MT Transcoder Series Master Development System

Editor Review

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Documentation Completeness and Clarity:

Hardware Completeness and Quality:

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Time to Complete

Prerequisite Skills

No special skills needed to use the kit. Some electronic and programming skills needed to create a design with the MT Transcoder chip. C-language experience needed later for external MCU control, but not mandatory for kit use.

What We Liked

 Easy to use.  Very good documents and manuals. Software examples helpful.  Good evaluation and test software that simplifies setup of chip functions.

What we Didn't Like

 Lack of some simple code or command-sequence examples.

Full Review

 I recommend this kit highly for engineers and product designers who need remote control or sensing of on-off devices. The hardware worked well and the software provides an excellent way to experiment with the boards. The boards required no special setup and worked right out of the box to demonstrate the transcoders' capabilities.  Linx has done a nice job with the hardware.

Introduction to the MT Transcoder

Linx Technologies created the MT Series Master Development System to highlight its MT Series Transcoder IC. So to start, here's a bit more information about this interesting and versatile device that engineers can use in many remote-control circuits. The chip provides eight digital I/O lines (D7--D0) that a designer can set in any combination of inputs or outputs. An input line, say D3, detects a logic one, usually from a switch or pushbutton, and signals an internal serial-interface engine to assemble a packet of information for transmission by an external RF transceiver chip or module. The transcoder has status and control lines that can turn on a transceiver, switch between transmit or receive, select a baud rate, and so on.

In a receiving unit, probably an appliance, security system, irrigation controller, home HVAC unit or similar device, an RF transceiver detects the transmission and routes the serial data into a transcoder chip.  The transcoder will output a logic one at the D3 pin to cause some type of local action.  In this case, the transmitting transcoder has set D3 as an input, and the receiving transcoder has D3 set as an output.  Both transcoders operate at the same serial bit rate and use a standard UART-type data stream, which makes them compatible with the serial ports on microcontrollers and other devices. And you can use infrared signaling instead of RF links.

The serial-interface engine (SIE) lets an external device, such as a  microcontroller, program internal transcoder registers and also read the contents of registers. To ensure secure communications, the chip provides for over 16 million addresses and its communication protocol allows for master-slave, peer-to-peer, or even rudimentary network configurations.  So, equipment designers can establish individual addresses for transcoders or they can let a transcoder accept all transmissions, regardless of address. A transcoder can "learn" as many as 60 addresses, so a product designer could create many combinations of transmitters and receivers. Each address combination can activate or deactivate any of the eight I/O lines.  Thus, a family with a keyless-entry lock system might let a teenager carry a transmitter that would let him or her operate the front-door lock but not the garage door or sprinkler system.

On to the kit...

The Linx MT Series Development System gives you two transceiver boards preset at the factory so each can control four corresponding LEDs on the other. In this way, each board acts like a transceiver.  A nine-volt battery powers each board, so you can test them without a connection to line power. During testing, the pushbuttons on one board controlled the LEDs on the other even at a distance of about 300 feet, with one board in my basement office and the other outdoors. The kit I received works in the 418-MHz ISM band.  Each board includes eight pushbuttons and eight LEDS, but I could have reconfigured the settings so, say, six pushbuttons on one board would control six LEDs on the other.  Each board also has two LEDs that indicate either receipt of a transmission or an acknowledgment reply from a transceiver.

Each board has a USB port that works with MT Master Development Software provided by Linx on a CD-ROM. In its Basic mode, the software demonstrates communications with a host PC via a virtual serial port on each device. An animated house shows the results from pushing buttons on a remote board.

The software also has an Advanced mode that lets designers select from 20 commands that send and receive packets of information. A read-local-settings packet, for example, returns the 24-bit address of the attached MT chip and the eight I/O configuration bits. A write-specific-user string sends the transcoder an address and the allowed output pins for that address. When you "mouse over" one of the commands, a set of bytes appear in hexadecimal format to show what the host PC will send. Then you can change the bytes highlighted in yellow. In this way, you can create commands and experiment with the boards. The software also displays the command sent and the response sent back by the transcoder.

The software was easy to use and designers will find it provides a good way to experiment with the boards. If they run into problems, they can choose to restore the factory-default configuration and get a fresh start.

A transcoder sends the information about input conditions for as long as at least one of the inputs provides a logic-one signal.  So, if you hold down one of the pushbuttons, the transmitter sends the pushbutton status information for as long as you hold it down.  Pressing a button doesn't cause just one transmission.

To further test the boards, I created a 4-bit binary counter with external hardware and applied the counter outputs to the four inputs on one of the boards.  The other board displayed the binary count, but as long as the four bits displayed a non-zero value, the transmitter continuously transmitted. (Actually, it transmitted and waited for an acknowledgment, transmitted again, and so on.)  During that test I walked about 300 feet from the counter setup and still observed counting.  Thus, if you needed to, you could send data from one point to another.  In this situation, an MCU might keep inputs to a transcoder at logic-zero, present the binary data to the transcoder for a set time, monitor for an acknowledgment response, and change the transcoder inputs back to zero. That process would stop additional transmissions of the same data and save power.

The transcoder also can operate with an 8-bit "custom value" entered through the IC's serial input in a command string and read at the receiver with a read-custom-date-value command packet.

The software was easy to use and I liked the display of command-packet data and the displayed results from the transcoder based on a command. I bet I could do some custom programming and have a basic remote control set up within a day or two.  I would recommend using the USB connection on each board tied to a separate computer running the Linx software as a good testbed or "breadboard" for communications so you can quickly assess what happens at each end and make any changes. They you could use an MCU to communicate with the transcoder on one board and use the other board with a PC to monitor operations and run tests.

The kit's User's Guide points to Application Note AN-00201, which covers installation of the USB drivers. The MT Series Transcoder Data Guide--basically a data sheet for the chip--refers to Application Note AN00157, "Connecting to the Serial Interface on the MT Series Transcoders."  Here you will find several C and VisualBasic program examples.

Linx could supplement the kit and documentation with several basic examples that start a newcomer with a simple project that lets one pushbutton on one board activate the corresponding LED on a remote board.  Just a list of the necessary command packets and the SIE packet values would do the job.  Then, the example could expand a step at a time in tutorial fashion to illustrate other capabilities.  The code examples provided look like all-in-one applications that could take some time to decipher.

The development boards provide easy access to the data signals and important status signals.  I connected my counter--created with an mbed MCU module I had on my bench--to the square I/O pins on the board with simple clip leads.  Several switches let you control on-board operations. And you can select the baud rate and a latch/no-latch mode on the transcoder. The User's Guide includes a set of clear schematics.

Key points:  The development boards include a Linx RF transceiver module (TRM-418-LT) that simplified communications. The USB connection relies on a Linx SDM-USB-QS controller and two other ICs to communicate with the transcoder chip. Your design might not need a USB port, though. The kit includes data sheets for the RF and USB devices. --Jon Titus

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