Description

The VT-DTMPA-485-433M module is designed as a wireless sub module for wireless communication between devices like controls, POS systems, data collectors etc. It offers several addressing modes and relieves the host systems of wireless-specific task such as checksum calculation, address resolution.

It can be deployed whenever the wireless exchange of data packet between two or more parties is required.

A RS485 interface whose data rate is adjusted flexibly is available for communicating with the host systems. The data rate can be adjusted from 2.4kbps to 115.2kbps.

Thanks to its small size and the external SMA antenna connector, the module can easily be installed in existing systems without any external circuits.

Key Features

GFSK modulation

Communication distance up to 1000 meter

 Supports addressing transparent communication

 Auto add preamble, checksum, address information

Supports setting mode to configure parameters Channel, Interface

Band Rate, Radio Data Rate, Output Power, Source Address,

Destination Address

 RS485 interface

 Half Duplex communication, 8N1 format

5.0V DC Power Supply

 Consumption: Transmit <250mA; Receive <55mA

 Optional Antenna

Application

 Automatic Meter Reading

 Wireless Sensor Network

 Data Collector

 Controls, Remote Controls

 POS Systems

 Building Automation

 Android Controls

Specification

Testing condition:Ta=25°C, VCC=5.0V

Parameter Value Condition/Note

Center Frequency 433MHz Programmable, up to 6 channels

Modulation GFSK Customize for ASK/FSK/OOK/MSK

Output Power Max: 25dBm Programmable, 0-25dBm

Sensitivity -110dBm 2.4kbps

Radio Data Rate Max 500kbps Programmable, 2.4-500kbps

RS485 Interface Rate Max 115.2kbps Programmable, 2.4-115.2kbps

Protocol Format 8N1 Customizable

Data Buffer Tow 100 bytes

Transmit Current <250mA Depend on output power

Receive Current <55mA

Distance 1000 meter Open area; Max output power; 2.4kbps Radio Date Rate

Operate Humidity 10%~90%

Operate Temperature -40℃~85℃

Input Voltage 5.0VDC±10% ±100mV

Antenna 50ohm

Size

Note:

1. Noted that higher radio data rate causes of shorter communication disdance.

2. Noted that higher radio data rate causes of lower sensitivity.

3. Noted that lower input voltage causes of lower output power.

4. Noted that the operate temperature out of range -40℃~85℃ will influence the center frequency.

5. Be sure to use a match antenna and mount it in the right way.

6. The environment will influence the communication disdance much.

Module Description

Device Type Description

Interface VCC Input Voltage DC5V±10%

GND GND Connect to the system GND

RESET Reset signal input TTL level, 10ms low level to reset the module

SLEEP Sleep Not available

A Serial port RS485-A(D+)

B Serial port RS485-B(D-)

SET Setting Not available

Reset Key RESET Signal Input Reset the module

Setting Switch Input Switch the module to work on setting mode

D1 LED1 Indicating the communicate state

D2 LED2 Indicating the communicate state

SMA connector Antenna Connect external antenna of 50ohm

Input Voltage

The input voltage of the module ranges from 4.5V to 5.5V. A clean supply voltage is needed for the module to function correctly.

Operating Modes

The device can be used in the following operating modes:

1. Transparent, Buffered data transceiver

2. Setting Mode

The operating mode can be selected by the setting switch state. If the setting switch keeps on the “SET” state, the module will run on the setting operating mode after power up. Otherwise, if the setting switch keeps on the “TRANSPARENT” state, the module will run on the transparent operating mode after power up. The setting switch state shows as Fig 1.

Fig 1 Switch States

Transparent Mode

In this operating mode, data of the transmitter module is received via the RS485 interface and initially buffered. As soon as specific conditions are met (timeout or data buffer be filled full), the radio telegram is generated with preamble, Sync word, and Checksum and address information (modules address are the same). As soon as the transmission of a packet has begun, the RS485 interface cannot receive any further data.

The receiver module receives the wireless telegram and transmits the payload characters via RS485 interface. As long as receiver module is busy in sending characters via the RS485 interface, wireless telegram reception is not possible. For example, this effect is noticeable when sending a long data packet and subsequently a short data packet. In this case, the receiver module may still be busy in sending the first packet via RS485 interface and the second packet may be lost.

Setting Mode

This operation mode primary serves module configuration parameters.

In this operating mode, there are menus to guide the setting commands and configuration parameters. In order to setting the module, use a RS485 to RS232 Bridge to connect the module to a PC and be sure to install a com assistant like Commassistant, Terminal etc. We will offer the Terminal com assistant.

The configuration parameters are saving to the on-chip flash after access the exit command. The configuration parameters take affect after reset the module when exit the setting mode. The setting commands and configuration parameters show on the Tab 1.

Tab 1 Setting Commands and Configuration Parameters

Commands Command Function Configuration Parameters

U Setting the RS485 interface band rate 1 - 2400 bps

2 - 9600 bps (Default)

3 - 19200 bps

4 - 38400 bps

5 - 57600 bps

6 - 115200 bps

D Setting the radio data rate 1 - 2400 bps

2 - 9600 bps

3 - 19200 bps

4 - 38400 bps

5 - 250000 bps (Default)

6 - 500000 bps

C Setting the channel 1 - Ch=1 - 430 MHz

2 - Ch=2 - 431 MHz

3 - Ch=3 - 432 MHz

4 - Ch=4 - 433 MHz (Default)

5 - Ch=5 - 434 MHz

6 - Ch=6 - 435 MHz

P Setting the output power 1 - -10 dBm

2 - -5 dBm

3 - 0 dBm

4 - +5 dBm

5 - +7 dBm

6 - +10 dBm (Default)

S Setting source address Address ranges from 0x00 to 0xFF (Default 0xFF)

E Setting destination address Address ranges from 0x00 to 0xFF (Default 0xFF)

X Exit setting mode The configuration parameters be save to the on-chip flash after access this exit command

The RS485 interface band rate is configured to 9600bps in the setting mode. For example, to set the radio data rate to 500kpbs, the setting steps are:

1. Connect the module to a computer via RS485 to RS232 Bridge.

2. Run the com assistant Terminal and select the right COM Port, band rate set to 9600bps, 8N1 format.

3. Switch the setting switch to the “SET” state and reset the module. Setting menu display on the Terminal.

4. Enter “D” command and send. A radio data rate list display on the Terminal.

5. Enter “6” and send to select the 500kbps radio data rate.

6. Enter “X” command to exit setting mode. Parameter configures success.

From Fig 3 to Fig 6 show the configuration process.

Fig 2 Commands Menu Fig 3 Radio Data Rate List

Fig 4 Select the 500kpbs Fig 5 Exit Setting Mode

Addressing

Addressing is available. The transmission module generated the Source Address and the Destination Address information to the wireless telegram. The receiving module will only deliver the data to the host system via RS485 interface if both the destination address and source address correspond to the source addresses and the destination address itself.

Start-up

In the factory state, the modules are immediately ready for operation. Default in transparent operating mode. The default parameters are:

 RS485 interface Band Rate: 9.6kbps

Radio Data Rate: 250kbps

 Channel: 433MHz

 Output Power: +10dBm

 Source Address: 0xFF

Destination Address: 0xFF

Module is connected to a PC via RS485 to RS232 Bridge. Run a com assistant such as Terminal. Select the Port and default parameters. Enter the data to be sent like “V-chip Microsystems,Inc” and send. The receiver receives this data packet. LEDs flash while communicating in both transmitter and receiver. When transmitting large amounts of data, the limited buffer size in the module must be taken into consideration. The data can only be transmitted packet by packet.

Fig 6 Transmission Fig 7 Reception

Notes

1. Telegram Delay Time

There are hundreds of millisecond delay time for a telegram between transmission and reception. The accurate delay time depends on the RS485 interface band rate, radio data rate and the packet size.

2. Control Errors

For every telegram has CRC checksum, it is reliable communication in short distance communicating. But this is not enough in severe environment. In order to improve the reliability of communication, it is necessary to use ARQ protocol in the host.

3. Large Amounts of Data Transmission

There are two individual data buffers for buffering data from host before transmission via wireless. Each buffer size is 100 byte. Actually, for large amounts of data transmission, the data can only be transmitted packet by packet. The packet size is 100 byte.

4. Networking Application

Using the addressing functionality, it is available to establish peer to peer, peer to multi-peer protocol. In the case of peer to multi-peer application, the basic device can receive all end devices’ telegram and delivery data to its host via the RS485 interface. The entire end devices can receive the basic device’s telegram and delivery data to its own host via the RS485 interface.

If there are many pairs used in the same range area, it is necessary to use different channel between pairs to avoid co-channel interference.

Dimensions

Antennas

We offer many kinds of antennas. We can design a matching antenna for specific conditions. Some of the antennas are show on the Tab 2.

Tab 2 Antennas

Spring Antenna

Small size

Low cost

 Easy to embedded

SMA Plastic Antenna

 Medium size

 Low cost

 High gain

Sucker Antenna

High gain

 Have sucker

Easy to fix

Troubles and Processing Methods

Troubles Processing Methods

Short distance 1. Check the input voltage; ensure it is not lower than 4.5VDC.

2. Configure the output power parameter to the max.

3. Check the antenna; ensure it is not to be shielded.

4. Configure the radio data rate to a lower value.

Communicating failed 1. Check the input voltage.

2. Reconnect the module to the host.

3. Addresses of the communicating modules are all right.

4. LEDs flash while transmission or reception.

High error rate 1. Antenna does not match to the module.

2. Co-Channel interference, try another channel.

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