kbit RS 232 port 115 2Kbit IrDA port Firmware available in 3Q 2001 3 AAA battery cells External AC power supply Built in battery charging LED for link verification Robust FHSS and TDMA wireless protocol Operation time 8 hours Standby time one week 12 points of wireless connection Master Slave configuration switch Master is programmed to connect to slaves e Easy add on of extra slaves 3 Intended Uses The complete system is intended as a component to be used by a product developer in constructing other complete systems or products It is not intended to be offered as a stand alone product for retail sale 3JTech also sell a stand alone product which is called RF232 for direct replacing RS232 cable RF232 is sold as a pair of wireless modem This document describe the usage and programming for the master slave mode wireless communication through serial ports When incorporating this system into a product or when offering the system as an accessory to a product the product developer must take responsibility for verifying that the entire system product plus Wireless Modem sub system will operate as intended Such responsibility would include testing the complete system specifying resulting operational characteristics modifying the product s hardware or software to be compatible with the Wireless Modem and possibly modifying the Wireless Modem hardware or software to accommodate additional requirements o
20. that should be locked to it The PC sends the following command to tell the PC that the indicated slave should lock to this master AT amp Zn xxxxx CR Store slave serial number Where n is the nth slave serial number 0 B The response is OK lt CR gt or ERROR lt CR gt The PC informs the WM that it should no longer retain a certain slave by issuing the same command with the slaveID set to all zeros AT amp Zn 00000 lt CR gt Connection Commands The PC instructs its WM to connect to a particular slave by issueing the command ATD xxxxx lt CR gt Dial to the slave wireless modem It will be followed by DTR high to start the dialing The response is OK lt CR gt or ERROR lt CR gt The PC Answers the incoming call request from one of the slaves by driving DTR high Status Inquiry Commands for Master ATI0 lt CR gt View Serial Number WM will respond with Master WM s serial number The response format is SN xxxxx lt CR gt ATI3 lt CR gt View ROM version WM will respond with version and build date Revision 1 0 3 TECH 3J Tech Co Ltd The response format is REV bbbbyymmdd lt CR gt where bbbb is build number yy is year mm is month and dd is day Note that xxxxx is slave serial number 5 bytes and CR is hexdecimal number 0x0d Invalid command will get ERROR lt CR gt response from the WM 7 Communication between RS232 Device amp Slave WM The communication between the RS232 Device a
21. uild information from the WM when the COM port is opened The window title bar is updated with the serial number Revision 1 0 B 3JTECH 3J Tech Co Ltd Z Wireless Modem Master SN 54321 File CommPort MSComm Call en P DTR RTS CTS DCD VE Mess fed n e e o o e 13 58 24 Download slave serial number 00000 OK OK 13 58 24 Download slave serial number 11111 OK OK 13 58 24 Download slave serial number 22222 OK OK 13 58 24 Download slave serial number 33333 OK OK 13 58 24 Download slave serial number 44444 Test Application for controlling the Slave WM Notice that the application queries the serial number and build information from the WM when the COM port is opened The window title bar is updated with the serial number Test application will periodically query the LOCK status from the WM slave If the Slave WM can still hear from its Master LOCK reponse will be returned Otherwise UNLOCK status is returned Z Wireless Modem Slave SN 11111 DE Xx File CommPort MSComm Call a al amp DTRRIS CTS DCD S 9 Eds e s Status Settings 115200 n 8 2 00 00 13 Slave ID Broadcast The slave IDs are broadcasted periodically by the Master WM Every 640 msec the next slave ID in the slave ID list is transmitted Since a single Master WM can control up to 12 Salve WMs a slave will be able to hear its ID no later than 7 68 seconds 0 64 sec slave ID 12 slave IDs For example if the
22. wn serial number broadcast in a certain time period it will put itself to sleep temporarily and try again later A Master may have up to 12 slaves locked to it at any point in time Revision 1 0 3 TECH 3J Tech Co Ltd A connection may be initiated by either the Master or a Slave by sending AT commands to the Wireless Modem over the RS 232 interface and by asserting the DTR pin The commands and protocol used by the Master differ from those used by the Slave Of course if a connection is already in progress between the Master and another slave a connection attempted by a slave will be rejected by the Master The Master will not attempt a 2 connection when there is already one in progress 6 Communication between PC Application amp Master WM In the discussion that follows we assume that a PC is connected to a Master and that there are multiple RS232 Devices each connected to a Slave The PC may control the establishment of connections between the Master WM and the various Slaves The communication protocol used has a format similar to ordinary modem AT commands All of the commands are sent using the same serial line discipline as for data mode N 8 1 115200 bps There are 3 types of messages or commands exchanged between the PC and the Master WM These are slave configuration commands status inquiry commands and connection commands Slave ID Configuration Commands for Master The PC informs its WM of the various slaves
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