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Related Manuals for Microhard Systems MHX-920
Summary of Contents for Microhard Systems MHX-920
- Page 1 Operating Manual MHX-920 900 MHz Spread Spectrum OEM Transceiver Revision 1.20, December 21, 2000 Microhard Systems Inc. #110, 1144 - 29 Ave. N.E. Calgary, Alberta T2E 7P1 Phone: (403) 248-0028 Fax: (403) 248-2762 www.microhardcorp.com...
- Page 2 This manual contains information of proprietary interest to Microhard Systems Inc. It has been supplied in confidence to purchasers and users of the MHX-920, and by accepting this 900 MHz material the recipient agrees that the contents will not be copied...
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Page 3: Table Of Contents
S Register 213 - Packet Retry Limit..............................31 S Register 115 - Packet Repeat Interval............................31 S Register 117 - Modbus Mode ................................ 32 S Register 118 - Roaming ................................. 33 S Register 119 - Quick Enter to Command............................33 MHX-920 Operating Manual... - Page 4 5.2.2 Installing External Cables, Antennas and Lightning Arrestors......................42 Modem Command Summary ..................................45 Serial Interface ......................................47 Sample Schematic Diagram ..................................49 Factory Default Settings....................................51 Performance Tables...................................... 53 Hopping Tables......................................55 Technical Specifications ..................................... 57 Mechanical Drawing....................................59 Glossary ........................................61 MHX-920 Operating Manual...
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Page 5: Introduction
Remote Camera/Robot Control; n Security Systems; and, n Display Signs. While a pair of MHX-920 modules can link two terminal devices (“point-to- point” operation), multiple modules can be used together to create a network of various topologies, including “point-to-multipoint” and “repeater”... -
Page 6: About This Manual
AT style commands, very similar to those used by traditional telephone line modems. While the typical application for the MHX-920 is to provide a short- to mid- range wireless communications link between DTEs, it can be adapted to almost any situation where an asynchronous serial interface is used and data intercommunication is required. -
Page 7: Electrical/Physical
2.0 Functional Block Diagram DVcc AVcc Mixer Antenna IF Demod Switch Frequency Synthesizer Comparator Mixer GAIN RSSI1-3 \Config \Reset RXMODE TXMODE SRAM SRAM EEPROM 8 bit data bus UART (DCE) Figure 1. Functional Block Diagram MHX-920 Operating Manual: Chapter 2 Electrical/Physical... -
Page 8: Pinout
2.1 Pinout Figure 2 provides a top-view pinout drawing of the MHX-920 module. The corner pins (1,20,21,40) are labeled directly on the module. AVcc AVcc DVcc DVcc DVcc DVcc DVcc Rx/SYNC MHX-910 \Config TxMODE \Reset RSSI3 RSSI2 RSSI1 Figure 2 - Pinout (Top View) Table 1. - Page 9 RX/SYNC Active high output indicates receive and synchronization status. See Section 2.2. RS-232 Transmit Data. TTL level input. TXMODE Active high output indicates module is transmitting data over the RF channel. See Section 2.2. MHX-920 Operating Manual: Chapter 2 Electrical/Physical...
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Page 10: Led Operation
Repeater or Master with which it communicates See Table 3 *If Slaves have been silent for 2 seconds, repeater will base its RSSI on packets received from the Master. MHX-920 Operating Manual: Chapter 2 Electrical/Physical... - Page 11 Signal Strength (dBm) RSSI1 RSSI2 RSSI3 -108 50% duty cycle -101 on solid on solid 50% duty cycle on solid on solid on solid on solid 50% duty cycle on solid on solid on solid MHX-920 Operating Manual: Chapter 2 Electrical/Physical...
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Page 12: Dc Characteristics
Output Low Voltage (Pins 21,22,26,28- Output High Voltage (Pins 21,22,26,28- Sourcing Current (Pins 21,22,26,28-33) SRCE Caution: Using any other power supply which does not provide the proper voltage or current could damage the MHX-920 module. MHX-920 Operating Manual: Chapter 2 Electrical/Physical... -
Page 13: Ac Characteristics
A fixed internal reset delay timer of roughly 500ms is triggered as the V or V threshold is reached. \Reset Internal Reset TOUT Data Mode (Valid when S0=1) Command Mode (Valid when S0=0) Figure 3. Reset Timing MHX-920 Operating Manual: Chapter 2 Electrical/Physical... - Page 14 MHX-920 Operating Manual: Chapter 3 Modes of Operation...
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Page 15: Modes Of Operation
920 is a frequency hopping transceiver, meaning that it “hops” to a new frequency after a predetermined time interval. This time interval is a fixed time set by the user, and can range from 8ms to 120ms. The MHX-920 hops according to a pseudorandom pattern of 50 different channels. -
Page 16: Command Mode
3.2 Command Mode Network 3 The MHX-920 firmware has been designed to allow the user to customize the operation of the modem through an AT Command Interface. This interface is ideal for direct interface with another microcontroller or for higher level Windows-based software applications, but also contains user-friendly built-in register descriptions. -
Page 17: At Command Interface
S114=0 Remote Control S122=0 The MHX-920 is controlled through an AT Command line interface using a command set which is very similar to a traditional Hayes telephone modem command set. All line entries must be preceded by the characters ‘AT’. The characters ‘AT’... - Page 18 DTE equipment to which it is connected. Therefore, when in command mode, you may change the baud rate of your equipment, and the MHX-920 will automatically adjust to this baud rate once an AT string is POWER-UP...
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Page 19: Configuration
4. Configuration This chapter provides a detailed description of the various operating parameters of the MHX-920. Section 4.1 provides a quick-start approach which outlines the minimum requirements for establishing communication between two MHX-920 modules. The settings will not necessarily provide optimal performance for your application, but will verify that the modules are functioning correctly. -
Page 20: At Commands
&W is issued to store the current configuration into non-volatile memory. Settings are retained even after powering down. All user selectable parameters for the MHX-920 are described in detail in Sections 4.2 and 4.3: Checking the Link To check if the units are communicating, observe the LED indicators on the development board which houses the Slave unit. -
Page 21: A Answer
Enable modem responses Disable modem responses Result Codes display Your modem can either display result codes as words or numbers. Display Result Codes as numbers Display Result Codes as words MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 22: W Connection Result
&F3. &K Handshaking The &K command controls the handshaking between the modem and host microprocessor. &K0 Disable handshaking &K2 RTS/CTS input data framing. See page 33 for details. *&K3 Enable hardware handshaking (RTS/CTS) MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 23: Sdsr (Data Set Ready)
This command causes the modem to display the current setting of S register xxx. Sxxx=yyy Set S register value (see section 4.3 S-Registers) This command sets the specified S register to a value specified by yyy. MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 24: Command Result Codes
AT Command Result Codes The MHX-920 module can display the results of a command as either text strings or numerical data. The following chart shows resulting text string and corresponding numeric result. NO CARRIER ERROR CONNECT 2400 CONNECT 3600 CONNECT 4800... -
Page 25: S Registers
This register cannot be stored to non-volatile memory. If the modem is reset, or powered down, the default value is restored. Default is ‘BS’ (decimal 8). MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 26: S Register 101 - Operating Mode
S Register 101 - Operating Mode The Operating Mode (register S101) partly defines the “personality” of the MHX-920 module. Allowable settings for this register are 1 through 5 as Only one Master can exist follows:. for each network. • S101=1 Master Point to Multipoint •... - Page 27 Figure 8 - A Network Utilizing Three Hopping Patterns If there is no DTE connected to the Repeater, turn off handshaking (&K0) and set the baud rate to 115K. MHX-920 Operating Manual: Chapter 4 Configuration...
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Page 28: S Register 102 - Serial Baud Rate
DTE equipment to which it is connected. Therefore, when in command mode, you may change the baud rate of your equipment, and the MHX-920 will automatically adjust to this baud rate once an AT string is issued. The new baud rate is stored in register S102. -
Page 29: S Register 104 - Network Address
S Register 106 - Primary Hopping Pattern S Register 206 - Secondary Hopping Pattern Since the MHX-920 is a frequency-hopping modem, the carrier frequency changes periodically according to one of 64 pseudo-random patterns, defined by the Primary and Secondary Hopping Patterns. Valid entries for each are 0 through 63. - Page 30 However, if the units are far enough away from one another, hopping patterns may be reused in different sections of the network, without causing interference. MHX-920 Operating Manual: Chapter 4 Configuration...
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Page 31: S Register 107 - Encryption Key
S Register 108 - Output Power Level before deploying the network. The Output Power Level determines at what power the MHX-920 transmits. The MHX-920’s sensitive receiver can operate with very low power levels, so it is recommended that the lowest power necessary is used; using excessive power contributes to unnecessary “RF pollution”. -
Page 32: S Register 109 - Hopping Interval
36 - 30 = 6 dBi. If an antenna with a gain higher than 6 dBi were to be used, the power setting must be adjusted appropriately. Microhard Systems Inc. limits the MHX-920’s transmitted power to 100mW for all units purchased with antennas with gain above 6dBi. -
Page 33: S Register 110 - Data Format
Repeater or Slave will ignore its own S112 register and abide by the Master’s S112 setting. If S114=1 at any particular Repeater or Slave, that Repeater or Slave will use its own local S112 setting. The default for S112 is 255 bytes. MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 34: S Register 113 - Packet Retransmissions
After which, if the timer detects a gap in the data exceeding the Packet Character Timeout value, the modem will transmit the data. The MHX-920 will accumulate data in its buffers from the DTE until one of the following requirements is met (whichever occurs first): •... -
Page 35: S Register 213 - Packet Retry Limit
1 to have the Slave transmit in the first available slot. Choose higher intervals for less frequent transmission, or to avoid collisions between many Slaves in the system. This register is always disregarded and taken as S115=1 in Point-to-Point mode. MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 36: S Register 117 - Modbus Mode
Modbus Mode allows for the MHX-920 to be fully Modbus compatible. For Modbus operation, the general requirement is to get the packet of data to the receiving serial port with no gaps in the data. The MHX-920 incorporates a “Modbus Mode” which implements a delay at the receiving modem to ensure that no gaps are introduced. -
Page 37: S Register 118 - Roaming
Data Mode. The default setting is 1 - Enabled. S Register 120 - RTS/DCD Framing S Register 121 - DCD Timeout The MHX-920 supports two special types of data framing: • Input (or RTS/CTS) Data Framing; and, •... -
Page 38: S Register 122 - Remote Control
This register displays the average signal strength in dBm over the previous four hop intervals. The value in this register is also reflected in status lines RSSI1,2 and 3. See Section 2.2 for a description of RSSI, and how it is derived. MHX-920 Operating Manual: Chapter 4 Configuration... -
Page 39: Diagnostics, Statistics And Remote Control
# of Slave's sync errors = 0 # of CRC errors = 0 The MHX-920 starts the statistics count at zero each time the unit is powered up, or after the ATP command has been issued. By entering the ATP command, all statistics are cleared back to zero. The maximum limit for each statistic is 65535. -
Page 40: Remote Control And Diagnostics
‘x’ changes the corresponding remote’s register to ‘x’. Remember, any changes you wish to retain in the event of a powerdown or reset should be stored to non-volatile memory by issuing the write command ‘e’. MHX-920 Operating Manual: Chapter 4 Configuration... - Page 41 Read # of CRC errors k255 statistics Clear statistics l(x) S119 Quick Enter to Command Mode m(x) S118 Roaming n(x) S114 Packet Size Control o(x) S111 Min Packet Size p(x) S112 Max Packet Size MHX-920 Operating Manual: Chapter 4 Configuration...
- Page 42 Table 5. Table 5 - Master Diagnostics Commands Command Master Register Description r(x) S105 Unit Address S101 back to normal operating mode t(x) S109 Hopping Interval u(x) S104 Network Address v(x) S106 Hopping Pattern MHX-920 Operating Manual: Chapter 4 Configuration...
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Page 43: Installation
The installation, removal or maintenance of all The MHX-920 complies with FCC part 15 at the modular level for antenna components must operation in the license-free 902-928 MHz ISM band. This chapter... - Page 44 The minimum strength for communication is roughly -105 dBm. For consistent reliable communication, you should try to deploy the equipment such that signal strength exceeds -95 dBm. MHX-920 Operating Manual: Chapter 5 Installation...
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Page 45: Antennas And Cabling
5.2 Antennas and Cabling This section describes the recommended procedure for installing cabling and antennas for use with the MHX-920 module. 5.2.1 Internal Cabling The most common method for installing the module is to run a cable from the module’s MCX connector to a reverse TNC bulkhead connector on the chassis of the equipment as shown in Figure 11. -
Page 46: Installing External Cables, Antennas And Lightning Arrestors
Direct human contact with the antenna is potentially unhealthy when the by qualified and experienced MHX-920 is generating RF energy. Always ensure that the MHX-920 personnel. equipment is powered down during installation. Surge Arrestors... - Page 47 Omni-directional antenna with appropriate gain. The Effective Radiated Power (ERP) emitted from the antenna cannot exceed +36 dBm ERP. With the MHX-920 set to full power, ERP is calculated as follows: To comply with FCC regulations, .you must limit ERP to 36 dBm or ERP = 30 - (Cabling and Connector Losses) + (Antenna Gain) <...
- Page 48 MHX-920 Operating Manual: Chapter 5 Installation...
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Page 49: Modem Command Summary
A. Modem Command Summary The following provides a command summary for the MHX-920 module. Factory settings are denoted with a ‘*’. AT Commands S Registers Auto Answer Answer 0 = power up in Command Mode, Command Echo *1 = power up in Data Mode E0 No Echo Escape code [0...255] default ‘+’... - Page 50 MHX-920 Operating Manual: Appendix A Modem Command Summary...
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Page 51: Serial Interface
B. Serial Interface The MHX-920 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:... - Page 52 MHX-920 Operating Manual: Appendix B Serial Interface...
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Page 53: Sample Schematic Diagram
DO NOT CONNECT THE MHX-920 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-920. The bi- directional Port D is used for asserting or monitoring control signals from the MHX-920. - Page 54 MHX-920 Operating Manual: Appendix C Sample Schematic Diagram...
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Page 55: Factory Default Settings
DCD Timeout (ms) S121=0 DCD Timeout (ms) S121=0 Remote Control S122=0 Remote Control S122=0 Secondary Hop Pattern S206=2 (Don’t Care) Secondary Hop Pattern S206=2 (Don’t Care) Packet Retry Limit S213=2 Packet Retry Limit S213=2 MHX-920 Operating Manual: Appendix D. Factory Default Settings... - Page 56 MHX-920 Operating Manual: Appendix D Factory Default Settings...
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Page 57: Performance Tables
1 (8 ms) Slave <--> Master 2 (12 ms) Through One or 3 (16 ms) More Repeaters. 4 (20 ms) 5 (30 ms) Link Rate 6 (45 ms) S103=4 7 (80 ms) 8 (120 ms) MHX-920 Operating Manual: Appendix E. Performance Tables... - Page 58 MHX-920 Operating Manual: Appendix E. Performance Tables...
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Page 59: Hopping Tables
Each pattern must use a channel only once, and must consist of exactly 50 channels. There are 127 channels available ranging from Channel 1 at 902.4 MHz up to Channel 127 at 927.6 MHz. MHX-920 Operating Manual: Appendix F. Hopping Patterns... - Page 60 MHX-920 Operating Manual: Appendix F. Hopping Patterns...
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Page 61: Technical Specifications
Encl: 3.5” x 2.1” x 1.” (90 mm x 53 mm x 25 mm) Dimensions (LxWxH) Weight 75 grams Operating Environment Temperature: -40 to +70°C Humidity: 5 to 95%, non-condensing Storage Temperature -40 to 90°C 1. Clear line-of-sight, elevated high-gain antennas. MHX-920 Operating Manual: Appendix G. Technical Specifications... - Page 62 MHX-920 Operating Manual: Appendix H. Mechanical Drawings...
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Page 63: Mechanical Drawing
H. Mechanical Drawing MHX-920 Operating Manual: Appendix H. Mechanical Drawing... - Page 64 MHX-920 Operating Manual: Appendix H. Mechanical Drawings...
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Page 65: Glossary
I. Glossary Terminology Used in the MHX-920 Operating Manual Asynchronous communications receiving end, a similar algorithm is performed A method of and checked against the transmitted checksum. telecommunications in which units of single bytes of data are sent separately and at an arbitrary time... - Page 66 (Recommended Standard 232; more accurately, RS-232C or EIA/TIA-232E) Defined by the EIA, a widely known standard electrical and physical interface for linking DCEs and DTEs for serial data communications. Traditionally specifies a 25-pin D-sub connector, although MHX-920 Operating Manual: Appendix I . Glossary...
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