Wireless HART Adapter

WiWIZ1 HART MODEM MODULE FOR MULTIFUNCTIONAL HART ADAPTER


                                                                                            OEM HART modem

General Description

 

What is a wireless HART adapter?

 

There are approximately 20-30 million wired HART devices in the field. The HART standard allows for converting these units into wireless HART units. In order to accomplish this task a HART modem is attached to the wired HART device and then the wireless HART communicates with the HART modem to transmit the HART data over the wireless connection.


The HART modem module when added to the WiWiz1 allows the wireless unit to become a complete modem for HART(Highway Addressable Remote) in the master mode. It allows designers to easily implement a HART compliant modem as a master to attach to any HART compliant sensor device. The HART modem module requires only three controller I/O pins; transmit data (TXD), receive data (RXD), and request to send (RXD).

 

Power requirements are low enough to allow the modem to be powered directly from a microcontroller output pin. By connecting the voltage to a controller output pin, the modem can be effectively turned off, consuming zero power, when not being used. The module is a complete modem solution, including transformer isolation and capacitor coupling, eliminating grounding and polarity issues.

 

The carrier detect (CD) output provides indication that a HART signal is being received. When RTS is low, the modulator is selected. NRZ data to be Transmitted is shifted into the TXD pin at 1200 BAUD. The modem modulates the data using phase continuous frequency shift keying (FSK) at Bell 202 shift frequencies of 1200Hz and 2200Hz. The transmitted waveform is shaped to meet the slew rate requirements of the HART protocol. Received data is filtered, demodulated, and converted to NRZ data at 1200 BAUD, then shifted out on the RXD pin. A high logic level RTS enables the demodulator for receiving. RTS low enables the modulator for transmitting

 

 

Multi-Functional HART Adapter

 

Under normal circumstances the HART modem would be used in conjunction with the wireless HART communication stack which is available for the WiWIZ1. This configuration is not required. For example, the HART modem can be used in conjunction with any of the optional radio protocols such as ISA100, Zigbee or WiFi. One can create a HART adapter module that can transfer data from a HART sensor device over WiFi to an access point for eventual delivery directly to the Internet, PC or web server.

 

ATTENTION OEMs

 

For large volume applications a board level version of the HART modem is available. This option provides for substantially lower cost. Please note that the HART Modem can be used to convert a standard wired sensor device (4-20ma) into a wired HART device.

 

 

 

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