Operating Manual MHX-2400 2.4 GHz Spread Spectrum OEM Transceiver Revision 1.11, December 1, 2000 Microhard Systems Inc. #110, 1144 - 29th Ave. N.E. Calgary, Alberta T2E 7P1 Phone: (403) 248-0028 Fax: (403) 248-2762 www.microhardcorp.
MHX-2400 2.4 GHz Spread-Spectrum Embedded Modem WARNING In order to comply with the FCC/IC adopted RF exposure requirements, this transmitter system will be installed by the manufacturer's reseller professional. Installation of all antennas must be performed in a manner that will provide at least 20 cm clearance from the front radiating aperture, to any user or member of the public. This manual contains information of proprietary interest to Microhard Systems Inc.
Contents 1. 2. 3. A. B. C. D. E F. G. H. Introduction 1.0 Product Overview .............................................................................................................................................................................. 1 1.1 Features.............................................................................................................................................................................................. 1 1.2 About this Manual .............................
1. Introduction 1.0 Product Overview Congratulations on choosing the MHX-2400 wireless transceiver! Your new MHX-2400 modem is a state-of-the-art, 2.4 GHz frequency-hopping spreadspectrum communications module. When the MHX-2400 module is incorporated into the design of new or existing equipment, terminal devices (DTEs) up to 30 km (or more)1 apart will be capable of establishing highspeed2 communications wirelessly.
n 49 sets of user-selectable pseudo-random hopping patterns, intelligently designed to offer the possibility of separately operating multiple networks while providing security, reliability and high tolerance to interference; n encryption key with 65536 user-selectable values to maximize security and privacy of communications; n built-in CRC-16 error detection and auto re-transmit to provide 100% accuracy and reliability of data; n ease of installation and use – the MHX-2400 module uses a subset of standard
2. Initial Setup and Configuration 2.0 Unpacking and Inspection The following items should be found in the shipping carton. Inspect the contents for any shipping damage. Report damages or shortages to the distributor from which the unit was purchased. Keep all packing materials in the event that transportation is required in the future. Package contents (normal distribution): 1 MHX-2400 Wireless Modem module 1 2 Operating Manual (this document) 1 2.
Top View Vcc Vcc Vcc Vcc Vcc Vcc Vcc Radio Radio Logic Logic Logic Logic Logic N/C /CONFIG /RESET GND GND GND GND GND GND GND N/C N/C N/C 1 40 20 21 N/C N/C N/C N/C N/C N/C N/C Rx Mode LED Tx Mode LED RSSI LED 3 RSSI LED 2 RSSI LED 1 CTS RTS DSR N/C DTR TxD RxD DCD Antenna Connector Figure 1 - Pinout Diagram IMPORTANT: For best performance, it is strongly recommended to use a separate, linearly regulated supply for Vcc Radio. Do not directly feed a switching power supply into Vcc Radio.
Data Port (DCE) - Pins 21 through 28 inclusive. This port is used to interface the MHX-2400 module to a DTE device and operates at 2400 to 115,200 bps. The levels are active low 5V logic levels, and include (See Appendix B for a complete description): Pin No.
2.3 Configuration Prior to establishing a wireless link, each MHX-2400 module participating in the link must be correctly configured for compatibility and for the desired mode of operation. S M Network 1 R M Network topologies consisting of a single Master and virtually any combination of Slaves and Repeaters may be deployed.
How to Set Up A Simple Network The MHX-2400 will always be in one of two states: n Data Mode – When in this state, the modem is listening and talking to other modems in the network (the modem is online). n Command Mode – When in this state, the modem is awaiting “AT Commands” from the serial port. These commands are used to configure all operating parameters of the modem. When in this state, the modem is “offline”.
3. Configuration Options 3.0 Command Line Interface The MHX-2400 modem can be easily configured to meet a wide range of needs and applications. You can have your modem perform a variety of functions by sending it instructions (in the form of commands). Sending a command overrides the modem’s operating characteristics. Your modem must be in Command Mode for it to execute a command. If you send characters when the modem is in Data Mode, the modem transmits the characters over the air.
Note: If you want to send more than one command line, wait for a response before entering the AT prefix at the start of the next command line. To re-execute the previous command, enter A/. The modem will execute the previous command line. When in Command Mode, the modem “autobauds”, meaning that it will automatically adjust to the baud rate of the terminal. You may change the terminal baud rate while in Command Mode without losing communication with the modem.
O On-line Mode The O command attempts to put the modem online and communicate with a remote modem. Q Quiet Mode Your modem is preset to send responses when it executes commands, and there after to keep the host informed of its status. *Q0 Q1 V Enable modem responses Disable modem responses Result Codes display Your modem can either display result codes as words or numbers.
&F &F1 Master Load Factory Default Configuration The &F command resets the modem and loads the default factory configuration. &F2 &F1 Slave &F2 &F3 &F1 Master &F3 Repeater &F4 &F4 Slave &K Master Point-to-Multipoint. Designed to communicate with modems configured as &F2 or &F3. Slave. Designed to communicate with another modem configured as &F1. Repeater. Designed to communicate with modems configured as &F1 and &F4. Slave working with factory default Repeater and factory default Master.
3.2 Command Result Codes The MHX-2400 module can either display the results of a command as either text strings or numerical data. The following chart shows resulting text string and corresponding numeric result.
3.3 S Registers S Register 0 - Auto Answer If this register is set to zero, the modem will power up in command mode. If this register is non-zero, the modem will power up in data mode. S Registers 2 through 5 cannot be stored to nonvolatile memory. S Register 2 - Escape Code This register contains the ASCII value of the escape character. The default value (decimal 43) is equivalent to the ASCII character ‘+’.
S Register 101 - Operating Mode The Operating Mode (register S101) partly defines the “personality” of the MHX-2400 module. Allowable settings for this register are 1 through 4 as follows:. • • • • Only one Master can exist for each network.
3)Slave. Up to 65534 Slaves may exist in a network, all of which communicate with the common Master (either directly or via Repeater(s)). Slaves cannot directly communicate with other Slaves, nor can they acknowledge packets of data sent by the Master. Clearly this would cause conflicts when there are multiple Slaves. The Master does, however, send acknowledgements to all messages it receives from Slaves. The Master initiates communications by sending a broadcast message to all Slaves.
S Register 102 - Serial Baud Rate The Serial Baud Rate is the current speed that the modem is using to communicate with the DTE. When the AT command prefix is issued, the modem performs an ‘autobaud’ operation and determines what the current DTE baud rate is set to. The S register value returns the current setting of the DTE baud rate.
S Register 104 - Network Address Select a Network Address and assign it to all units which will be included in the network. The Network Address defines the membership to which individual units can be a part of. By establishing a network under a common Network Address, the network can be isolated from any other concurrently operating network. As well, the Network Address provides a measure of privacy and security.
the following diagrams illustrate the methodology for deploying simple to complicated networks: Master Slave Master Repeater Master Repeater1 M[1] ←→ S1[1] M[1] ←→ R1[1,2] ←→ S2[2] M[1] ←→ R1[1,2] ←→ R2[2,3] ←→ S3[3] M[1] ←→ R1[1,2] ←→ R2[2,3] ←→ R3[3,4] ←→ S4[4] Slave Repeater2 Slave It is reasonable to consider a Repeater as being both a Slave and a Master, alternating between Primary and Secondary Hopping Patterns as the unit changes channel.
S Register 107 - Encryption Key All units within a network must use the same encryption key. The Encryption Key provides a measure of security and privacy of communications by rendering the transmitted data useless without the correct key on the receiver. Valid Encryption Keys range from 0 to 65535. Keep in mind that all units within the network must use the same key for communications to succeed. S Register 108 - Output Power Level The Output Power Level determines at what power the MHX-2400 transmits.
IMPORTANT: FCC Regulations allow up to 36 dBi effective radiated power (ERP). Therefore, the sum of the transmitted power (in dBm), the cabling loss and the antenna gain cannot exceed 36 dBi. 1 mW = 0 dBm 10 mW = 10 dBm 100 mW = 20 dBm 1000 mW = 30 dBm For example, when transmitting 1 Watt (30 dBm), with cabling losses of 2 dB, the antenna gain cannot exceed 36 - 30 + 2 = 8 dBi. If an antenna with a gain higher than 8 dBi were to be used, the power setting must be adjusted appropriately.
S Register 111 - Packet Minimum Size S Register 112 - Packet Maximum Size S Register 116 - Packet Character Timeout These settings determine the conditions under which the modem will transmit accumulated data over the air. S Register 111 - Minimum Size Valid entries for this register are 1 to 255 bytes, which defines the minimum number of bytes to receive from the DTE before encapsulating them in a packet and transmitting over the air. The Minimum and Maximum Packet Size is controlled by the Master.
S Register 113 - Packet Retransmissions This register applies to both Master and Repeater operation. It does not apply to Slave operation. The Master will retransmit each data packet exactly the number of times defined by the Packet Retransmissions parameter. The Master retransmits once at the beginning of each hopping interval until the limit is reached. This parameter is not necessary in Slave units since all Slaves receive acknowledgement from the Master.
S Register 115 - Packet Repeat Interval A parameter that is specific to Slaves and Repeaters is the Packet Repeat Interval. The allowable settings are 1 through 255. The default is 1. This parameter defines a range of random numbers that the Slave will use as the next slot in which it will attempt to send the packet. For example, if this register is set to 7, the Slave will choose a number between one and seven as the next slot in which to transmit.
S Register 120 - RTS/DCD Framing S Register 121 - DCD Timeout The MHX-2400 supports two special types of data framing: • • Input (or RTS/CTS) Data Framing; and, Output (or DCD) Data Framing Input Data Framing is enabled by configuring the Handshaking Parameter as &K2. This type of framing makes use of the S120 parameter as illustrated in Figure 5. Parameter S120 can be set to any value between 0 and 254 ms.
MHX-2400 Operating Manual: Chapter 3 Configuration Options 25
A. Modem Command Summary The following provides a command summary for the MHX-2400 module. Factory settings are denoted with a ‘*’.
MHX-2400 Operating Manual: RS-232 Interface and Cables 27
B. Serial Interface The MHX-2400 module uses 8 pins on the header connector for asynchronous serial I/O. The interface conforms to standard RS-232 signals without level shifting, so direct connection to a host microprocessor is possible. The signals in the asynchronous serial interface are described below: DCD Data Carrier Detect - Output from Modem - When asserted (TTL low), DCD informs the DTE that a communications link has been established with another MHX-2400.
30 MHX-2400 Operating Manual: Appendix B Serial Interface
C. Sample Schematic Diagram The following is a sample microprocessor implementation with a MICROCHIP PIC 16C74 and the MHX-2400. The MHX2400 performs no level shifting on the serial port, so direct connection to the host microprocessor is possible. DO NOT CONNECT THE MHX-2400 TO RS 232 DRIVER OUTPUTS. DAMAGE TO THE UNIT MAY RESULT. On this implementation, the onboard SCI of the PIC 16C74 is directly connected pins 2 and 3 of the MHX-2400.
32 MHX-2400 Operating Manual: Appendix C Sample Schematic Diagram
D.
34 MHX-2400 Operating Manual: Appendix D Factory Default Settings
E. Performance Tables The scope of this appendix is to find the best possible performance and maximum packet size at different modes of operation. The setup assumes a baud rate of 115k, no retries and no retransmissions.. Slave to Master Communication. (No Repeater) Link Rate = Fast NO FEC Slave to Master Communication. (No Repeater) Link Rate = Fast WITH FEC Repeater to Master Direct Communication. Link Rate = Fast NO FEC Repeater to Master Direct Communication.
36 MHX-2400 Operating Manual: Appendix E.
F. Hopping Patterns This Appendix provides a guide for selecting appropriate hopping patterns (S106,S206). There are 49 hopping patterns: Patterns have been designed to notch out certain segments of the ISM band. Pattern Number Spectrum Used 0-7 2.4012 - 2.4824 GHz 8 - 10 2.4012 - 2.4312 GHz 11 - 13 2.4052 - 2.4352 GHz 14 - 16 2.4092 - 2.4392 GHz 17 - 19 2.4132 - 2.4432 GHz 20 - 22 2.4172 - 2.4472 GHz 23 - 25 2.4212 - 2.4512 GHz 26 - 28 2.4252 - 2.4552 GHz 29 - 31 2.4292 - 2.
38 MHX-2400 Operating Manual: Appendix F.
G. Technical Specifications Electrical/Physical Data Interface Asynchronous Serial Port, TTL Levels Signals Sig. Gnd, TX, RX, DCD, DSR, DTR, RTS, CTS Bandwidth / Data Rate 2,400 - 115,200 bps, uncompressed half-duplex, Approx. 100 kbps sustained in intelligent asymmetrical full-duplex transmission mode Communications Range1 30 kilometres (19 miles) Power Requirements 5 VDC, 1.0 Amp Power Consumption 700 mA max, 450 mA typical at 1W transmit; 200 mA receive Operating Frequency 2.4000 GHz to 2.
40 MHX-2400 Operating Manual: Appendix G.
H. Glossary Terminology Used in the MHX-2400 Operating Manual Asynchronous communications A method of telecommunications in which units of single bytes of data are sent separately and at an arbitrary time (not periodically or referenced to a clock). Bytes are “padded” with start and stop bits to distinguish each as a unit for the receiving end, which need not be synchronized with the sending terminal. Attenuation The loss of signal power through equipment, lines/cables, or other transmission devices.
can be controlled also by software using X-ON/XOFF (transmitter on/off) commands. Frequency-hopping A type of spread spectrum communication whereby the carrier frequency used between transmitter and receiver changes repeatedly in a synchronized fashion according to a specified algorithm or table. This minimizes unauthorized jamming (interference) and interception of telecommunications. Full-duplex Where data can be transmitted, simultaneously and independently, bidirectionally.
