transfer of control and command information, it can also be used with
great success for the transfer of true variable data such as temperature,
pressure, or sensor data. However, the 260–470MHz band in which
the module operates is regulated by Part 15, Section 231 of the FCC
regulations. Many types of transmissions, especially those involving
automatic transmissions or variable data, may need to be periodic. You
may wish to review Application Notes AN-00125 and AN-00140 along
with Part 15, Section 231 of the FCC regulations for further details on
acceptable transmission content in the Unites States.
Another area of consideration is that of data structure or protocol. The data
should be formatted in a predictable way and should be able to deal
with errors due to interference. This will ensure that the data is received
and interpreted correctly. If you are not familiar with the considerations
for sending serial data in a wireless environment, you will want to review
Application Note AN-00160.
Protocol Guidelines
While many RF solutions impose data formatting and balancing
requirements, Linx RF modules do not encode or packetize the signal
content in any manner. The received signal will be affected by such factors
as noise, edge jitter, and interference, but it is not purposefully manipulated
or altered by the modules. This gives the designer tremendous flexibility for
protocol design and interface.
Despite this transparency and ease of use, it must be recognized that there
are distinct differences between a wired and a wireless environment. Issues
such as interference and contention must be understood and allowed for
in the design process. To learn more about protocol considerations, we
suggest you read Linx Application Note AN-00160.
Errors from interference or changing signal conditions can cause corruption
of the data packet, so it is generally wise to structure the data being sent
into small packets. This allows errors to be managed without affecting large
amounts of data. A simple checksum or CRC could be used for basic error
detection. Once an error is detected, the protocol designer may wish to
simply discard the corrupt data or implement a more sophisticated scheme
to correct it.
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