A Detector Wireless Addressable Gas Detector with Two Way Communication
1 Application For detection of Gas and Heat
2 Voltage range 3.6 V/ 9VDC(Lithium battery)
3 Life of the battery Minimum 7 years
4 Standby current 20-30μA
5 Gas Detection LPG / LNG
6 Setting Resettable DIP Switch
7 Diiff. Alarm Output Different alarm output
8 Operating frequency 433.93 MHz.
9 Ambient temperature range -10deg C to +55deg C
10 Wireless Protocol Two Way Mesh /Multi-hop
11 Inbuilt Transreceiver Two Way Communication Module Mesh/Multi-hop RF Transceiver Module:

Frequency bands 433.05 – 433.92MHz
Number of channels 10
Data rate 1.2 – 100
Max output power 10 dBm
Sensitivity -110 dBm
Supply voltage 2.0 – 3.9 Volt
Current consumption,
RX / TX :24 / 35 mA
Current consumption,
SLEEP Typ. 0.3 uA
Temperature range -40 to +85
Coding : Infinite
Programmable at site
Modulation :FSK
Test Certificate : ERTL

12 Individual Data Transmission for
  1. Gas
  2. Dust accumulation
  3. Tamper /Detector Removal
  4. Low Bat
  5. Health Chk
13 Wireless Protocol Wireless MESH
14 Coverage Area 25 sq.mtr
15 Point Read:Handshaking principle A: Device status
B: Device type
C: Custom Device Label
D: Software Zone Label
E: Device Zone Assignments
F: All Program Parameters.
16 Handshaking The Detector  shall be in handshaking mode with the respective Hooter panel , Local Monitoring station . Handshaking for health condition to be communicated to the Hooter panel & Local CMS via two way communication with MESH protocol.

Health condition monitoring in each 01 hrx24 hrs of Local Monitoring Station/ Local Hooter Panel so that different Audio visual alarm with graphic presentation of Health condition monitoring of all the devices in Wireless FDA system install in Plant area in fixed intervals.
Low Bat, Detector Tamper, Dust accumulation chk monitoring shall be communicated using wireless two way communication MESH protocol to the local hooter panel /Local CMS


MESH Protocol

All addressable detectors, devices shall use MESH protocol with following specification & salient features:

Mesh conceptual description

Mesh is an all-embedded mesh/multi-hop network protocol which is fully embedded inside a family of RF modules with different RF frequency ranges. A network is defined to consist of a number of nodes where a node is one out of three types as described below. The wireless network of nodes can be connected to any type of sensors or actuators. The RF traffic is in a tree-type topology, where data transfer is up or down in the tree structure. The features fully contained in the embedded Mesh application firmware and which is dynamically and automatically handled after power up are:

  • Optimum network self forming
  • Self healing: The path with highest link quality and least number of hops to the recipient is chosen at any time. When optional paths are present, it is indicated with indicative blinks on a LED output. In a changing environment with changing link quality the network dynamically adapts to the optimum route

The features for wireless data transfer between any two nodes in the network are:

  • LBT (listen Before Talk)
  • Acknowledge
  • Retransmission(s) if required
  • AES128 encryption (optional)

Network Topology

The Mesh in its simplest topology consists of one Gateway and one Router. End nodes always must connect to a Router. There can be several Gateways within one network, they will then divide the work-load between them but there might be duplicate packages which must be handled at the end-server side.


Node description:

Gateway: Mandatory to form the network and as the name indicates, it takes the bidirectional application data to and from the wide area network or to a host processor which can be in the shape of a PC.

Router: Must be powered at all times as it takes the bidirectional data from any other device and in real-time either re-transmits and/or enter the application data on its UART.

End Device: Normally battery operated and normally in Sleep mode for increased battery lifetime. A host controller takes the End Device out of Sleep for transmitting data to the optimum Router location (automatically decided by Mesh).

Transparent mode and Packet mode

Default setting is transparent mode. In transparent mode, UART data entered into the Gateway will be received by all Routers in the network and will be made available at their UARTs without any changes. The addressing must then be in the application layer. In the other direction, with UART data from a Router to the Gateway, the data will only be

received by the Gateway without any changes. In Packet mode, addressed data is possible as well as individual I/O control and monitoring of each Router. The link will then not be transparent but will contain extra bytes for command and control. The Gateway can then ask for I/O read-back as well, and receive packet-path information.

Getting Started

Form a network by configuring at least one of the modules as Gateway. Then secure that all Routers and End Devices have different Unique IDs but same System ID. This is mandatory for successful network self forming.

How to form the network

Power up the nodes in any random sequence. The LEDs start to blink in a predefined pattern.. Each node invites neighboring nodes to become members of the network and contains a short-list of possible routing paths. When one or more Gateway(s) come into vicinity, and only then, the complete network forms. No extra external processing effort in the terms of a network organizer controller (PC or large microprocessor) is required, each node actively and autonomous participate in the forming of the RF network.

How to transmit data

This refers to the most easy-to-use mode, the default mode named “transparent” for transparent bidirectional data transfer.
The module will transmit the data when

  • the max packet length is reached
  • the modem timeout limit is reached

The timeout limit is configurable in-circuit.

How to  receive data

Any received data packet with correct address and check sum will be sent on the TXD of any Router(s) pin using the same UART format as for transmit.


A simple quarter wavelength wire or a PCB track antenna which should transmit & cover the proper range with length corresponding to the quarter of a wavelength.

Mesh™ Embedded Protocol

The module offers a buffered, embedded mesh protocol. All data to be sent is stored in the module before transmitted by the RF circuitry. Likewise, when data is received, data is stored in the module before sent to the host. This allows the communication controller to add address information and to do error check of the data.

Transparent mode operation

Serial data entered on the Gateway serial port will be delivered transparently to all connected Router devices and transmitted on their respective serial ports. Serial data entered on a Router or End device serial port will be delivered transparently to the Gateway and transmitted on the serial port. Regardless of device type (Gateway, Router or End device), the serial port UART is ready to receive data when CTS is true. RF transmission will automatically be triggered on buffer full or character time-out on the serial port. The connected host must always verify CTS is true before sending any character, or characters may be lost.

Packet mode operation

To Be Defined


A LED connected to this pin will flash with one of the following frequencies/intervals based on RSSI level to the best Router or Gateway which Mesh select:

  1. 4 seconds (2 seconds “on”, 2 seconds “off”): No connections (“I am alive” indication only)
  2. 2 seconds: RSSI within sensitivity level + 10 dB
  3. 0.5 seconds: RSSI > Signal level above criteria 2 above

Network connection/Redundancy indicator:

A LED connected to this pin will flash with one of the following intervals based on network connections:

  1. No light: No connections
  2. 2s intervals (1 second “on”, 1 second “off”): 1 alternative route on same level in tree structure
  3. 1s interval (0.5s “on” and 0.5 sec “off”): 2 or more alternative routes on level above in tree structure

In general, the higher the frequency on the indicators, the lower the packet loss rate will be and the more robust the network will be against changing conditions in each hop. Both outputs from the module can as well be monitored by an external processor for other visualization of RSSI level and network connection quality.

RF Frequency, Output Power Levels and Data Rates

The following table shows the available RF channels and their corresponding frequencies,nominal output power levels and available data rates.


RF Channel Output Power Data Rate
1: 433.100 MHz
2: 433.200 MHz
3: 433.300 MHz
4: 433.400 MHz
5: 433.500 MHz
6: 433.600 MHz
7: 433.700 MHz
8: 433.800 MHz
9: 433.900 MHz
10: 434.000 MHz
11: 434.100 MHz
12: 434.200 MHz
13: 434.300 MHz
14: 434.400 MHz
15: 434.500 MHz
16: 434.600 MHz
17: 434.700 MHz
1: -20 dBm
2: -10 dBm
3: 0 dBm
4: 5 dBm
5: 10 dBm
1: 1.2 kbit/s
2: 4.8 kbit/s
3: 19.0 kbit/s
4: 32.768 kbit/s
5: 76.8 kbit/s
6: 100 kbit/s
7: For future use

RSSI Reading

The RF module provides a digital Received Signal Strength Indicator (RSSI) through the ‘S’ command when in Configuration mode, and included in received messages when the Gateway module is operating in Packet Mode. The module returns an 8 bit character (one byte) indicating the current input signal strength (followed immediately by a second character which is the prompt (‘>’) when in command mode). The signal strength is used by the Mesh protocol to indicate fading margin, and as a carrier sense signal to avoid collisions. The signal strength measure by the S command is the instantaneous value. The RSSI value included in a received package, is the signal strength at the originating module, when receiving data from the module that has been selected as the first receiver of packets form the originating module i.e. the first jump in the mesh network.

The RSSI value increases with increased input signal strength in 0.5 dB steps. Input signal strength is given by (typ.):

P = – RSSI / 2 [dBm]

The dynamic range of the RSSI (P) goes from the Sensitivity level up to typical -30 dBm (RSSI saturation level).

Temperature Reading

The module provides readings of a digital temperature monitoring sensor (TEMP) through the ‘U’ command. The module returns an 8 bit character (one byte) indicating the current temperature in degrees Celsius (°C) followed immediately by a second character which is the prompt (‘>’). The TEMP value increases with increased temperature in 1 °C steps and accuracy of +/- 2 °C.

Temperature is given by:

T = TEMP(dec) – 128 [°C] (example: TEMP=0x98 equals +24 °C)

Power Supply voltage Reading

The module provides readings of an internal power supply voltage monitoring sensor (VCC) through the ‘V’ command. The module returns an 8 bit character (one byte) indicating the current power supply voltage level followed immediately by a second character which is the prompt (‘>’). The command can be useful for battery power monitoring. The VCC value increases with increased power supply voltage in 30 mV steps. The power supply

voltage is given by:

V = VCC(dec)*0.030 [V] (example: VCC=0x68 equals 3.12 V)

Module Configuration

The configuration of the module may be changed in-circuit from the host during operation, at the time of installation of the equipment, at the manufacturing test, or even as a standalone module. The configuration is changed by sending commands on the UART interface after the module is set in configuration mode. Configuration mode is entered by asserting the CONFIG pin (set low).

In configuration mode, the module will respond to commands by sending a ‘>’ prompt on the TXD pin. This indicates that the module is ready to receive new commands. The CONFIG pin may then be de-asserted. Note that the CONFIG pin must be de-asserted before the Exit command (‘X’) is sent to the module in order to return to normal operation.

After a command has been executed, the module responds with the ‘>’ prompt character, indicating it is ready for a new command. New commands must not be entered before the ‘>’ prompt has been received. The time required to execute a command may vary depending on the command (see the Timing Information section). There is no ‘>’ prompt after the ‘X’ exit command.