AN2707 Freescale Semiconductor / Motorola, AN2707 Datasheet - Page 5

• Manufacturer Part Number: AN2707
• Description: Software Drivers for Tango3 RF Transmitter and Romeo2 RF Receiver ICs
• Manufacturer: Freescale Semiconductor / Motorola

Sending Messages
With Header Detect
Sending Messages
Without Header
Detect
MOTOROLA
Key
Generated by driver
Supplied by application/programmer
RF Signal From Tango3
NOTE:
NOTE:
Preamble
Software Drivers for Tango3 RF Transmitter and Romeo2 RF Receiver ICs
Preamble, Header, Checksum and EOM are handled by the software drivers;
the application programmer does not have to specify these fields.
The Preamble and ID fields can be repeated.
Figure 2
that Romeo2 passes to the MCU using its SPI interface. Tango3 transmits a
Preamble then the ID field. When Romeo2 receives a valid ID, it will wait to
receive a Header field. When it receives a Header, it then expects to receive
Length, Data, Checksum and EOM fields. While waiting for the Header field, it
will ignore all other data. Note that its possible to have a delay between the ID
field and the next preamble and header fields.
Using this message format, Romeo3 does not pass the ID field to the MCU on
the SPI interface. It passes only the Length, Data and Checksum fields. This
reduces the load on the SPI interface.
It is also possible to repeat the Preamble and ID fields multiple times. This is
discussed below.
ID
The header field is used to determine the start of the Length field. Romeo2
transmits all data, received after the header field, on its SPI interface, typically
to an MCU. However, it is possible to send messages without using the header
field.
Tango3 transmits a message containing Preamble, ID, Length, Data,
Checksum and EOM fields. The ID field may be repeated to ensure that
Romeo2 detects the ID, if it is using its Strobe oscillator as discussed below in
Reducing Power Consumption on page 6
programmable in the software driver). Once Romeo2 has detected the ID field,
Figure 2. Message Format Using ID and Header
Freescale Semiconductor, Inc.
For More Information On This Product,
shows a message frame transmitted by Tango3 and the received data
Preamble
Go to: www.freescale.com
Header
Length
Length
Data0
Data0
………
………
(the number of repeats is
Data127
Data127
SPI output (Romeo2 to MCU)
Checksum
Checksum
EOM
Message Formats
AN2707
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