User's Manual

Table Of Contents

MReX Transceiver User Manual v1.92 Firmware

Serial Point to Point Operation

The MReX is well suited for use as a wireless point to point serial link.

In this application, the RAW protocol is used with a transport format that allows any ASCII charac-

ter to be transmitted. Raw serial data in any format presented to the MReX is transmitted across the

air and is output from a remote MReX. The behaviour of this feature is the same as if a serial wire

cable would be fitted between the units.

A typical application for this feature would be the writing information to remote LED signs. The

MReX can write to many remote units simultaneously.

In order to transmit serial characters, the MReX needs to be configured to know which ASCII char-

acter should be used to invoke an immediate transmission (or if any), the maximum number of

serial characters to transmit at any time and how long after a period of inactivity any buffered data

should be transmitted.

The rate that data is transmitted across the air varies based on application. Typically, slower over

the air transmitted rates such as 1200 or 2400 will result in higher sensitivity of the receiver, making

the possible distance between each MReX greater. By default the transmission baud rate is 4800.

Data transmitted over the air has bit error correction included to improve immunity to noise.

The MReX will typically allow up to 300 characters to be transmitted at a time, with buffering cap-

ability to allow several messages of this length to be queued for rapid transmission.

If the buffering capacity of the MReX is exceeded then the MReX will respond with “FULL<CR>”.

Prior to each transmission the channel checks if the MReX is clear to transmit, meaning that in

some cases transmissions could be slower depending on channel usage.

The MReX uses the default CAP code to identify each transmission, meaning that the MReX can

either transmit to one or many other MReX units addressed individually or multicast to many at

once.

The data transport method used includes bit error correction information, that allows for a more ro-

bust system, but decreases the effective data rate. Any over the air transmission rate will effectively

be halved due to the additional bit correction data that is also transmitted.