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Q: FAQ: Customizing [PREAMBLE+SYNC] patterns/lengths in CC110x/CC111x/CC1150/CC2500/CC251x/CC2550 by 611949
When [PREAMBLE+SYNC] auto-generation is enabled (MDMCFG2.SYNC_MODE = 1, 2, 3, 5, 6 or 7), the radio will automatically send[PREAMBLE+SYNC] before it outputs the packet payload + optional CRC. To obtain the recommended [PREAMBLE+SYNC] pattern/length use SmartRF Studio. The PREAMBLE pattern is fixed = 10101010 bin = AA hex, while the SYNC pattern is programmable through theSYNC0/1 registers. The standard PREAMBLE configurations are 2, 3, 4, 6, 8, 12, 16, or 24 bytes (MDMCFG1.NUM_PREAMBLE), and thestandard SYNC configurations are 0, 2, or 4 bytes (MDMCFG2.SYNC_MODE). Note that for SYNC configuration = 2 bytes, the radio willoutput [SYNC1+SYNC0], while for SYNC configuration = 4 bytes, the radio will output [SYNC1+SYNC0+SYNC1+SYNC0].Setting the initial SYNC pattern partly identical to the PREAMBLE pattern allows for custom [PREAMBLE+SYNC] patterns/lengths.For instance, SYNC configuration = 2 bytes (MDMCFG2.SYNC_MODE = 1) and [SYNC1] = [PREAMBLE pattern (AA hex)] effectively"extends" the PREAMBLE pattern by 1 byte and shortens the SYNC pattern accordingly. Choosing PREAMBLE configuration = 2 bytes(MDMCFG1.NUM_PREAMBLE = 0), then makes the effective PREAMBLE pattern 3 bytes, while the effective SYNC pattern becomes 1 byte.The radio can thus offer the following custom lengths of [(PREAMBLE+SYNC1) + SYNC0]:[(2+1) + 1], [(3+1) + 1], [(4+1) + 1], [(6+1) + 1], [(8+1) + 1], [(12+1) + 1], [(16+1) + 1], or [(24+1) + 1] bytes.
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