Communication Concept
AN2707. For more information on configuring the device drivers to allow communication between Tango,
Romeo, and Echo devices, see Section 14, “Communicating with Romeo2 and Tango3 Devices.”
The driver is supplied as two software files—Echo.C and Echo.H. Configure the driver by making
selections in the Echo.H file.
Features of the driver include:
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Configurable statically for modulation type, frequency band, data rate, device ID, and header
Supports bank switching—communicating on two RF channels
Transmits and receives variable length messages with up to 127 bytes data
Automatic checksum based error detection for each message
Controls receiver on/off cycling using Echo’s internal strobe oscillator or directly via an I/O pin
Provides dynamic control of the precise frequencies used in the selected band
Provides dynamic control of Tx power and Rx sensitivity
Supports received signal strength indicator (RSSI) measurement during message reception
Compatible with Tango3/Romeo2 communications
Compatible with 8-bit Freescale MCU families HC08 and HCS08
For more information, refer to the Echo device data sheet (available at http://www.freescale.com ).
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Communication Concept
Echo can support communication in the 304 MHz, 315 MHz, 434 MHz, 868 MHz, and 916 MHz bands
with data rates up to 22 kbps. Within each frequency band, you can choose the local oscillator and carrier
frequencies used.
Multiple transmitters (Tango3), receivers (Romeo2), and transceivers (Echo) may be present in a network
and can be individually selected by assigning each receiving device a unique ID. Groups of devices may
be formed by assigning a number of devices the same ID, supporting multicast or broadcast
communication.
Echo devices can be used in applications requiring two-way communication or flexible allocation of
transmitter and receiver roles, which can be changed dynamically. Public key and certification
authentication schemes are examples of applications that demand two-way communication.
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Message Format
The driver supports sending messages in two formats that differ in the way that the ID is sent: spaced
preamble/ID sequences followed by the message or repeated consecutive IDs, with no spacing, followed
by the message. The driver also supports tone signaling: the application may use the ID repeat mode with
an ID of all 1 or all 0. These formats are shown in Figure 1.
Software Drivers for MC33696, Rev. 1
2
Freescale Semiconductor
FREESCALE [ Freescale ]
