User's Manual

Waveport CF user manuel Coronis Systems
2.2 Format of exchanged frames
2.2.1 Wake-up and synchronization mechanism
Waveport CF normally stays in standby mode to optimize power consumption, waking up either:
• To poll for radio activity periodically
• When a serial frame is received from host equipment
In order to give the radio board time to wake up, a synchronization character is needed before the data in the
serial frame. This character is 0xFF in hexadecimal notation.
To be consistent, the radio board also precedes its frame transmissions with this synchronization character.
2.2.2 Frame description
The standard frame format is as follows:
SYNC STX LENGTH CMD DATA CRC ETX
1 byte 1 byte 1 byte 1 byte 0 - 250 bytes 2 bytes 1 byte
Sync.
character
Start of
transmission
character
Frame
length
Command Data
Control
Redundancy
Check
LSB First
End of
transmission
character
0xFF 0x02 0x03
LENGTH
• Minimum frame size is 6 bytes.
• Maximum frame size is 256 bytes.
• Frame length (byte LENGTH) is computed from its own position
through the included CRC. SYNC, STX, and ETX bytes are not
included in the length.
To ensure the integrity of information transmitted between the host and radio board, a 16-bit CRC code is
computed on overall frame data, not including STX and ETX characters (byte LENGTH is inserted in the
CRC).
The CRC code is computed by dividing the binary frame sequence by the following polynomial:
X16 + X12 + X5 + 1
Sample code for this is shown on the following page.
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