Cirronet WIT 2550 Integration Manual Download Page 29 | Manualshive

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WIT2450

©

2000- 2005 Cirronet

™

Inc

29

M-2450-0000 Rev B

4.6. Received Signal Strength Indicator

Pins 9 and 13 allow real-time assessment of received signal strength. The graph above
shows the relationship of the analog RSSI output voltage from Pin 9 vs. LNA input
power. The RSSI is approximately linear from -100 dBm to -31 dBm. The voltage level
at -100 dBm is .2V and the voltage level at -31 dBm is 1.25V which is the maximum
output voltage as shown in the chart. These values would correspond to

0FH

and

60H

when using the

wr

command in Section 5.2 Network Commands.

The RSSI Strobe output indicates when a valid RSSI signal is present and a high signal
indicates a valid RSSI. The figures below show the relationship between the RSSI signal
and the RSSI Strobe output.

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Summary of Contents for WIT 2550

Page 1: ...WIT2450 2 4GHz Spread Spectrum Wireless Industrial Transceiver Integration Guide 3079 Premiere Pky Ste 140 Duluth Georgia 30097 www cirronet com 1 678 684 2000 ...

Page 2: ...se systems must also be informed that RF exposure limits may be exceeded if personnel come closer than 2 m to the apertures of any of these antennas Notice to users installers using the following mobile antennas with Cirronet RF products Mobile Mark 12dBi omni directional Mobile Mark 9dBi omni directional MaxRad 5dBi whip Cirronet Patch antenna Ace 2dBi dipole Mobile Mark 2dBi Stub The field stren...

Page 3: ...on States Norway Switzerland Use of the WIT2450 in France When used in France the WIT2410 can only be operated with the France hopping pattern selected This is accomplished by setting the pe parameter to 6 Refer to European Union Settings in this manual for details Canadian Department of Communications Industry Canada IC Notice Canadian Department of Communications Industry Canada IC Notice This a...

Page 4: ...2 3 4 Co Existing with 802 11b Networks 23 2 3 5 European Union Settings 23 3 PROTOCOL MODES 24 3 1 1 Data Packet 25 4 MODEM INTERFACE 26 4 1 Interfacing to 5 Volt Systems 27 4 2 Evaluation Unit and OEM Module Differences 27 4 3 Three Wire Operation 27 4 4 Power On Reset Requirements 28 4 6 Received Signal Strength Indicator 29 5 MODEM COMMANDS 30 5 1 Serial Commands 31 5 2 Network Commands 34 5 3...

Page 5: ...ation 59 10 1 2 Power Specifications 59 10 1 3 RF Specifications 59 10 1 4 Mechanical Specifications 59 10 2 Serial Connector Pinouts 60 10 3 Approved Antennas 60 10 4 Technical Support 61 10 5 Reference Design 62 10 6 Mechanical Drawing WIT2450 63 11 WARRANTY 64 Conventions All Hexadecimal Numbers are written in New Courier font 10 pt Bold as shown here 30H ...

Page 6: ...e free use and worldwide compliance A simple serial interface supports asynchronous data up to 230400 bps An on board 1 KB buffer and an error correcting over the air protocol provide smooth data flow and simplify the task of integration with existing applications Multipath fading impervious frequency hopping technology with 86 frequency channels Meets FCC rules 15 247 and ETS 300 328 for worldwid...

Page 7: ...ade can be described as a frequency selective notch that shifts in location and intensity over time as reflections change due to motion of the radio or objects within its range At any given time multipath fades will typically occupy 1 2 of the 2 4 GHz band This means that from a probabilistic viewpoint a conventional radio system faces a 1 2 chance of signal impairment at any given time due to mul...

Page 8: ...ifficulties of broadband receivers they generally employ only a minimal amount of spreading typically no more than the minimum required by the regulating agencies For this reason the ability of DS systems to overcome fading and in band jammers is relatively weak By contrast FH systems are capable of probing the entire band if necessary to find a channel free of interference Essentially this means ...

Page 9: ...f the transmitter before any data can be sent which typically takes several seconds In summary frequency hopping systems generally feature greater coverage and channel utilization than comparable direct sequence systems Of course other implementation factors such as size cost power consumption and ease of implementation must also be considered before a final radio design choice can be made As an a...

Page 10: ...nized with the base station it must request registration from the base station The registration process identifies to the base station the remotes from which transmissions will be received and not discarded Registration also allows tracking of remotes entering and leaving the network The base station builds a table of serial numbers of registered remotes To detect if a remote has gone offline or o...

Page 11: ... transmit delay or minimum data length have been set the base station will transmit whatever data is in its buffer limited to 208 bytes or as limited by the base slot size If the base station has more data than can be sent on one hop the remaining data will be sent on subsequent hops In addition to the data the base station adds some information to the transmission over the RF link It adds the add...

Page 12: ...cket mode The remote will add address sequence and CRC bytes as in the point to point mode When the base station receives the data the base station will add packetization header bytes according to its protocol mode setting 2 2 3 Full Duplex Communication From an application perspective the WIT2450 communicates in full duplex That is both the user application and the remote terminal can be transmit...

Page 13: ... a large or variable number of remotes transmit infrequent bursts of data or in polling applications where the host will request data and wait for a response prior to moving to the next remote In CSMA mode there is no limit to the number of remote radios that can be supported The illustration below compares TDMA to CSMA wa setting Description max PN remote packet size 0 default CSMA polling FFH ma...

Page 14: ... an option if desired by setting an appropriate pn value Registration is considered enabled if the number of remotes as selected by pn is 15 decimal or less and disabled if 16 or greater The pn setting is used to determine the number of ACKs the base requires for a broadcast message but in practice values above pn0f should accommodate an unlimited number of remotes As an alternative means of track...

Page 15: ...ckoffs are 0 4 hops The collision count is reset whenever a data packet is acknowledged or a successful registration renewal occurs One drawback of the CSMA contention mode is that remotes must contend to send ACKs back to the base The transmit or persistence probability p is set by the pp command This command serves double duty to specify the contention slot transmit probability if the network is...

Page 16: ...which they must periodically renew every 256 hops aka a service interval For applications needing guaranteed bandwidth availability the TDMA operation of the WIT2450 can meet this requirement In the WIT2450 TDMA scheme each remote has an assigned time slot during which it can transmit When setting up a network keep in mind that time slot length maximum packet size and hop duration are all interrel...

Page 17: ... stripped off including start and stop bits before transmission and does not need to be considered when calculating RF capacity So in this example the total capacity per remote would be If we figure a minimum margin of safety for lost packets and retransmissions of about 20 we see that this would be more than sufficient to support 9 6 kbps of continuous data per remote It is also useful to remembe...

Page 18: ...nd the Repeater s The Root radio acts as the base radio for the entire network and establishes the timing for all of the radios in the network and all other WIT2450 radios There must be one and only one Root radio for each network and it is set as the Root using the wb3 command All other radios in the network must be informed that an S F network is being setup This is performed using the wb2 comma...

Page 19: ...ions of Repeater 1 or Repeater 2 each repeater radio with downstream repeaters is assigned a different repeat network number to avoid collisions Even though Repeaters 4 5 and 6 may be in close proximity to each other since there are no downstream repeaters they can use the same repeat network number Radio Receive wn Repeat wo Root 0 NA Repeater 1 0 8 Repeater 2 0 9 Repeater 3 0 10 Repeater 4 10 11...

Page 20: ...t Repeater in your system wb2 wn upstream network number 9 wo downstream network number XX1 m 4 Verify Link Verify that each Repeater unit is linked via DCD indicator If a unit is not linked re check the above settings and run kd4 link status command on the problem unit It takes a few seconds for the repeaters to synchronize with the system 5 Send Data With the CSC program on the Repeaters set to ...

Page 21: ...8 bytes 21 bytes 25 bytes 9600 3 bytes 4 bytes 7 bytes 9 bytes 12 bytes 14 bytes 16 bytes 2400 0 bytes 1 bytes 1 bytes 2 bytes 3 bytes 3 bytes 4 bytes baud rate 3 3ms 5ms 7 5ms 10ms 12 5ms 15ms 17 7ms hop time 2 3 Modes of Operation 2 3 1 Control and Data Modes The WIT2450 has two modes of operation Control mode and Data mode When in Control Mode the various radio and modem parameters can be modif...

Page 22: ...Power Down Mode the radio must re synchronize with the base station and re register Note This pin cannot be left unconnected If Power Down is not needed this pin must be tied to 3 3v 2 3 3 RF Flow Control Mode Because of slight differences in baud rates between transmitting and receiving hosts when sending large amounts of data 100 s of KB in one direction in a point to point application it is pos...

Page 23: ...works The hopping pattern is selected using the pe command Please refer to the section 5 3 Protocol Commands for details 2 3 5 European Union Settings When operating the WIT2450 in France a limited frequency mode must be selected The Pe6 value avoids 802 11b bands 11 12 is compliant with the French regulatory standards of 2400 2450MHz To select the limited frequency band for operation in France at...

Page 24: ...d The protocol format is selected through the Set Protocol Mode command sp Base and remote radios can use protocol modes to insure that a packet is transmitted to the base without being broken up over multiple hops The data length value in the data packet becomes the effective minimum packet length and maximum packet length for that packet Note that if the remote data length is set to a number of ...

Page 25: ...tes data Receive only CONNECT E9 32 3 byte serial number HML range DISCONNECT E9 33 3 byte serial number HML CMD_ACK E9 44 3 byte serial number HML location value CMD_NAK E9 45 3 byte serial number HML INSTRUMENTATION E9 49 6 status bytes see detailed description Transmit only CMD_GET E9 40 3 byte serial number HML parameter CMD_PUT E9 41 3 byte serial number HML parameter value 3 1 1 Data Packet ...

Page 26: ...nal should be asserted When negated the WIT2450 buffers receive data until RTS is asserted 0v 1 Receive data RxD enabled 3 3v 0 Receive data RxD disabled 6 DTR Input Sleeps wakes radio transceiver In sleep mode all radio functions are disabled At wake up any user programmed configuration settings are refreshed from non volatile memory clearing any temporary settings that may have been set 3 3v 1 S...

Page 27: ...n 6 DTR need to be pulled to ground on the 16 pin male header If you have the OEM module interfaced to an RS 232 transceiver RTS and DTR need to be pulled high on the transceiver side In the evaluation unit RTS and DTR are pulled high on the transceiver side so the evaluation unit will work with these signals not connected 4 3 Three Wire Operation The WIT2450 can be operated in a three wire config...

Page 28: ... Reset Requirements The WIT2450 has an internal reset circuit that provides a reset signal to the microprocessor if the supply voltage to the WIT2450 falls below 2 7 volts Operation of the microprocessor at voltages below this voltage is unspecified and can result in corruption of the program memory When the radio is first powered on there is an inrush current in excess of 250mA The power supply i...

Page 29: ...proximately linear from 100 dBm to 31 dBm The voltage level at 100 dBm is 2V and the voltage level at 31 dBm is 1 25V which is the maximum output voltage as shown in the chart These values would correspond to 0FH and 60H when using the wr command in Section 5 2 Network Commands The RSSI Strobe output indicates when a valid RSSI signal is present and a high signal indicates a valid RSSI The figures...

Page 30: ...e that indicates the new modem parameter value The commands are loosely grouped into five different categories Serial commands Network commands Protocol commands Status commands and Memory commands Each command is described in detail below In the descriptions brackets are used to denote a set of optional arguments Vertical slashes separate selections For example given the string wn 0 3f some legal...

Page 31: ...1 5 Serial Mode Setting 0 n 8 1 1 o 8 1 2 e 8 1 3 n 7 2 4 e 7 2 5 o 7 2 Set Data Rate Divisor Sets the serial bit rate between the modem and the host This command takes effect immediately and will require adjusting the host serial rate to agree Nonstandard rates may be programmed by entering a data rate divisor computed with the following formula DIVISOR 460800 RATE 1 Round all non integer values ...

Page 32: ...m radio 2 enable CONNECT DISCONNECT packets lower nibble 3 enable INSTRUMENTATION packets 4 enable RSSI for data packets rx only 5 6 upper nibble 7 The structure for the sp command is as follows sp upper nibble in hex lower nibble in hex Here is an example to enable packet mode in both directions and instrumentation mode packets using the command spØb A command of sp13 would enable packets in both...

Page 33: ...ase the RSSI and rx status will pertain to the last packet received in the hop and if the receiver is triggered by noise it is possible they will read garbage values For this reason it is preferable to use the RSSI option in received data packets at the base to monitor these statistics For consistency with the physical CTS signal bits b2 b0 are intepreted as logic low i e 0 data flow allowed 1 dat...

Page 34: ...default wn 0 3f Set Hopping Pattern or Network Number 0 default wo 0 3f Set Repeater Network Number Base Repeater wp 0 1 2 Set Transmit Power 0 10mW 10dBm 1 63mW 18dBm default 2 250mW 24dBm wr RSSI Read Receive Signal Strength wv 0 ff Reranging period ww 0 1 Base DCD Mode Enable 0 DCD always asserted default 1 Base asserts DCD when pn 1 remote registered Access Mode Set wa on the base to determine...

Page 35: ...d to distinguish between networks Set Repeater Network Number Base Repeater This is the same as Set Hopping Pattern Set Network Number but for the Repeating radios This allows you to set the downstream network number Note that the maximum value of wn supported is 3f and that this limit may be reduced for certain pe alternate frequency band settings In the repeater mode the child network that the r...

Page 36: ...r synchronizing to a new base If full handle registration is enabled the radio will pause in transmitting data to request a new handle If only ranging registration is in effect the remote will just send a ranging registration request In either case a CONNECT packet will be produced if protocol mode is enabled just as if it were a first time registration Base DCD Mode Enable Since the most general ...

Page 37: ...2 2452 0 MHz Avoids bands 11 12 French compliant Only 16 networks are supported for pe7 and above 7 2421 7 2446 8 MHz Avoids bands 1 10 11 12 8 2457 2 2449 4 MHz Avoids bands 1 6 9 2400 2 2426 1 MHz Avoids bands 6 12 A 2431 3 2456 3 MHz Avoids bands 1 2 3 11 ph 00 fe base only Set Hop Duration 90H default 10ms pk 00 d0 Set Minimum Data Length 01 default pl remote only Get Maximum Data Length read ...

Page 38: ...eter to all remotes However link time can be reduced if this value is also programmed into the remotes which use it as a starting value when scanning for the base Set Minimum Data Length This sets the minimum threshold number of bytes required to form a packet in transparent mode The radio will wait until the data transmit delay elapses before sending a data packet with less than this number of by...

Page 39: ... When used in conjunction with the minimum data length parameter this sets the amount of time from the receipt of a first byte of data from the host until the radio will transmit in transparent mode Default is 00H which causes transmission to occur without any delay When a host is sending a group of data that needs to be sent together setting this parameter will provide time for the group of data ...

Page 40: ...nce Mode Enables or disables the ability to use the in data stream escape sequence method of accessing Control Mode by transmitting the string wit2410 When this mode is set to 1 the escape sequence only works immediately after reset this is the default When set to 2 the escape sequence may be used at any time in the data stream when preceded by a pause of 20 ms For backwards compatibility with the...

Page 41: ...n of the system and the configuration is suspect Use the Store Memory command afterwards if you wish the factory default settings to be remembered the next time you cycle power or reset the radio Recall Memory Useful for restoring the power on settings after experimenting with temporary changes to data rate protocol or network parameters etc Store Memory This command is necessary after any command...

Page 42: ...pn 01 3e Set Maximum Number of Remotes base only pr 00 ff Set Packet Attempts Limit pt 00 ff Set Data Transmit Delay remote only pw 00 2f Set Base Slot Size base only xc Display Parent Base Slot Size remote only Status Commands zb 0 1 Banner Display Disable zc 0 2 Set Escape Sequence Mode zh Read Factory Serial Number High Byte zi Display Current Banner zm Read Factory Serial Number Middle Byte zl...

Page 43: ...vailable as the WIT2450 does not support software flow control When the developer s kit is shipped from the factory one HN 550 is set up as a base station and the other is set up as a remote The interface rate for both modems is set at 9600 bps The default setting for the network key allows the modems to communicate without changing any settings As a quick test separate the two modems by about 5 f...

Page 44: ...ess industrial transceivers or WIT radios WinCOM is located on the Manuals and Software CD included in the developer s kit Install WinCOM by navigating to the Software Tools directory on the Manuals and Software CD and double click on wincom2 1 exe follow the installation wizard Once it has installed open WinCOM by double clicking on the WinCOM icon on the desktop ...

Page 45: ...Under Edit Copy Paste Find search and Select All perform the familiar Windows functionality in typical fashion The Options menu contains the selections Show Comm Errors which lists any errors encountered in the PC UART Check Comm Ports on Bootup tells WinCom to verify each available port and lists them as such in the Com Port drop down field See the section entitled WinCom Tools for an explanation...

Page 46: ...s window of WinCOM verify the COM port and baud rate settings then reset the radio by hitting F1 twice Cycling power to the radio also will cause the sign on banner to be displayed unless the banner is disabled via the Banner Display Disable command zb0 The COM port and baud rate can be changed using the drop down menus on the bottom right All the available COM ports will be listed in the menu but...

Page 47: ...Configuration parameters are sent to the radio by entering them in the WinCom window after the prompt and pressing the Enter key If an invalid command or value is entered the radio will respond with Error as shown above Until the command to save the parameters m is issued the new parameters will only be valid until power is cycled or DTR is toggled by pressing the F1 key twice New parameter values...

Page 48: ...ide of the window but the character corresponding to 0xd value of the carriage return will be displayed Similarly if the Hex Mode box is checked all characters are displayed in hexadecimal format The Clear Screen button deletes all the text in the display window The Clear CTS and Clear DCD buttons reset the respective changes counters to zero After naming the file and clicking on OK the Capture Da...

Page 49: ...T2450 this allows you to see what you are typing F6 Toggles stream mode Causes WinCOM to transmit a repeating pattern of characters Useful for testing F8 Toggles binary mode Displays extended ASCII and control characters Useful for testing PgUp Sets data rate of PC serial port to next higher value Value is displayed in status line Useful when WinCOM is used to change the WIT2450 interface data rat...

Page 50: ...his selection will have the PC COM port ignore the state of CTS and transmit data When WinCOM s transmit mode is used data is sent continuously until the user stops it by clicking on Stop or pressing F6 If the second tool Single Transmit is checked clicking the Transmit button will send the Transmit String a single time There is no need to click Stop Clicking on the Transmit button a second time w...

Page 51: ...t strings can now be saved to memory using the save command in the file menu Right clicking on the entry field allows for deleting a single entry The Packet Builder is an easy way to test the multipoint addressing mode of the WIT241x radio Since the WIT241x operates in a star configuration in multipoint mode only the base radio needs to address data to specific remotes All remotes send data back t...

Page 52: ...m any function or sequence of functions WinCOM can perform through a script file A script file is a text file that contains one or more commands and arguments save with a wcr filename extension Each command is separated by a carriage return and linefeed Configuration commands need to have wait periods between them The list of commands and their definitions is below ...

Page 53: ...d rate of the PC COM that WinCOM is using to 115 200 kbps de asserts DTR waits 200 milliseconds asserts DTR waits 200 milliseconds sends the configuration mode escape sequence waits 200 milliseconds and then sends the m command to the radio What this script file does is set the PC COM port baud rate to 115 2 kbps puts the radio in config mode and the issues the command to display all of the radio ...

Page 54: ... of a data file for transmission Navigate to a file then click Open and the file is transmitted immediately The Capture File dialog displays with a bar showing loading progression Once the file has finished transmitting the Final Average Throughput and Bytes sent numbers will be displayed ...

Page 55: ...Save to File which launches a Save As dialog that allows any data received to be loaded into a file After naming the file and clicking on OK the Capture Data window opens and shows the amount of data being received Clicking on Done stops the loading of received data into the file ...

Page 56: ...he base station s signal and also assert its DCD signal 4 Access modem control mode for each unit To access modem control mode use the F1 key to toggle DTR to 0 and back to 1 and then press the F3 key which sends the wit2400 escape sequence If you are not using WinCOM simply turn the radio off and back on and then type wit2400 must be lower case no backspace characters The transceiver should echo ...

Page 57: ...on zero link margin Carrier is detected but no data appears to be received Make sure that RTS is asserted to enable receive character flow In a point to point application if a remote is not receiving data check that the base s default handle is the same as the remote s In a multipoint application check that the remote is not configured for protocol mode and that the base is using the correct proto...

Page 58: ...aracters Check that the transmitted data can get through under these conditions Sometimes this symptom is caused by an application that is explicitly dependent on the timing of the received data stream The nature of the packetized RF channel imposes a degree of unpredictability in the end to end transmission delay Cannot communicate with the OEM module Make sure DTR and RTS are asserted DSR should...

Page 59: ...e required ETSI European Certification brETSI 300 328 no license required Rated RF Power 24 dBm Line of site Range approx 6 10 of a mile w 2dB dipole Frequency Range 2401 2495MHz Number of Channels 85 US Receiver Sensitivity 92dBm 10 5 BER Channel Data Rate 460Kbps IF Adjacent Channel Rejection 55dB 9 1 4 Mechanical Specifications Weight 28g Dimensions incl shield 69 85 x 47 75 x 4 57mm refer to s...

Page 60: ...necting to the WIT2450 make sure that all of the inputs TXD CFG RTS and SLEEP are terminated for proper operation 9 3 Approved Antennas The WIT2450 is designed to ensure that no antenna other than the one fitted shall be used with the device The end user must permanently affix the antenna by using an adhesive on the coupling such as Loctite or ensure the antenna has a unique coupling The table bel...

Page 61: ...WIT2450 2000 2005 Cirronet Inc 61 M 2450 0000 Rev B 9 4 Technical Support For technical support call Cirronet at 678 684 2000 between the hours of 8 30AM and 5 30PM Eastern Time ...

Page 62: ...WIT2450 2000 2005 Cirronet Inc 62 M 2450 0000 Rev B 9 5 Reference Design ...

Page 63: ...WIT2450 2000 2005 Cirronet Inc 63 M 2450 0000 Rev B 9 6 Mechanical Drawing WIT2450 ...

Page 64: ...nal to the goods such as but not limited to power failure No suit or action shall be brought against Seller more than twelve 12 months after the related cause of action has occurred Buyer has not relied and shall not rely on any oral representation regarding the goods sold hereunder and any oral representation shall not bind Seller and shall not be a part of any warranty THE PROVISIONS OF THE FORE...

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