Linx NT Series Reference Manual

NT Series Transceiver Wireless UART
Reference Guide RG-00102

Introduction

The NT Series transceiver's transparent data pipe is ideal for applications
that use custom protocols or legacy protocols such as PWM that are not
compatible with a standard transmission format. However, the NT Series
also has an internal packet generator for applications that don't need a
custom protocol and don't have the time or warrant the effort of creating
a protocol.
The packet generator takes the data presented by the user and combines
it with a preamble, SYNC word and a CRC value to create a packet. This
packet is suitable for transmission in the noisy RF environment. On the
receiving side, the packet generator validates the received packets and
presents the received data to the user if the packets arrived intact.
The internal packet generator is accessed through the module's
Command Data Interface (CDI). The CDI is a standard UART interface
that is compatible with UARTs in a wide variety of off-the-shelf
microcontrollers. The standard UART data structure is not robust enough
for the noisy RF environment, so a protocol is required to protect the data
and ensure that it is received correctly. The module's UART interface and
internal packet generator combine to create a wireless UART and allow
the designer to bypass protocol development.

Packet Mode Data Structure

Figure 1 shows the packet structure used by the NT Series.
8 Bytes 3 Bytes
Preamble SYNC Word
Figure 1: NT Series Transceiver Packet Mode Data Structure
The preamble is used to "clear the pipe." It is a repeating pattern
(typically 101010) that can be distinguished from random noise. It allows
the receiver circuitry to lock on to the signal and center itself without
sacrificing any data.
The SYNC word is a fixed pattern of 3 bytes that identifies the packet as
belonging to the system and allows the receiver to synchronize to the
incoming data. It must match what is expected or the packet is
rejected.
1 to 96 Bytes 2 Bytes
Payload CRC
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